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Wildlife management and conservation requires monitoring of species distribution and population indicators, especially when the unbalanced demographic changes of some species can affect the whole ecosystem functioning. The populations of wild boar (Sus scrofa) have, over the past few decades, undergone an expansion around the world, reaching situations of overabundance that can cause serious economic, ecological and health problems. This numerical increase of wild boar and its new spatial invasion can affect certain vulnerable species in sensitive ecological zones, such as the main inland wetland complex in SW Europe. In this context, we aim to (i) examine the association of wild boar abundance and that of lagomorphs, and waterbird productivity, controlling the possible effects of wild carnivores and other environmental predictors, and (ii) applying a survey method useful for managers to evaluate expected effect of wild boar abundance. Overall, the presence of wild boar has been detected in 80.8% of the monitored wetlands (n = 26), but a high variation of abundance rates was found. Wild boar abundance negatively associated with the productivity of the entire community of waterbirds, a priori highly vulnerable, breeding on shores or islands, both colonially (genus Gelochelidon, Himantopus, Recurvirostra, Sternula, Glareola, Tringa and Phoenicopterus) or solitary (genus Anas, Spatula, Mareca, Charadrius, Vanellus, Anser, Ardea, Aythya, Fulica, Netta, Oxyura and Tadorna). In addition, we evidenced a clear negative association of wild boar and wild rabbit (Oryctolagus cuniculus) population abundance in the monitored wetlands. Rabbits are a keystone species in the study area and represent stable prey for many endangered predators. Our results suggest that potential impacts caused by high wild boar abundance may be already reaching unsustainable levels for some wetlands. Inter-species integrated monitoring is key to address the population management plans of wild boar populations in wetlands and to preserve the most vulnerable species., The present work has benefited from financial support of LIFE project “Humedales de la Mancha”. JAB and AJC were supported by a “Juan de la Cierva” contract (FJCI-2015-23643 and FJCI-2017-33114) from MINECO-UCM and MINECO-UCLM, respectively.

This article belongs to the Special Issue Zoonoses and Wildlife: One Health Approach., Coxiella burnetii, the causal agent of human Q fever and animal Coxiellosis, is a zoonotic infectious bacterium with a complex ecology that results from its ability to replicate in multiple (in)vertebrate host species. Spain notifies the highest number of Q fever cases to the ECDC annually and wildlife plays a relevant role in C. burnetii ecology in the country. However, the whole picture of C. burnetii hosts is incomplete, so this study seeks to better understand the role of micromammals in C. burnetii ecology in the country. Spleen samples from 816 micromammals of 10 species and 130 vaginal swabs from Microtus arvalis were analysed by qPCR to detect C. burnetii infection and shedding, respectively. The 9.7% of the spleen samples were qPCR positive. The highest infection prevalence (10.8%) was found in Microtus arvalis, in which C. burnetii DNA was also detected in 1 of the 130 vaginal swabs (0.8%) analysed. Positive samples were also found in Apodemus sylvaticus (8.7%), Crocidura russula (7.7%) and Rattus rattus (6.4%). Positive samples were genotyped by coupling PCR with reverse line blotting and a genotype II+ strain was identified for the first time in one of the positive samples from M. arvalis, whereas only partial results could be obtained for the rest of the samples. Acute Q fever was diagnosed in one of the researchers that participated in the study, and it was presumably linked to M. arvalis handling. The results of the study are consistent with previous findings suggesting that micromammals can be infected by C. burnetii. Our findings additionally suggest that micromammals may be potential sources to trace back the origin of human Q fever and animal Coxiellosis cases in Europe., This work was supported by grants CGL2011-30274 and CGL2015-71255-P of the Spanish Ministry for the Science and Innovation (MCI), and by the ‘Fundación BBVA’ Research Project TOPIGEPLA (2014 call). This is also a contribution to MCI-funded projects CGL2017-89866-R and E-RTA-2015-0002-C02-02. D.G.-B. was funded by MCI through Juan de la Cierva (FJCI-2016-27875) and ‘Sara Borrell’ (CD19CIII/00011) postdoctoral fellowships. GREFA provided partial financial support and invaluable logistic and workforce support for samplings in NW Spain, along with many students and staff from UAM.

Although roads are widely seen as dispersal barriers, their genetic consequences for animals that experience large fluctuations in population density are poorly documented. We developed a spatially paired experimental design to assess the genetic impacts of roads on cyclic voles (Microtus arvalis) during a high-density phase in North-Western Spain. We compared genetic patterns from 15 paired plots bisected by three different barrier types, using linear mixed models and computing effect sizes to assess the importance of each type, and the influence of road features like width or the age of the infrastructure. Evidence of effects by roads on genetic diversity and differentiation were lacking. We speculate that the recurrent (each 3–5 generations) episodes of massive dispersal associated with population density peaks can homogenize populations and mitigate the possible genetic impact of landscape fragmentation by roads. This study highlights the importance of developing spatially replicated experimental designs that allow us to consider the large natural spatial variation in genetic parameters. More generally, these results contribute to our understanding of the not well explored effects of habitat fragmentation on dispersal in species showing “boom-bust” dynamics., This study was funded by I+D National Plan Projects of the Spanish Ministry of Economy, Industry and Competitiveness (TOPILLAZO-CGL2011-30274 and MOVITOPI-CGL2015-71255-P), Fundación BBVA Research Project TOPIGEPLA (2014 call) and MAPAMA/TRAGSATEC to GREFA (biological control program). Julio C. Dominguez was supported by a predoctoral grant: “Programa Talento Formación” funded by Fondo Social Europeo (FSE) and Castilla La Mancha regional government (JCCM) (ref:SBPLY/16/180501/000205).

Parent–offspring conflict theory predicts that offspring seek to prolong the parental care period, while parents strive to shorten it as much as possible. Transition to the crèche phase in penguins involves changes in the dynamic of parental investment in chicks, and thus may be modulated by interests that benefit parent or offspring. We explored parent–offspring interactions in the Chinstrap Penguin (Pygoscelis antarctica) to understand the influence such interactions would have on transition to crèche phase. We studied the effect of hatching date, nestling age, brood size, and nest location on parent–offspring interactions and the length of the guard phase. All behavioral variables related to nestling demands for parental investment increased as well as parental aggression towards their chicks, with increased nestling age. Brood size showed significant effects on both nestling and parental behavior. Hatching date was negatively correlated with the age at crèche. Consequently, the decision to leave the chicks unguarded seemed to be more based on the condition of adults rather than of the chicks. Given the short time available for breeding in Antarctica and that penguins are long-lived birds with several opportunities to breed, there may be conflicting selective factors between investment in feeding chicks versus extending the period of resource acquisition and storage prior to moult., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.

Toxicants such as organochlorine insecticides, lead ammunition, and veterinary drugs have caused severe wildlife poisoning, pushing the populations of several apex species to the edge of extinction. These prime cases epitomize the serious threat that wildlife poisoning poses to biodiversity. Much of the evidence on population effects of wildlife poisoning rests on assessments conducted at an individual level, from which population-level effects are inferred. Contrastingly, we demonstrate a straightforward relationship between poison-induced individual mortality and population changes in the threatened red kite (Milvus milvus). By linking field data of 1,075 poisoned red kites to changes in occupancy and abundance across 274 sites (10 × 10-km squares) over a 20-y time frame, we show a clear relationship between red kite poisoning and the decline of its breeding population in Spain, including local extinctions. Our results further support the species listing as endangered, after a breeding population decline of 31% to 43% in two decades of this once-abundant raptor. Given that poisoning threatens the global populations of more than 2,600 animal species worldwide, a greater understanding of its population-level effects may aid biodiversity conservation through increased regulatory control of chemical substances. Our results illustrate the great potential of long-term and large-scale on-ground monitoring to assist in this task., Hundreds of volunteers and personnel from Spanish autonomous governments (Comunidades Autonomas [CCAA]) participated in the national census of red kites, organized by SEO/Birdlife, with financial support from the Royal Society for the Protection of Birds, the Spanish Ministry of Environment (SME), and CCAA. The database of poisoned animals was compiled by CCAA and SME and coordinated by WWF Spain and SEO/Birdlife through the ANTÍDOTO program. This work was funded by WWF Spain under project UCLM-UCTR170245, and by the BBVA Foundation (“Ayudas Fundación BBVA a Equipos de Investigación Científica 2018”) through the TÓXICO project.

It is known that the garden dormouse Eliomys quercinus includes meat in its diet, however, it is unclear if scavenging is a widespread behaviour, as it is difficult to observe in the wild. Here, we document scavenging behaviour for the species based on direct evidence. We captured five garden dormice with live traps using dead baits, which were partially or totally consumed. Additionally, a camera-trap recorded how at least one garden dormouse visited and actively consumed the bait on 12 occasions during the study. These observations suggest that carrion may play an important role in the garden dormouse's diet, opening a new ecological unexplored topic for this species., This study was funded by projects TOPIGEPLA (Fundación BBVA Research Projects, 2014 call) and Movi-Topi (I + D National Plan Project, CGL2015-71255-P). F. Díaz-Ruiz was supported by a “Juan de la Cierva” research contract (Ministerio de Ciencia e Innovación, Funder Id: 10.13039/501100004837, FJCI-2015-24949) from the Spanish Ministry of Economy, Industry and Competitiveness.

Understanding spatiotemporal variations of movements and habitat selection by animals living in changing, heterogeneous environments under increasing human pressure is crucial for biodiversity conservation. We report here on shifts in habitat selection and movements during the breeding and non-breeding periods in a vulnerable and specialist bird, the pin-tailed sandgrouse Pterocles alchata, to understand the importance of remnant natural or semi-natural habitats. We used a 7-year dataset from 91 radio-tracked birds living under two contrasting landscapes: a farmland-dominated area (agricultural landscape) in central Spain and a low-intensive farmland area with natural steppe-like vegetation (mixed landscape) in northern Spain. We found that sandgrouse selected sites of natural vegetation (short shrubs and sparse annual plants) across all periods in the mixed landscape. Birds performed long movements in the agricultural landscape to exploit patchy resources and expanded their distribution during the breeding period, possibly because of an increased scarcity of non-cropped habitats in farmland. During the non-breeding period, sandgrouse used dry arable lands in both landscapes, with birds in the mixed landscape displaying a highly mobile pattern to visit dry arable regions. Dry arable lands become structurally more suitable during winter for seed-eating birds such as sandgrouse that can use ploughed fields and exploit seeds during cereal sowing. Effective conservation measures for specialist birds of farmland should promote a greater availability of non-cropped habitats of natural and semi-natural vegetation to enhance their space use and reproductive opportunities., MINECO [CGL2007-66322/BOS and CGL2008-04282/BOS], Junta de Comunidades de Castilla-La Mancha [PAI08-0171-9582, PAC06-137 and SBPLY/17/180501/000245] and Bardenas Reales Biosphere Reserve [UCTR09-0268, UCTR110053 and UCTR120308]. Juan de la Cierva-Formación [FJCI-2016-28540] to RT and Juan de la Cierva-Incorporación [IJCI-2017-31419] to ABL, Torres Quevedo [PTQ-17-09549] to FC and I3P-CSIC to CAM.

Biological control of rodents in agricultural areas, increasing avian predator abundance by nest-box provisioning, has been proposed during the last decades in several regions around the world as an alternative to the widespread use of anticoagulant rodenticides (AR) to protect crops. However these experiences have often lacked a “Before-After-Control-Impact” (BACI) experimental design providing evidence strong enough about their efficacy reducing vole abundance or crop damages. Furthermore, little is known about possible indirect effects on non-target species. Here we test the effectiveness of providing nest-boxes to common kestrels (Falco tinnunculus) and barn owls (Tyto alba) in reducing the abundance of two different vole species using indirect index methods to estimate rodent abundance in late spring (May). We monitored the abundance of both vole species in a treatment (with nest boxes) and control (without nest boxes) areas during three years in alfalfa fields, using a BACI design. We studied also the efficiency of this control method in three different crops (alfalfa, cereal and fruit-trees) during the last year of the experiment. We compare the results obtained in this study area in NE Spain with those obtained simultaneously in other three experimental areas in NW Spain. Finally we explored potential negative effects of this method on the abundance of several passerine birds present in our research area. Our results showed a clear-cut reduction in the abundance of the two vole species, the common vole (Microtus arvalis) and the mediterranean-pine vole (Microtus duodecimcostatus) in the experimental area after applying the treatment (nest box installation) in alfalfa crops. We also found a significant decrease in the presence of both species of voles on fruit-tree plantations and alfalfa crops but we did not find significant effects in the cereal fields, where voles were in general very scarce. These results suggest higher efficacy of biological control in this study area than in some areas of NW Spain, what could be explained by several non-exclusive hypotheses presented in the discussion. For other species, we found a negative effect of nest-boxes on the abundance of a limited number of common bird species, but also positive effects over other species using poles with nest-boxes as perches. In conclusion, under the conditions of our study area, nest-box provisioning seemed to be an effective technique to reduce vole abundance, but also had some undesired side-effects on non-target species. However, these side-effects affected mainly to common bird species and can thus be considered less relevant than those caused by SGARs, often affecting to endangered rodent predators and that could thus have negative effects over any potential future natural control of vole abundance, potentially increasing future needs of SGAR use in a vicious circle., This study contributes to the research projects TOPIGEPLA, funded by BBVA Foundation and MOVITOPI (CGL2015-71255-P) funded by the Ministerio de Economía y Competitividad of Spain.

Productivity (offspring production) is a key demographic parameter influencing population dynamics, particularly in r-strategy species, and thus critical for implementing well-based management of populations. Accordingly, the study of factors influencing productivity is useful to develop management strategies in species of conservation concern or subject to exploitation. We studied productivity (covey size and young/adult ratio) of red-legged partridges (Alectoris rufa) in Spain through a large-scale sampling in Andalucia and Castilla-La Mancha, two large areas in central-southern Spain, the core of the distribution of the species. We evaluated potential environmental factors related with productivity that have been considered important in previous local studies (weather, land use, and intensity of releases of farm-reared partridges), using a dataset of 15,357 observations of partridges over three breeding seasons (2010, 2011, and 2012). Average productivity at the end of July was 3 young/adult, indicating 50% chick mortality between hatching and fledging and high breeding failure. We found marked effects of weather, year, and land use on partridge productivity, confirming some previous results at local scale and supporting widespread and simultaneous effects of these factors. We also detected a large-scale negative relationship with farm-bred partridge release intensities, with lower young/adult ratios in areas with high release intensity. This suggests that partridge releases may be contributing to the decline of wild populations. Our results support that correcting the effects of agricultural intensification is the main key to the long-term conservation of the species and suggest that, in dry spring years (leading to low average productivity), many populations could be exposed to overhunting. These results stress the importance of both small- and large-scale adjustments of hunting pressure to partridge productivity, in order to preserve wild populations. Poor hunting bags in “bad” years, along with the increasing demand in the hunting market, may have stimulated the widespread use of releases, further reducing productivity and leading to the current compromised conservation status of wild populations. We discuss some potential solutions to this conflicting situation from the socioeconomic and environmental points of view., This work has been made possible by the Project: “Monitoring for the determination of egg-laying dates of red-legged partridge Alectoris rufa” funded by the Regional Governments of Castilla-La Mancha and Andalucia.

[EN]: For pest management strategies to effectively prevent crop damage while at the same time causing the least environmental collateral damage, reliable abundance monitoring tools are required. The common vole is a major agricultural pest in Castilla y León (NW Spain). In this study we compared common vole density estimates provided by two indirect indices, the Presence Signs per Square (PSpS) index, previously evaluated by a comparison with the trapping methodology most accepted to estimate rodent densities, and another one (MI), proposed by the Spanish Ministry of Agriculture Food and Environment, which is currently recommended as main monitoring tool for this pest, but that apparently has not been evaluated in a similar way. We found that at low vole abundance, MI generated much larger vole density estimates (on average 14 times) as compared to PSpS, although both indices were highly correlated. These results strongly support that abundance estimates provided by MI must be considered potential overestimates of real vole density and must be corrected accordingly in the future, if the method is to be kept as a main monitoring tool of vole density. Our results reinforce the importance of evaluating this kind of monitoring tools in different density scenarios to prevent the start or continuation of control campaigns when they are unnecessary, thus reducing their associated economic and environmental costs., [ES]: Uno de los aspectos más importantes a la hora de mejorar la gestión de plagas y reducir de forma eficaz los daños que causan en cultivos, minimizando a su vez los daños colaterales causados al medio ambiente, es disponer de herramientas de monitorización fiables. El topillo campesino es una de las plagas agrarias mas importantes en Castilla y León (NO de España). En el presente estudio se compararon las estimaciones de densidad del topillo campesino obtenidas mediante dos índices indirectos: el índice PSpS (Presence Signs per Square) previamente evaluado con la metodología de trampeo considerada mas fiable para estimar densidades de roedores, y el índice MI propuesto por el Ministerio de Agricultura, Alimentación y Medio Ambiente, recomendado como principal herramienta de monitorización de dicha especie, pero para el que no existe aparentemente ninguna evaluación de precisión o eficacia. En condiciones de baja abundancia de topillo campesino se observó que el índice MI estimaba densidades de topillos muy superiores a las proporcionadas por el índice PSpS (14 veces mayores en promedio), aunque ambos índices estaban altamente correlacionados entre sí. Estos resultados indican que el índice MI tiene una alta probabilidad de sobreestimar la abundancia de topillos en condiciones de densidad baja. En conclusión, las estimaciones de abundancia obtenidas con el índice MI deben ser consideradas como sobreestimaciones potenciales de la densidad real del topillo campesino, debiendo ser corregidas si se quiere mantener dicho índice como la principal herramienta para monitorizar las poblaciones de topillo campesino. Los resultados obtenidos refuerzan la importancia de evaluar la eficacia y precisión de este tipo de herramientas, para reducir el riesgo de realizar campañas de control innecesarias, minimizando así los costes económicos y ambientales asociados a las mismas., This research was funded by the ERA-Net BiodivERsA, with the national funders MICINN, MEEDDTL, NERC and RCN, as part of the 2007 BiodivERsA call for research proposals through project Ecocycles. D.J. enjoyed a PhD grant JAE Predoc, from the CSIC, jointly funded by the European Social Fund. This study also contributes to the projects TOPILLAZO (CGL2011-30274/BOS), funded by the Ministerio de Economía y Competitividad of Spain, and TOPIGEPLA, funded by BBVA Foundation.

BACKGROUND Vole outbreaks have been extensively described, along with their impacts on humans, particularly in agricultural areas. The use of rodenticides is a common legal practice to minimise crop damage induced by high vole density for biocidal use. However, rodenticides can have negative direct and indirect impacts on non-target species that feed on voles. We studied whether the use of a second-generation anticoagulant rodenticide (SGAR), bromadiolone, can be detected in the blood of fledglings of wild common kestrels Falco tinnunculus in two areas of central Spain, exploring its possible indirect effects. RESULTS We found that 16.9% of fledglings had a detectable concentration of bromadiolone in their blood, with an average concentration of 0.248 ± 0.023 ng mL−1. Fledglings with bromadiolone in their blood, regardless of the concentration, had 6.7% lower body mass than those without detectable bromadiolone. CONCLUSION The use of bromadiolone was detectable in the blood of alive non-target species. Detected bromadiolone in blood may reduce the body condition of nestlings, potentially reducing their fitness. The source of bromadiolone found in nestlings needs to be determined in future studies to derive accurate management advice. However, we urge the discontinuation of official SGAR distribution to farmers and their use in agrarian lands to minimise damage of voles on crops, particularly where common kestrels breed, and encourage the use of alternative effective practices. © 2016 Society of Chemical Industry

Understanding how species respond to disturbance in human-modified ecosytems is critical for management and conservation of biodiversity in the Anthropocene. In agroecosystems, human disturbances severely modify the habitat of species, particularly for those that live in burrows. The common vole Microtus arvalis (Pallas, 1778) is a semi-fossorial microtine, which often exhibits large abundance fluctuations, becoming an agricultural pest in peak years. We evaluated how both agrarian disturbances (via types of crop and their management) and landscape heterogeneity influenced the abundance of common vole burrow systems along a yearly cycle, at the field and landscape scales. We seasonally recorded the number of burrows and their recent occupation in circular plots of 200-m radius including different types of crops in intensified agrarian landscapes in NW Spain. Our results showed a marked seasonal and spatial pattern in both total abundance and abundance of occupied burrows. After a population peak year, only 31% of burrows were occupied across the year (from 41% in spring–summer to 12% in autumn). The crop type and its management in relation to soil disturbance were the main factors driving seasonal and spatial dynamics of burrow abundance at the field and landscape scale. Alfalfa fields held the highest abundance of both total and occupied burrow systems across the year, while fields of traditional-tilled cereal retained the lowest. As a result, at the landscape scale, plots with a greater surface devoted to traditional cereal crops maintained a lower relative number of burrow systems. Regarding the landscape structural heterogeneity, plots with longer length of field margins and lower area of watercourses maintained higher abundance of burrow systems. An adequate landscape-scale planning of crop types, agricultural practices, and distribution of non-crop habitats could be a promising sustainable method to reduce the risk of crop-damaging vole plagues., This study was funded by I+D National Plan Projects of the Spanish Ministry of Economy, Industry and Competitiveness (CGL2011-30274 and CGL2015-71255-P), and the Fundación BBVA Research Project TOPIGEPLA (2014 call).

In conservation biology, population monitoring is a critical step, particularly for endangered groups, such as steppe birds in European agro-ecosystems. Long-term population monitoring allows for determination of species population trends and also provides insights into the relative roles that environmental variability and human activities have on priority species. Here, we compare the population trends of two sympatric, closely related farmland bird species, the Little Bustard Tetrax tetrax and Great Bustard Otis tarda, in a protected area of Central Spain, which is their main stronghold in Europe. Over 12 years of monitoring, the abundance of Little and Great Bustards shifted in opposite directions in our study area. Little Bustard abundance decreased significantly (both males [-56%], and harder-to-detect females [-55%]), while Great Bustard abundance increased significantly (1,800%). Future surveys should be more precise and frequent for Little Bustards to facilitate evaluation of their population status and trends. We recommend annual surveys in 2-3 important locations by region throughout the breeding range for Little Bustards, while for Great Bustard the current regional monitoring programmes would be sufficient., This work was supported by the Ministerio de Ciencia y Tecnología (MCYT-REN2003-07851/GLO, CGL2004-02568/BOS, CGL2007-66322/BOS and CGL2008-04282/BOS) and the Project ‘‘Steppeahead’’ funded by Fundación General del Consejo Superior de Investigaciones Científicas from Spain (FGCSIC) and Banco Santander. FC was supported by the Andalucía Talent Hub Program launched by the Andalusian Knowledge Agency, cofounded by the European Union’s Seventh Framework Program, Marie Skłodowska-Curie actions (COFUND–Grant Agreement n° 291780) and the Ministry of Economy, Innovation, Science and Employment of the Junta de Andalucía.

Complex body designs, such as plumage ornaments in birds, can be described by fractal geometry. These complex patterns could have a role as visual signals during courtship and social interactions, but an empirical validation in the wild is currently lacking. Here, we investigated whether the fractal dimension (FD) of a complex plumage pattern displayed by red-legged partridges Alectoris rufa could function as a potential sexual signal. We captured wild birds early in the breeding season and tested if mated and unmated birds differed in the FD of their conspicuous melanin-based black bib. We also tested if the FD of the black bib was correlated within the pair, looking for evidence of assortative mating based on the expression of this trait. We simultaneously assessed similar effects in other ornamental traits (black bib size, white throat patch and black flank band surface, redness of the eye rings and bill). Mated birds showed higher black bib FD values than unmated ones. Mated males, but not females, also displayed a larger black bib. Moreover, the black bib FD (but not the trait size) and the white throat patch surface showed assortative mating. Finally, females with higher black bib FD showed smaller black flank band surface, suggesting a trade-off in the expression of the two melanin-pigmented plumage traits. This provides unique and novel indication for the shape complexity of a pigmented trait, here described by its fractal dimension, to be potentially under sexual selection in a wild animal., A.C. was funded by a Juan de la Cierva-formación postdoctoral grant (FJCI-2015-23536; Ministerio de Economía, Industria y Competitividad, MINECO). Financial support was obtained from the projects PII1I09-0271-5037, PII1C09-0128-4724 and SBPLY/17/180501/000468 from the JCCM and CGL2009-10883-C02-02 from Ministerio de Ciencia e Innovación (Spain). F.C. was supported by the University of Maryland.

In Europe, hunting and game management are centuries-old activities that have had profound effects on the landscapes and the biodiversity they support. Game management is a potentially important tool to enhance game populations and may also affect other wildlife. We investigated the relationship between red-legged partridge Alectoris rufa game management and steppe-bird abundance in central Spain. We surveyed 54 red-legged partridge hunting estates with varying game-management intensity in spring and/or summer in 2006 and 2008–2010. Information about game management was gathered through questionnaires to game managers. Birds were counted from fixed points and the amount of different land uses in each point was visually estimated. Our results show that the abundance of granivorous species (sandgrouse) increased significantly with the density of feeders, whereas non-granivorous species were more abundant in estates with more intensive fox control, although the latter relationship was weaker. Land-use variables, specifically agricultural lands, appeared in the models of all the groups considered. Therefore, there is an option for designing optimal management for red-legged partridge estates that potentially benefits non-target species: an effective combination of habitat management, adequate use of supplementary food and water, and possibly selective legal predator control when necessary and effective for the target game species, although the latter needs further investigation.

The common vole, considered a rodent pest when overabundant in agricultural areas, was traditionally absent from the agricultural plains of Castilla-y-León, NW Spain. However, it rapidly invaded ca. 50.000 km2 of agricultural land, where regular outbreaks have caused crop damages and conflict with farmers. To better understand the factors that triggered this massive invasion of previously unoccupied habitats, we studied the associations between the common vole range expansion and changes in climate and land uses in the region since the 1970s. We found long-term trends in climate, with some changes that could have helped the range expansion (increased fall precipitation and winter temperature) and other changes that may have impaired it (reduced summer precipitation and increased summer temperatures). Dramatic changes in land use also took place prior to and during the invasion period (marked increases in irrigated and green herbaceous crops such as alfalfa, which are preferred habitats for voles). We found strong associations between changes in vole distribution and the extent of green crops (irrigated crops and alfalfa) at regional level. The colonization probability of a given agrarian county increased with the extent of green crops, particularly so when vole presence in neighbouring counties was lower, and tended to decrease with increasing livestock abundance. Land use changes, especially increases in irrigated crops and alfalfa, appear to be amongst the main drivers behind the vole range expansion. We discuss these findings in relation to the social conflicts and management challenges that arose from the recent invasion of agricultural areas by crop-damaging common voles., Funding was from the ECOCYCLES project (BIODIVERSA. ERA-net project, European Union´s 6th Framework Programme for Research); PhD grant JAE-Predoc, from the CSIC, jointly funded by the European Social Fund to DJ. This study also contributes to projects ECOVOLE (CGL2012-35348) and TOPILLAZO (CGL2011-30274/BOS) funded by the Ministerio de Economía y Competitividad of Spain.

A significant restructuring of vineyards is currently taking place in the European Union (EU) as a result of the implementation of a restructuring and conversion of vineyards regulation (CE 1493/1999) in southwest Europe, so that trellis vineyards are rapidly replacing traditional vineyards (e.g., surface area from 18.1 % in 2010 to 34 % in 2015 in Castilla-La Mancha, Central Spain). These changes may influence patterns of space use in birds, which may avoid modified habitats. We assess how the location of traditional and trellis vineyards might influence the distribution of great bustard (Otis tarda), a globally threatened species. We estimate Resource Selection Functions (RSFs) to quantify the relative probability of use of different areas by the great bustards, and use the RSF’s to simulated scenarios of conversion from traditional to trellis vineyards (low - 10 %, medium - 30 %, and high rate - 60 %) to quantify the potential impact of such modifications on the availability of suitable great bustard habitat. Our results revealed that great bustards significantly avoid trellis vineyards, especially at closer distances. Transition scenarios show how an increase in the proportion of traditional vineyards converted to trellis vineyards greatly decrease the proportion of suitable habitat for great bustard. Compared to current conditions, the percentage loss of suitable habitat increased steadily with higher rates of converted vineyards, up to 60 % loss of suitable habitat at the highest rate of conversion. Because the effect of transforming traditional vineyards to trellis vineyards depends both on the amount of habitat available for bustards before the transformation occurs and on the overall area covered by vineyards, a correct estimation of transformable vineyard area will require a case-by-case assessment to assure a low impact on bustard populations. We identified alternative vineyard management options that would mitigate impacts on the great bustard populations., This work was supported by the Ministerio de Ciencia y Tecnología (MCYT-REN2003-07851/GLO and CGL2004-02568/BOS). FC was supported by the Andalucía Talent Hub Program launched by the Andalusian Knowledge Agency, cofounded by the European Union’s Seventh Framework Program, Marie Skłodowska-Curie actions (COFUND–Grant Agreement n° 291780) and the Ministry of Economy, Innovation, Science and Employment of the Junta de Andalucía, and by the University of Maryland.

In southern Europe, traditional hunting has been frequently replaced by models based on more intensive management. These systems include management strategies like the release of farm-reared animals that can cause harmful effects on biodiversity. However, little is known about the hunters’ views of this activity, and about their preferences for the ecological attributes of the hunting estates. We present the results of a choice experiment exercise evaluating the willingness to pay of Spanish hunters regarding different aspects of walked-up red-legged partridge (Alectoris rufa) shooting, including partridge quality (farm-reared vs. wild) and other attributes related to the ecological characteristics of the estate. We find that, when given the choice, hunting an additional wild partridge in a walked-up shooting day was valued more than 20 times higher than hunting an additional farm-reared bird. The diversity of small game available and the presence of natural vegetation in the landscape in which the walked-up hunting takes place were also significantly valued. Hunters also attributed economic value (albeit lower than other attributes) to the presence of protected non-game fauna in the estate. Overall, our results show that hunters are willing to pay more for hunting on estates that have better ecological characteristics, which may be indicative of good conservation status. This suggests that identifying and promoting such estates could lead to systems that are both ecologically and economically sustainable., This work was supported by the European Commission under the 7th FWP for Research and Technological Development, project HUNT (212160, FP7-ENV-2007-1). M. D-M. is currently supported by a JAE-DOC contract (Programa Junta para la Ampliación de Estudios), funded by CSIC and the European Social Fund (ESF). J.C. had a postdoctoral contract jointly funded by the ESF and by the Junta de Comunidades de Castilla–La Mancha (Spain), Operational Programme FSE 2007–2013.

Irruptive populations of rodents cause damage to agriculture worldwide. By the end of the last century, the distribution range of Microtus arvalis in NW Spain greatly expanded to encompass agricultural habitats, with the appearance of crop damaging population outbreaks. The absence of long term vole monitoring data has so far precluded outbreak forecasting, which might help mitigating associated bioeconomic costs. We used non-standard and diverse sources of information, including newspaper and national technical reports, to describe the vole expansion and outbreak dynamics in NW Spain since the late 1960s. We illustrate a rapid (40 years) regional scale vole dynamics reported for the Iberian Peninsula. We suggest that expansion from (humid) mountains to (dry) plains may be related to recent changes in land use. If confirmed at a local scale, the apparent cyclicity of outbreaks would provide a basis for forecasting outbreak risk in NW Spain and may help managers adjust current control strategies., Financial support was provided by ECOCYCLES project (BIODIVERSA 2008, Era-net European project, EUI2008-03658 and NERC NE/G002045/1). This study also contributes to the project ECOVOLE (CGL2012-35348; Ministerio de Economía y Competitividad of Spain).

In the last decades, the release of large numbers of farmed-reared birds became a widespread management practice for game species. The red-legged partridge (Alectoris rufa) is a quarry species with a high economic impact in rural areas of southwest Europe. In order to increase productivity and produce heavier birds, farmed red-legged partridges have often been hybridized with Chukar partridges (A. chukar), although these species have allopatric distribution ranges. During restocking, hybrid birds may be released into wild populations and may subsequently successfully breed, thus threatening the genetic integrity of native A. rufa populations. In this study, we compared several phenotypic indicators (body size, body condition and physiological state) between >pure> and hybrid partridges in order to evaluate the possible consequences of A. chukar genetic introgression into A. rufa. For this purpose, we captured 115 wild red-legged partridges during the breeding seasons 2003-2005 in four game estates of central Spain. We observed a greater occurrence of hybrid A. rufa × A. chukar partridges nearby the sites where the release of farmed-birds took place. We also found that hybrid males were smaller and hybrid females had better body condition and lower plasma carotenoid concentration than pure partridges of the same sex. Low carotenoid levels in blood plasma might be a limitation for female reproduction (fewer carotenoids available for ornamentation or to allocate to eggs). Overall, our results showed a greater occurrence of hybrids near restocking areas and phenotypic differences between hybrids and >pure> partridge in the wild. Genetic controls of farm-reared partridges should be a key step to prevent the releases of hybrids and ensure the maintenance of the genetic integrity of wild red-legged partridge populations., Fabián Casas was supported by a post-doctoral grant of the Junta de Comunidades de Castilla la Mancha (JCCM), and a JAE-Doc contract of the program «Junta para la Ampliación de Estudios» financed by the European Social Fund (ESF). This work alsoreceived a grant by the research project ‘‘Bases científicas preliminares para un plan de conservación de la perdiz roja en Castilla-La Mancha’’ of the Consejería de Agricultura y Medio Ambiente de la JCCM (Junta de Comunidades de Castilla-La Mancha), and CYCIT projects MCYT-REN200307851/GLO and CGL2004-02568/ BOS. FM was supported by a Grant from the Ministerio de Educación y Ciencia, Spain (CGL 2006-11823) and from the JCCM, Spain (PAI06-0112).

Habitat selection is an inherently scale-sensitive process in which detected selection patterns frequently depend on the scale of analysis employed. We used a multi-scale modelling approach to identify how the distributions of two sympatric birds are shaped by differential selection at the landscape, land use and microhabitat scales and by human infrastructures as possible sources of disturbance. We studied two threatened steppe birds, the pin-tailed sandgrouse (PTS) and black-bellied sandgrouse (BBS) in central Spain. Land use gradients explained most of the variation in PTS and BBS occurrence, but there was cross-scale interdependence between the lower (microhabitat) and upper (landscape) spatial scales for the PTS. Synergies between the three scales highlighted the importance of integrating habitat scales in a single modelling framework. The process of habitat selection was also modulated by human disturbance. Both species selected ploughs of large size distant from houses, tracks and other infrastructures, although BBS exhibited broader habitat tolerance than the PTS, and was more sensitive to human disturbance. At microhabitat scale, PTS selected ploughs with greater green vegetation cover and insect abundance and fallows with lower dry vegetation cover and height but greater stone cover. This might reflect a trade-off between camouflage (vegetation and stone cover for concealment) and visibility for predator detection and escape. Ploughs and fallows should be maintained by means of traditional 2-year rotations and low management during the breeding season. Ongoing urbanization trends and infrastructure development inside protected areas should be limited. Multi-scale models were key to identify scale-specific factors that determine sandgrouse habitat preferences and conservation requirements at appropriate levels, and are recommended to better guide regional and local conservation efforts of threatened species., This study is a contribution to the CGL2008-04282/BOS Project funded by the Spanish Ministry of Science. A. Benítez-López was supported by the CGL2008-04282/BOS Project and by the 2012-BIN-4462 research Grant conceded by the UCLM. F. Mougeot was supported by a distinguished visitor award from the University of Cape Town (2015).

[ES]: Recopilamos el conocimiento científico actual sobre la ecología y gestión cinegética de la perdiz roja, haciendo hincapié en los hallazgos de los últimos años. La perdiz roja es una especie cinegética muy apreciada, cuyo estatus de conservación ha sido, y probablemente es, delicado. En los cotos de caza menor se dedican grandes esfuerzos a su gestión, pero muchas prácticas se aplican sin conocer las consecuencias que tienen para las poblaciones de perdiz. Los estudios revisados indican que el modelo de gestión más adecuado para aumentar la abundancia de esta especie, manteniendo la integridad biológica de sus poblaciones al tiempo que se cazan, incluye un ajuste apropiado de la presión cinegética a la abundancia anual de perdices, el manejo del hábitat promoviendo la vegetación natural en la matriz agrícola y la presencia de lindes, y el aporte suplementario de agua y comida. La información sobre la eficacia del control legal de depredadores generalistas para incrementar la abundancia de perdiz no es concluyente. Las sueltas de perdices de granja ponen en riesgo la integridad genética de la especie. Además, cuando se sueltan en pequeñas cantidades, no aumentan las bolsas de caza ni la rentabilidad económica de los cotos, pero afectan negativamente a la productividad de las poblaciones silvestres de perdices. A pesar del ocio y movimiento económico que genera la caza de perdiz roja, una gestión inadecuada reduce los beneficios potenciales de la actividad., [EN]: We review scientific knowledge on red-legged partridge ecology and management, focusing on recent studies. Red-legged partridge is a greatly valued game species, whose conservation status has been, and probably still is, poor. In small-game hunting estates, great efforts are devoted to red-legged partridge management, but many practices are applied without knowing their real consequences for partridge populations. Reviewed studies show that the most successful management options to increase the abundance of the species, allowing a sustainable harvest, would include an adequate adjustment of annual harvest to partridge abundance, appropriate habitat management promoting the presence of natural vegetation within the farmland matrix and field edges, and water and food supplementation. Information about the efficacy of predator control to increase red-legged partridge abundance is inconclusive. Releases of farm-reared partridges are putting at risk the genetic integrity of the species. Furthermore, when few partridges are released, releases do not increase annual harvest or estate profitability, and negatively affect the productivity of wild red-legged partridges. Despite leisure and economic movement generated by red-legged partridge hunting, inadequate management is currently reducing the potential benefits of this activity.

The red-legged partridge (Alectoris rufa) is the most important gamebird in Spain. Due to population declines in recent decades, management approaches increasingly include the release of farm-reared partridges and the establishment of so-called intensive estates, where hunting is based on put-and-take partridges. The release of farm-reared partridges is controversial because these birds negatively affect wild populations. However, according to managers, releases are necessary to maintain commercial hunting. We analysed economic parameters using data provided by 20 red-legged partridge hunting estates with different management and economic aims in central Spain. We calculated total revenues, total expenses, benefits and profitability of these estates and simulated results under two different scenarios (prices for buying farm-reared partridges being 15 % higher and prices for hunting in estates not using releases being 15 % higher) attempting to mimic the internalization of some ecological costs of farm-reared birds or possible rewards from using wild populations sustainably. Non-commercial estates (n = 5), as expected, just broke even, with almost no benefits. Benefits of intensive estates, where massive releases throughout the hunting season allow a much higher harvest, were on average an order of magnitude higher (20,404 ± 24,413 €/km, n = 8) than those of other commercial estates (1713 ± 1280 €/km, n = 7). Benefits of non-intensive commercial estates using releases were on average lower than those of commercial estates without releases. In fact, profitability of non-intensive commercial estates not using releases was similar to that of intensive estates. Any of the two price scenarios considered led to non-intensive commercial estates not using releases being the most profitable on average. Thus, efforts should be made to identify ways of improving economic profitability of non-intensive estates, which may be important for promoting hunting management styles that are ecologically more beneficial., Work was supported by the European Commission (7th Framework Programme for R&D through project HUNT, 212160, FP7-ENV-2007-1), JCCM through project ‘Efecto del medio natural, las prácticas agrícolas, ganaderas y de gestión cinegética sobre las poblaciones de caza menor en los cotos pertenecientes a la Asociación de cotos de caza Sierra de Alcaraz Campo de Montiel’, and by CSIC (PIE 201330E105). S. Díaz Fernández had a predoctoral grant funded by the European Social Fund (ESF) and by JCCM (Operational Programme PRINCET 2005-2010). M. Delibes-Mateos is supported by the V Plan Propio de Investigación of the University of Seville.

BACKGROUND: Ecologically based rodent pest management using biological control has never been evaluated for vole plagues in Europe, although it has been successfully tested in other systems. The authors report on the first large-scale replicated experiment to study the usefulness of nest-box installation for increasing the breeding density of common kestrels (Falco tinnunculus) and barn owls (Tyto alba) as a potential biological control of common vole (Microtus arvalis) abundance in agricultural habitats in north-western Spain. RESULTS: The results show that: (1) population density of both predator species increased in response to both nest-site availability and vole density; (2) voles are a major prey for the common kestrels during the breeding period; (3) vole density during the increase phase of a population cycle may be reduced in crop fields near nest boxes. CONCLUSION: The installation of nest boxes provides nesting sites for barn owls and kestrels. Kestrel populations increased faster than in areas without artificial nests, and the common vole was one of their main prey during the breeding season. The results suggest that local (field) effects could be found in terms of reduced vole density. If so, this could be an environmentally friendly and cheap vole control technique to be considered on a larger scale. © 2012 Society of Chemical Industry

Hyperpredation can be described as a restrictive case of apparent competition where an increased number of primary prey species indirectly induces the decrease of the secondary prey species through numerical response of predators to the primary prey dynamics. It has been proposed that rabbit hemorrhagic disease (RHD), which decimated populations of European wild rabbit (Oryctolagus cuniculus) in Spain, led to prey switching by raptors towards red-legged partridges (Alectoris rufa) causing declines in their populations as a peculiar case of hyperpredation. We have reviewed field studies that disagree with estimates (based on bag records) of recent increases of rabbit and partridge numbers in Spain. Because of an increase in releases of farm-reared animals, there is doubt about the use of bag records to accurately estimate population trends in recent decades. We also provide new data and discuss some analytical considerations related to the temporal and spatial scales that might affect the interpretation of data. Finally, we discuss why studies associated with raptor food habits, predator population dynamics and predator distribution suggest that diet data are not sufficient to link patterns and processes. Although we agree that the RHD outbreak has markedly affected rabbit populations, which has indirectly affected many other species in the Iberian Peninsula, we consider that hyperpredation mediated by raptors has not been clearly demonstrated. In contrast, endorsing the hypothesis of raptor-mediated hyperpredation without sufficient proof may have conflictive consequences if we consider the increased persecution of raptors in recent decades in Spain., J.A. Blanco-Aguiar was supported by Fundação para a Ciência e a Tecnologia (SFRH/BPD/65464/2009) grant. M. Delibes-Mateos was supported by a Juan de la Cierva research contract awarded by the Ministerio de Ciencia e Innovación—Fondo European Social Fund. F. Casas was supported by a postdoctoral grant of the Junta de Comunidades de Castilla la Mancha (JCCM).

The onset of incubation before the end of laying imposes asynchrony at hatching and, therefore, a size hierarchy in the brood. It has been argued that hatching asynchrony might be a strategy to improve reproductive output in terms of quality or quantity of offspring. However, little is known about the mediating effect of hatching asynchrony on offspring quality when brood reduction occurs. Here, we investigate the relationship between phenotypic quality and hatching asynchrony in Common Kestrel Falco tinnunculus nestlings in Spain. Hatching asynchrony did not increase breeding success or nestling quality. Furthermore, hatching asynchrony and brood reduction had different effects on nestlings’ phytohaematogglutinin (PHA)-mediated immune response and nestling growth. In asynchronous and reduced broods (in which at least one nestling died), nestlings showed a stronger PHA-mediated immune response and tended to have a smaller body size compared with nestlings raised in synchronous and reduced broods. When brood reduction occurred in broods hatched synchronously, there was no effect on nestling size, but nestlings had a relatively poor PHA-mediated immune response compared with nestlings raised in asynchronous and reduced broods. We suggest that resources for growth can be directed to immune function only in asynchronously hatched broods, resulting in improved nestling quality, as suggested by their immune response. We also found that males produced a greater PHA-mediated immune response than females only in brood-reduced nests without any effect on nestling size or condition, suggesting that females may trade off immune activities and body condition, size or weight. Overall, our results suggest that hatching pattern and brood reduction may mediate resource allocation to different fitness traits. They also highlight that the resolution of immune-related trade-offs when brood reduction occurs may differ between male and female nestlings.

We tested some predictions of parental investment theory by studying the aggressive behaviour of colonial nesting chinstrap penguins (Pygoscelis antarctica) against human intruders into their nesting territories. We tested for differences in the aggressive behaviour of penguins according to offspring age (eggs vs. chicks), offspring number, nest location in the colonies (central vs. peripheral) and sex. Offspring age was the main factor influencing nest defence, although nest location and sex were also important. Chicks were defended more strongly than eggs, in accordance with changes in the reproductive value of offspring, and this increase in aggressiveness was not related to revisitation of the same individuals. The level of aggression of penguins breeding in central sites was higher than that of peripheral birds, a difference that could be due to the lower residual reproductive value of central-nesting, probably older, birds. The stronger aggressiveness of males could be due to a combination of factors related to sexual selection and life-history traits. Offspring number did not affect the level of nest defence.

Positive interactions between species can have important conservation implications, especially when the species associating are both vulnerable. We studied the habitat use of pin-tailed sandgrouses Pterocles alchata and their association with another vulnerable species, the little bustard Tetrax tetrax in agrarian pseudosteppes of central Spain using radio-tracking. The occurrence of mixed-species flocks varied seasonally, being more frequent in winter (65% of pin-tailed sandgrouse flocks). In this season, pin-tailed sandgrouses preferred stubble fields and fallows. Moreover, we found that habitat selection of pin-tailed sandgrouse depended on the association with little bustards in mixed-species flocks. When in mixed-species groups, sandgrouses changed their agrarian substrate preferences, and used stubble fields significantly more often than when in sandgrouse-only flocks. We also provide evidence that pin-tailed sandgrouse benefited from the anti-predator vigilance of little bustards, allowing sandgrouse to exploit new feeding grounds (stubble fields) that would otherwise be too risky to exploit. Our results indicate a close positive association between these two species, which are both declining in Europe, and we discuss implications for their management and conservation. We also recommend taking into account inter-specific positive interactions when designing conservation strategies for threatened species.

Oxidative stress is the imbalance between the production of pro‐oxidant substances and the level of antioxidant defenses, which leads to oxidative damage. It has been proposed that senescence is the result of accumulated oxidative damage throughout life. In birds, the sources of individual variability in oxidative stress are still poorly understood. Among these sources, age, as related to senescence, should be particularly relevant. Furthermore, recent findings suggest that breeding effort may also deeply influence susceptibility to oxidative stress. However, there is still no evidence of a link between breeding effort and oxidative damage in any vertebrate. Here we analyzed 288 captive red‐legged partridges (Alectoris rufa) across a wide age range (i.e., 1–8 yr old), thus including potentially senescent birds. In spite of limitations due to the cross‐sectional approach, results revealed that old birds produced less offspring and endured higher levels of oxidized glutathione and peroxidized lipids in erythrocytes than did middle‐aged individuals. Old birds also showed higher plasma total antioxidant status and uric acid levels than did younger birds, but lower amounts of circulating carotenoids. Furthermore, hatching success was negatively correlated to lipid peroxidation in females but not in males, supporting the hypothesis that breeding effort promotes oxidative damage., C.A.‐A. and L.P.‐R. were funded by a Ramon y Cajal Fellowship and a predoctoral Formación del Profesorado Universitario grant, respectively (Ministerio de Educación y Ciencia, Spain). The study was funded by Junta de Comunidades de Castilla–La Mancha (project PAI‐06‐0018) and Ministerio de Educación y Ciencia (project CGL2006‐10357‐C02‐02), both from Spain.

Double-nesting behaviour, a rare breeding system in which females lay in two nests, one incubated by herself and the other one by her mate, could be considered an intermediate stage in the evolutionary trend from biparental to uniparental care of single clutches. We examined the occurrence and success of double-nesting behaviour in Red-legged Partridges Alectoris rufa in Central Spain. Clutch size and hatching success were recorded, as well as the variation in these between years and between incubating sexes. Participation in incubation was higher for females (94.76%) than males (41.0%), and the proportion of incubating males varied markedly between years, with no incubating males in one dry year and approximately 50% of males incubating in other years. There was significant variation among years and between sexes in laying date, clutch size and hatching success. Clutch size decreased with later laying date in males and females. The probability of clutch loss to predation differed between sexes, being much higher for nests incubated by females. Our results suggest that both rainfall and predation influence the occurrence and success of double-nesting.

Hunting is one of the human activities that directly affect wildlife and has received increasing attention given its socioeconomic dimensions. Most studies have been conducted on coastal and wetland areas and showed that hunting activity can greatly affect bird behaviour and distribution. Hunting-free reserves for game species are zones where birds find an area of reduced disturbance. We evaluated the effect of hunting activities on the behaviour and use of hunting-free areas of lapwings Vanellus vanellus, golden plovers Pluvialis apricaria and little bustards Tetrax tetrax in agricultural areas. We compared the habitat use and behaviour of birds on days before, during and after hunting took place. All three studied species showed strong behavioural responses to hunting activities. Hunting activity increased flight probability and time spent vigilant (higher on hunting days than just before and after a hunting day), to the detriment of resting. We also found distributional (use of hunting-free reserve) responses to hunting activities, with hunting-free reserves being used more frequently during hunting days. Thus, reserves can mitigate the disturbance caused by hunting activities, benefiting threatened species in agricultural areas. Increasing the size or number of hunting-free areas might be an important management and conservation tool to reduce the impacts of hunting activities., F.C. was supported by a Marie Curie fellowship of the European Community programme. F.M. was supported by a NERC advanced fellowship, and a grant from the Junta de Comunidades de Castilla-la-Mancha, Spain (PAI06-0112).

An analysis of the orientation of 182 nest sites of the Black Kite Milvus migrans in two areas in south and central Spain found that orientations toward the east were preferred. In southern Spain an analysis of the relationship between nest orientation and hatching success showed that success was lower among the nests located in non-preferred orientations, with some inter-annual variation. The tendency to orientate nests toward the east was greater among the early nesting pairs and the effect that the orientation had on the hatching success was also greater than in late nesting pairs. The data suggest that rainfall and prevailing winds were the main factors conditioning nest orientation.

Human recreational activities are becoming increasingly widespread and frequent, a fact that may potentially exacerbate their effects on wildlife. These human-related disturbances on animals may induce behavioural and physiological changes that can ultimately affect their fitness, showing a similar anti-predator response that against natural predator or other threats. Here, we combine the use of behavioural and physiological approaches to assess the potential effect of winter human activities on a threatened farmland bird in Europe, the pin-tailed sandgrouse (Pterocles alchata). We compared before, during and after weekend variations in human activity rates, pin-tailed sandgrouse behaviour (flocking and flying behaviour, interspecific association in mixed flocks and habitat use) and faecal glucocorticoid metabolite concentrations. Human disturbances, in particular those associated with hunting activities, peaked during weekends. Sandgrouse showed significant behavioural changes (increased sandgrouse-only flock sizes, increased proportion of birds flying and changes in habitat use) during weekends and higher faecal glucocorticoid metabolite concentrations after the weekends compared with during or before weekends. Therefore, physiological stress levels could be modulated by behavioural adjustments such as increased flock sizes and changes in habitat use that may allow sandgrouse to cope with increased human disturbance rates during weekends. Nevertheless, temporal and spatial organization of hunting days among groups of estates might be good strategies to buffer these potential adverse effects on wintering pin-tailed sandgrouse and other steppe species of conservation concern, while preserving a socio-economically important activity such as hunting., This study is a contribution to projects funded by the Dirección General de Investigación (projects CGL2007-429 66322/BOS and CGL2008-04282/BOS), Consejería de Educación y Ciencia de Castilla-La Mancha (projects PAI08-0171-9582 and PAC06-137), Comunidad de Madrid and Universidad Autónoma de Madrid (CCG10-UAM/AMB-5325), Spanish Ministry of Science (CGL2008-04282/BOS and CGL2009-13029/BOS) and REMEDINAL2 network of the CAM (S-2009/AMB/1783). FC was supported by the Andalucía Talent Hub Program launched by the Andalusian Knowledge Agency, cofounded by the European Union’s Seventh Framework Program, Marie Skłodowska-Curie actions (COFUND–Grant Agreement n° 291780) and the Ministry of Economy, Innovation, Science and Employment of the Junta de Andalucía, and a JAE-Doc contract funded by CSIC and the European Social Fund (ESF). ABL was supported by the CGL2008-04282/BOS project and by the 2012-BIN-4462 research grant conceded by the UCLM and RT by a PhD grant from the Spanish Ministry of Education (FPU-grant no. AP2009-0762).

Wild red-legged partridge populations have experienced important declines in recent decades. With an aim to increase or maintain hunting quotas, releases of farm-reared red-legged partridges have concomitantly increased. However, the sustainability of this management practice is increasingly questioned. Farm-reared partridges suffer a high mortality rate immediately after release, and many released birds may already be dead before hunting takes place. Therefore, it is possible that if hunters adjust harvest to the number of farm-reared released birds, this may lead to an overhunting of the wild breeding stocks. We investigated here whether autumn mortality by hunting of radio-tracked birds that bred in the previous summer differed between hunting estates that use or do not use releases as part of their management practices. Although our sample size was limited (32 radio-tagged birds monitored throughout the hunting season in four estates, with only one conducting releases), our results report novel data that support this cause for concern. We found that hunting was the main cause of mortality and that the proportion of hunted partridges was much higher in the estate with releases of farm-reared birds than in the three estates that did not use releases. Therefore, the release of farm-reared partridges, instead of reducing hunting pressure on the breeding stock through a potential dilution effect, may have an opposite effect. This should be confirmed with more spatial replicates, but raises serious concerns regarding the long term sustainability of wild partridge populations and their exploitation for hunting purposes in estates that overhunt partridge populations due to releases., This study was supported by the Comunidad de Castilla-La Mancha (Bases científicas preliminares para un plan de conservación de la perdiz roja en Castilla-La Mancha) and Spanish Ministry of Science (MCYT-REN200307851/GLO and CGL2004-02568/BOS). FC was supported by the Andalucía Talent Hub Program launched by the Andalusian Knowledge Agency, cofounded by the European Union’s Seventh Framework Program, Marie Skłodowska-Curie actions (COFUND–Grant Agreement n° 291780) and the Ministry of Economy, Innovation, Science and Employment of the Junta de Andalucía.

We studied the helminth community and body condition of 99 hunter-harvested red-legged partridges (Alectoris rufa) from Ciudad Real (Central Spain). Forty-six were sampled in two game estates where an important number of farm-reared red-legged partridges are released yearly. The remaining 53 were obtained from natural wild populations adjacent to one of the estates with releases. Four nematode species (Heterakis gallinarum, Aonchoteca caudinflata, Eucoleus contortus and Cheilospirura gruveli) and two cestode species (Raillietina (R.) tetragona and Skryabinia bolivari) were identified. The managed areas showed higher parasite diversity, with higher prevalences and intensities for all helminths found. Three of these species were typical of farm-bred partridges and two of these, A. caundinflata and S. bolivari, were found parasitizing adult partridges. This suggests introduction of these helminths into the breeding population of managed states. The birds sampled in the nonmanaged estates showed a better body condition, but no relation with parasite infection was found. Our results suggest that the release of farm-reared red-legged partridges, a strategy that is becoming a common practice in Spanish hunting areas, poses risk to wild populations because of introducing parasites. However, these results also suggest that simply stopping releases may be a good way to remove locally those parasites from populations, as the establishment of the introduced parasites seems limited., This is a contribution to the joint project CSIC/Principado de Asturias and to CYCIT projects MCYT-REN200307851/GLO and CGL2004-02568/BOS. Lorenzo Pérez-Rodríguez had a FPU grant from the Spanish Ministerio de Educación y Ciencia and Fabián Casas from Junta de Comunidades de Castilla-La Mancha.

Knowledge about how hunting pressure is determined, and the relative efficacy of different mechanisms to regulate harvest, can help to improve the managers’ decision-making process. We developed a general framework about the decision-making process that regulates red-legged partridge (Alectoris rufa) hunting pressure in central Spain based on information from a focus group and individual interviews with game managers. We also used available information to compare the efficiency of different tools thus improving some decision steps. We evaluated the cost-effectiveness of different population monitoring methods as a way to reduce uncertainty on partridge availability to hunters. Additionally, we investigated the relationship between annual harvest and various regulatory mechanisms of partridge hunting pressure used in the study area to identify the most potentially useful one to limit annual take-off. Game managers usually set hunting pressure after a qualitative assessment on population abundance prior to the hunting season, but this decision was frequently modified during the course of the hunting season according to variations in catch or perceived abundance at that time. Our results showed that kilometric abundance indices (counting partridges from cars along line transects) was a simple cost-efficient and reliable estimate of partridge density (estimated by Distance sampling). A variety of regulatory mechanisms were used by managers. The variables that most affected annual harvest (in addition to partridge abundance) were the number of driven-shooting days, and hunter density in walked-up hunting days, suggesting that their adjustment will be the most efficient regulatory mechanisms. We conclude that adequate monitoring on population abundance should be a critical step for managers’ decision-making, and that a better understanding of the relative value of regulatory mechanisms, combining social and ecological approaches, would help improving our understanding of any human-mediated system, thus leading to better management recommendations., Work was supported by the European Commission (7th Framework Programme for R&D through project HUNT, 212160, FP7-ENV-2007-1); Consejería de Agricultura of JCCM; by the Ministerio de Ciencia y Tecnología (CGL2008-04282/BOS), and by CSIC (PIE 201330E105).

Whether predators can limit their prey has been a topic of scientific debate for decades. Traditionally it was believed that predators take only wounded, sick, old or otherwise low-quality individuals, and thus have little impact on prey populations. However, there is increasing evidence that, at least under certain circumstances, vertebrate predators may indeed limit prey numbers. This potential role of predators as limiting factors of prey populations has created conflicts between predators and human hunters, because the hunters may see predators as competitors for the same resources. A particularly acute conflict has emerged over the past few decades between gamebird hunters and birds of prey in Europe. As a part of a European-wide research project, we reviewed literature on the relationships between birds of prey and gamebirds. We start by analysing available data on the diets of 52 European raptor and owl species. There are some 32 species, mostly specialist predators feeding on small mammals, small passerine birds or insects, which never or very rarely include game animals (e.g. hares, rabbits, gamebirds) in their diet. A second group (20 species) consists of medium-sized and large raptors which prey on game, but for which the proportion in the diet varies temporally and spatially. Only three raptor species can have rather large proportions of gamebirds in their diet, and another seven species may utilise gamebirds locally to a great extent. We point out that the percentage of a given prey species in the diet of an avian predator does not necessarily reflect the impact of that predator on densities of prey populations. Next, we summarise available data on the numerical responses of avian predators to changing gamebird numbers. In half of these studies, no numerical response was found, while in the remainder a response was detected such that either raptor density or breeding success increased with density of gamebirds. Data on the functional responses of raptors were scarce. Most studies of the interaction between raptors and gamebird populations give some estimate of the predation rate (per cent of prey population taken by predator), but less often do they evaluate the subsequent reduction in the pre-harvest population or the potential limiting effect on breeding numbers. The few existing studies indicate that, under certain conditions, raptor predation may limit gamebird populations and reduce gamebird harvests. However, the number and extent of such studies are too modest to draw firm conclusions. Furthermore, their geographical bias to northern Europe, where predator–prey communities are typically simpler than in the south, precludes extrapolation to more diverse southern European ecosystems. There is an urgent need to develop further studies, particularly in southern Europe, to determine the functional and numerical responses of raptors to gamebird populations in species and environments other than those already evaluated in existing studies. Furthermore, additional field experiments are needed in which raptor and possibly also mammalian predator numbers are manipulated on a sufficiently large spatial and temporal scale. Other aspects that have been little studied are the role of predation by the non-breeding part of the raptor population, or floaters, on the breeding success and survival of gamebirds, as well as the effect of intra-guild predation. Finally there is a need for further research on practical methods to reduce raptor predation on gamebirds and thus reduce conflict between raptor conservation and gamebird management., The work was financially supported by the EuropeanCommission, and is part of project REGHAB (ReconcilingGamebird Hunting and Biodiversity; contract no.EVK2-CT-2000-200004).

Parental favoritism in birds would be enhanced if parents can control any egg feature influencing the ontogeny of the embryo during incubation. Egg size and composition may influence the duration of incubation and hatching periods, and eggs bearing embryos of different sex may differ in size and composition. Therefore, the sex of the embryo could also influence its ontogeny before hatching. We tested this prediction by investigating the duration of the embryonic period of different-sex embryos in the Eurasian kestrel (Falco tinnunculus), a sexually dimorphic raptor in which adult females are approximately 20% heavier than are adult males. We found the first evidence of sex differences in the duration of the embryonic period in avian eggs. Female embryos had a shorter embryonic period than did male embryos, which allowed females to hatch earlier in the hatching sequence and assume a higher rank than that of males in the intrabrood size hierarchy. Embryos with a fast growth and development resulted in hatchlings with greater residual reserves and thus larger mass, which suggests that a shorter embryonic period requires less maintenance metabolism relative to growth. Our results also indicated that early hatching may be advantageous to gain a high rank in the size hierarchy within the brood independently of the effect of sex on fledgling mass. Sex differences in avian egg ontogeny may therefore be a factor shaping life-history traits associated with parental control of sibling competition, which should be addressed in any future work on optimal reproductive investment.

Capturing and marking free-living birds permits the study of important aspects of their biology but may have undesirable effects. Bird welfare should be a primary concern, so it is necessary to evaluate and minimize any adverse effects of procedures used. We assess short-term effects associated with the capture, handling and tagging with backpack-mounted transmitters of Pin-tailed Pterocles alchata and Black-bellied Pterocles orientalis Sandgrouse, steppe birds of conservation concern. There was a significantly higher mortality (15%) during the first week after capture than during the following weeks (, F. Casas was supported by a JAE-Doc contract funded by CSIC and the European Social Fund (ESF) and by the Steppe-Ahead project funded by FGCSIC. Funding came from the Dirección General de Investigación (projects CGL2007-66322/BOS and CGL2008-04282/BOS), Consejería de Educación y Ciencia de Castilla-La Mancha (projects PAI08-0171-9582 and PAC06-137) and Bardenas Reales Biosphere Reserve (projects UCTR09-0268, UCTR110053 and UCTR120308).

The reduction of game and fish populations has increased investment in management practices. Hunting and fishing managers use several tools to maximize harvest. Managers need to know the impact their management has on wild populations. This issue is especially important to improve management efficacy and biodiversity conservation. We used questionnaires and field bird surveys in 48 hunting estates to assess whether red-legged partridge Alectoris rufa young/ adult ratio and summer abundance were related to the intensity of management (provision of supplementary food and water, predator control and releases of farm-bred partridges), harvest intensity or habitat in Central Spain. We hypothesized that partridge abundance would be higher where management practices were applied more intensively. Variation in young/ adult ratio among estates was best explained by habitat, year and some management practices. Density of feeders and water points had a positive relationship with this ratio, while the density of partridges released and magpies controlled were negatively related to it. The variables with greatest relative importance were feeders, releases and year. Variations in postbreeding red-legged partridge abundance among estates were best explained by habitat, year, the same management variables that influenced young/adult ratio, and harvest intensity. Harvest intensity was negatively related to partridge abundance. The other management variables had the same type of relationship with abundance as with young/adult ratio, except magpie control. Variables with greatest relative importance were habitat, feeders, water points, releases and harvest intensity. Our study suggests that management had an overall important effect on post-breeding partridge abundance. However, this effect varied among tools, as some had the desired effect (increase in partridge abundance), whereas others did not or even had a negative relationship (such as release of farm-reared birds) and can be thus considered inefficient or even detrimental. We advise reconsidering their use from both ecological and economical points of view., This work was supported by the European Commission under the 7th Framework Programme for RTD through project HUNT (212160, FP7-ENV-2007- 1), the Consejería de Agricultura of JCCM through project ‘‘Efecto del medio natural, las prácticas agrícolas, ganaderas y de gestión cinegética sobre las poblaciones de caza menor en los cotos pertenecientes a la Asociación de cotos de caza Sierra de Alcaraz-Campo de Montiel’’, and the Ministerio de Ciencia y Tecnología (CGL2008-04282/BOS). S. Díaz-Fernández had a predoctoral grant funded by the European Social Fund (ESF) and by JCCM (Operational Programme PRINCET 2005-2010). F. Casas was supported by a JAE-Doc contract funded by the ESF. Currently, M. Martinez-Haro is supported by a postdoctoral grant (Ref: SFRH/BPD/73890/2010) funded by the Portuguese Foundation for Science and Technology (FCT), the ESF and POPH programme.

We investigated possible pre-hatching mechanisms of sex-differential investment by females that may contribute to offspring sex-ratio adjustment enhancing the fitness return from reproductive effort in the spotless starling (Sturnus unicolor). We found a seasonal shift in sex ratio from daughters to sons as the season advances. Furthermore, the probability of breeding at 1-year old and recruitment into the breeding population in daughters is associated with laying date but not with mass at fledging. The reverse is true for males which rarely bred at 1-year old. We also found that eggs containing female embryos are significantly heavier than those containing males in spite of the slight sexual dimorphism in favour of males. This suggests maternal control of provisioning, favouring daughters that may balance sibling mortality and competition with their brothers. Our results on seasonal variation in sex ratio and differential egg provisioning are consistent with an adaptive tactic in which mothers increase their reproductive return by enhancing the probability that daughters survive and breed in their first year of life.

At least 19 hypotheses have been proposed to explain the evolutionary significance of avian hatching asynchrony, and hatching patterns have been suggested to be the result of several simultaneous selective pressures. Hatching asynchrony was experimentally modified in the black kite Milvus migrans by manipulating the onset of incubation during the laying period. Delayed onset of incubation reduced egg viability of first-laid eggs, especially when ambient temperature during the laying period was high. Brood reduction (nestling mortality by starvation or siblicide) was more commonly observed in asynchronous nests. The growth rate was slower in synchronous broods, probably due to stronger sibling rivalry in broods with high size symmetry. Last-hatched chicks in synchronous broods fledged at a small size/mass, while in control broods, hatching order affected growth rates, but not final size. Brood reduction, variable growth rates, and the ability to face long periods of food scarcity are probably mechanisms to adjust productivity to stochastic food availability in a highly opportunistic predator. The natural pattern of hatching asynchrony may be the consequence of opposing selective forces. Extreme hatching synchrony is associated with slow growth rates, small final size of last-hatched chicks, and low viability of first-laid eggs, while extreme hatching asynchrony is associated with high mortality rates. Females seem to facultatively manipulate the degree of hatching asynchrony according to those pressures, because hatching asynchrony of control clutches was positively correlated with temperature during laying, and negatively correlated with the rate of rabbit consumption.

In siblicidal species, hatching asynchrony could act to reduce sibling rivalry or promote the death of last-hatched chicks. The pattern of hatching asynchrony was experimentally altered in the black kite Milvus migrans. Hatching asynchrony in control broods was intermediate between those of experimentally synchronised and asynchronised broods. Sibling aggression and wounds on the chicks were more commonly observed early in the nestling period and in synchronous nests. Serious injuries were observed on last-hatched chicks in asynchronous nests, as were observations of intimidated or crushed chicks. Sibling aggression was related to food abundance, but some chicks died at an early age in nests with abundant food (cainism). Cainism was more commonly found in asynchronous nests. For species with facultative siblicide, moderate hatching asynchrony could be a compromise between reducing sibling rivalry and avoiding large size differences between sibs that would result in cainism. Female black kites preferentially fed the smallest chicks and exhibited behaviours to reduce sibling aggression, contrary to observations in other siblicidal species. In a highly opportunistic forager such as the black kite, a strategy may exist to protract the life of all the chicks in the brood, waiting for unpredictable situations of food overabundance. This would induce the appearance of a parent-offspring conflict over brood reduction, reflected in the existence of a possible anticipated response by some of the chicks (cainism) and in the appearance of special behaviours by the parents to selectively feed smaller chicks or reduce sibling aggression. In this facultatively siblicidal species, cainism does not seem to be the final stage of an evolutionary trend favouring the raising of high-quality chicks, but a manifestation of a parent-offspring conflict over brood size.

The European rabbit Oryctolagus cuniculus, an important game species in Spain, has declined sharply since the arrival of haemorrhagic disease in 1988. As a consequence of this decline, it appears that illegal and extensive persecution of predators has increased. We have assessed the impact of this persecution on red kites Milvus milvus. Around 90% of the populations studied have declined during the last 3–10 years, and the species' range has been reduced since 1980, particularly in high rabbit density areas (those most valuable for hunters). Currently, stable or increasing populations of red kites are located in areas of low rabbit density. Their abundance in areas of high rabbit density is similar to that recorded during the 1970s, when, after the spread of myxomatosis over Spain, government-sponsored campaigns of vermin extermination were carried out. Although red kites cannot be considered important predators of rabbits, they are disproportionally suffering the effects of human persecution, because of their susceptibility to shooting and poisoning, and a lack of understanding among hunters. We discuss the management strategies that might be used during population crashes of game species to avoid unjustified persecution of predators.

Sandgrouse are birds of arid environments adapted to cope with extreme temperature variations. We used temperature data-loggers to remotely study incubation rhythms by pin-tailed and black-bellied sandgrouse in Spain. In both species, mates switched incubation roles twice a day, between 08:00 and 10:00 and between 19:30 and 21:30, when the nest and ambient temperature were most similar. During mate switches, sandgrouse preferred to risk a cooling rather than a warming of eggs. In the pin-tailed sandgrouse, the timing of morning switches was consistent within-pairs, while the timing of evening switches was more related to sunset time. Absences lasted longer following a disturbance than during a mate switch. During disturbances, changes in nest temperatures depended on the changes in outside temperature, and negatively correlated with absence duration. Absences following a disturbance were shorter when the outside temperature was higher. Nesting success was low (19%), with no noticeable effect of data-loggers. Our study highlights some of the constraints that birds breeding in arid environments, such as sandgrouse, face during incubation. It also stresses out the importance of evaluating the consequences of disturbances during incubation, in particular nest visits. Temperature data-loggers can provide an easy and effective way of monitoring nests, without the need of repeated nest visits., This study was funded by the Spanish “Ministerio de Educacion y Ciencia” (project CGL2008-04282/BOS and intramural GranGanga grant to FM) and the “Comunidad de las Bardenas Reales de Navarra” (project UCTR110053). FC was supported by a JAE-Doc grant (“Junta para la Ampliación de Estudios”, European Social Fund). This study also contributes to Steppe-Ahead, a project funded by the FGCSIC.

Rodent outbreaks cause significant crop damages in agricultural areas worldwide, but routinely monitoring large areas at low cost remains a challenge. The common vole Microtus arvalis has recently colonized the agricultural plains of the northern Iberian Plateau, an area where it has started to produce population outbreaks with important impacts in agriculture, the environment and human health. Vole monitoring has become of prime importance to implement preventive management measures to control populations. In order to find a simple and reliable vole monitoring method to be applied in large areas, we compared abundance estimates derived from three methods: capture-mark-recapture (CMR), single capture events (SCE) and presence/absence of vole activity signs (VAS) during three seasons and on the main agricultural habitats in the study area. We show that an activity index based on the presence of fresh droppings and/or clippings had a similar performance to SCE in a large sample of plots (n = 222) across habitats and seasons. Data obtained with both methods (SCE, VAS) were also well correlated with those obtained with CMR, despite a limited sample size (n = 23 CMR plots). We suggest that the VAS method, which is a cheaper and easier alternative to trapping methods, provides a promising tool for scientists and managers to implement large scale monitoring of common vole in agricultural areas., Funding was from the ECOCYCLES project (BIODIVERSA. ERA-net project, European Union's 6th Framework Programme for Research); PhD grant JAE-Predoc, from the CSIC, jointly funded by the European Social Fund to D.J. This study also contributes to the projects ECOVOLE (CGL2012-35348) and TOPILLAZO (CGL2011-30274/BOS) funded by the Ministerio de Economia y Competitividad of Spain.

We evaluated the effect of conspecific abundance and habitat quality of leks on the territorial behaviour of males in an exploded lekking species, the Little Bustard (Tetrax tetrax). The hypothesis that males more intensely defend territories with higher conspecific abundance and better habitat quality was evaluated experimentally analysing the agonistic response of experimental males to male decoys placed on their displaying areas. Decoy experiments showed that the intensity of display territory defence by little bustard males is density dependent. The time experimental males took to return to their display sites after decoy placement decreased with abundance of both males and females. The strength of their final response was positively associated to local male and female abundance in the vicinity of their display sites. Habitat quality also influenced males' display territory defence since the intensity of male response increased with the degree of natural vegetation cover. Habitat quality was particularly relevant in explaining variation of experimental males' snort call rate, which decreased with the degree in plough cover and increased with the number of fields in the lekking area. Snort call rate decreased with the level of male aggregation and was lowest in males exhibiting the strongest aggressive response to decoys. These results add new evidence for the density dependence of species' breeding territorial behaviour, supporting density-dependent models of lek formation and reinforcing the role of resources defence in exploded lek mating systems., FC and JM-P were supported by a JAE-Doc contract funded by Spanish Research Council and the European Social Fund (ESF), and ELG was funded by a FPU grant from the Spanish Ministry of Education. This paper contributes to projects CGL2004-06147-C02-01, CGL2004-06147-C02-02 and CGL2009-13029/BOS of the Spanish Ministry of Science, as well as to the REMEDINAL2 network of the Community of Madrid (S-2009/AMB/1783).

Ascertaining which niche processes allow coexistence between closely related species is of special interest in ecology. We quantified variations in the environmental niches and densities of two congeneric species, the pin-tailed and the black-bellied sandgrouse (Pterocles alchata and Pterocles orientalis) in allopatry and sympatry under similar abiotic, habitat and dispersal contexts to understand their coexistence. Using principal component analysis, we defined environmental gradients (niche dimensions) including abiotic, habitat and anthropogenic variables, and calculated niche breadth, position and overlap of both species in sympatry and allopatry. Additionally, sandgrouse density was modelled as a function of the niche dimensions and the density of the other species. We found evidence that each species occupies distinct environmental niches in sympatry and in allopatry. The black-bellied sandgrouse exploits a broader range of environmental conditions (wider niche breadth) while the pin-tailed sandgrouse reaches high densities where conditions seem to match its optimum. In sympatry, both species shift their niches to intermediate positions, indicating the importance of abiotic factors in setting coexistence areas. Environmental conditions determine regional densities of pin-tailed sandgrouse whereas biotic interactions explain the density of the black-bellied sandgrouse in areas with abiotic conditions similarly conducive for both species. Highly suitable areas for the pin-tailed sandgrouse fall beyond the upper thermal limit of the black-bellied sandgrouse, leading to niche segregation and low densities for the latter. Finally, local niche shift and expansion plus possible heterospecific aggregation allow the pin-tailed sandgrouse to thrive in a priori less favourable environments. This work provides insight into how different mechanisms allow species coexistence and how species densities vary in sympatry compared to allopatry as a result of environmental filtering and biotic interactions., Financial support was provided by the Dirección General de Investigación (project CGL2008-04282/BOS) and the HNV project (Spanish Ministry of Rural and Marine Environment). A. Benítez-López was supported by the 2012-BIN-4462 research grant awarded by the Universidad de Castilla-La Mancha.

Knowledge of the factors determining species distributions is essential for developing conservation strategies. SandgrousePterocles alchata andP. orientalis are threatened in Spain, the stronghold of European populations. Spatial modelling was used to: (1) assess the relative importance of abiotic, anthropogenic and geographical factors in the distribution of both sandgrouse species, (2) determine the most important anthropogenic predictors for each species occurrence, and (3) identify areas where conservation efforts should be prioritized. Abiotic and anthropogenic factors explained most of the variation in sandgrouse distributions. Both species were associated with arid flatlands, arable land cover being the most important anthropogenic variable determining their distribution. The Common Agricultural Policy (CAP) is the main driver of agricultural management in Europe, and may thus have a direct effect on sandgrouse distributions. P. orientalis exhibited broader habitat tolerance than P. alchata; the latter species tolerates warmer climates. Consequently, the network of core and marginally suitable areas identified for each species differs, and connectivity between the populations of these areas seems unlikely. Potential future changes in sandgrouse distribution will probably be directed principally by the synergistic effects of climate change and expected land-use transformations resulting from the new CAP and ongoing population growth, urbanization and infrastructure development., This research was jointly funded by the Dirección General de Investigación (project CGL2008–04282/BOS) and HNV project (MARM).

The reliability of road transects as a census method for wintering and breeding Red Kites was studied in Spain. Road transect data were compared with censuses of wintering populations made by roost counts and of breeding populations made by a combination of nest searching and detection of territorial pairs. The variation in population density explained a high percentage of the variance of abundance indices provided by road transects during winter (> 90%) and breeding seasons (85%). The estimation of densities from distances to the transect did not provide more accurate results than unadjusted counts. On the contrary, strip counts may consistently bias population estimates in species that are attracted by roads, or may provide unpredictably unrealistic results when the number of observations is low. Winter roost counts made in areas of high breeding density apparently underestimated the real populations, because resident Red Kites usually do not use roosts, and this was detected through the results obtaine...