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Migratory organisms can be vectors of parasitic host organisms that can then be transported along seasonal migratory journeys and spread across continents. Ornithophilic nidicolous ticks (e.g. soft ticks) include species responsible for the transmission of pathogens and bacteria, thus representing a health problem not only for wild species that are directly parasitized, but also for those that share the same environments or reproductive sites with them. In this regard, artificial nests for birds may turn out to be site-sources of parasites. Here, we document the occurrence of different life stages of Argas persicus ticks in nest boxes of wild birds in a natural area (not associated with poultry activities) of central coastal Italy (Maremma Regional Park, Tuscany). Between 2018 and 2022, 168 ticks were collected from nest boxes occupied by different secondary cavity-nesting birds, such as European rollers Coracias garrulus and scops owl Otus scops. Ticks were analysed morphologically, and selected specimens were also identified by mitochondrial ribosomal 16S (16S) subunit gene to ascertain their taxonomic status. All ticks were identified as Argas persicus. This finding not only suggests that this tick species has formed a viable population in this Italian region, but also further confirms the previously doubtful natural origin of the species at country level and sheds new light on its underestimated and little investigated distribution. Possible pathways of introduction and its potential impacts on local avian community are discussed.

Bird nests are specialized habitats because of their particular composition including nest detritus and bird droppings. In consequence, they attract a specialized arthropod community considered as nidicolous, which includes species only found in bird nests (strictly nidicolous) or sometimes found in bird nests (facultatively nidicolous). Because the factors influencing the entomofauna in bird nests are poorly understood, in autumn 2019, we collected nest material in 86 Barn Owl (Tyto alba) nest boxes. We investigated whether the invertebrate species richness was related to Barn Owl nest box occupancy, the density of available nest boxes and the landscape structure. We found 3,321 nidicolous beetle specimens belonging to 24 species. Species richness of strictly nidicolous beetles was 2.7 times higher in nest boxes occupied by a family of Barn Owls the previous spring compared to unoccupied nest boxes. It was also higher in sites that were more often occupied by Barn Owls in the five previous years and in areas surrounded by a higher proportion of crop fields. For facultatively nidicolous beetles, the density of Barn Owl nest boxes enhanced the species richness. In conclusion, our study suggests that the strictly nidicolous beetles benefit from occupied nest boxes of Barn Owls, whereas facultatively nidicolous beetles look for nest boxes independently of whether Barn Owls occupy them. Our study highlights the importance of bird nests for a suite of invertebrates.

Many studies have investigated how spring temperature affects laying dates and how this in turn affects the synchrony between nestling food demands and the insect food peak that follows tree budburst. While there is strong evidence that temperature itself acts as a cue for this plasticity in annual timing, the exact nature of the cue and response remains to be elucidated. Here we use long-term data on Great and Blue Tits and an unprecedented dataset on the location and phenology of 1396 trees to investigate whether small-scale variation in laying date can be explained by local tree phenology, and/or by tree species composition around nestboxes. Individual trees maintained their relative timing of budburst between years, while differences among tree species were more variable between springs. Contrary to expectation, we found no relation between first-egg dates and average budburst date at different distances around the nestbox. This can at least partly be explained by the very low degree of spatial autocorrelation in tree budburst. We did find an effect of local tree composition whereby Blue Tits, but not Great Tits, laid earlier in nestboxes surrounded by more oaks and fewer beeches. Although Blue Tit nest failure rate was higher in territories with more beech trees, independently of laying date, we found no evidence for preferential occupation of oak-dominated territories. Thus although we found some evidence for fine-scale effects of tree species on timing of breeding, the underlying mechanism remains unclear.

Urbanization has been shown to strongly affect community composition of various taxa with potentially strong shifts in ecological interactions, including those between hosts and parasites. We investigated the effect of urbanization on the composition of arthropods in nests of great tits in Flanders, Belgium. These nests contain taxonomically and functionally diverse arthropod communities including parasites, predators, detritivores and accidental commensals. Using a standardized hierarchical sampling design with subplots (200 m x 200 m) nested in plots (3 km x 3 km) of varying urbanization levels, we collected arthropods from nests of resident great tits after the young had fledged. Arthropods were extracted, identified to Primary Taxonomical Groups (PTG) and counted. Using generalized linear mixed models (GLMMs) we found diverging effects of urbanization on PTG occurrences and abundances at various levels, but we did not find an overall signal in arthropod diversity or richness. Also, visual inspection of non-metric multidimensional scaling (NMDS) plots did not reveal any community differences between urbanization levels at plot or subplot scales. Land use and environmental variables at different distances around nestboxes did not contribute much to the variation between communities. Our results indicate that arthropod nestbox communities are generally not adversely affected by urbanization, and even city gardens and parks harbor comparable communities to forests and suburban areas. We thus found no evidence for a parasite release effect due to urbanization, nor an increased risk of parasitism in human-dominated environments.

Anthropogenic disturbances induce stress in a variety of urban species. We examined the effects of traffic noise on the physiological stress response of nestling European Starlings (Sturnus vulgaris). Nest boxes were randomly assigned to either an experimental (increased urban noise played in nest box) or a control (typical urban/ambient noise) group. Heterophil/lymphocyte (H/L) ratios were determined to estimate physiological stress of nestlings at 11 and 15 days of age. Higher H/L ratios are associated with increased stress responses in birds. We predicted that nestlings in the experimental treatment would have higher H/L ratios and lower condition and fledging success than those in the control group on both days 11 and 15, but we detected no such differences on either day. Day 15 experimental nestlings, however, showed a non-significant trend toward lower H/L ratios than did day 15 control nestlings. We also examined whether nestlings became habituated (lower H/L ratios on day 15 than day 11) or sensitized (higher H/L ratios on day 15) to urban noise over time. There was a non-significant trend for experimental nestlings to have lower H/L ratios on day 15 than day 11, but no such pattern was detected in control nestlings. Our findings suggest that constant traffic noise is not stressful to nestlings in this urban-thriving species.

Interspecific or intraspecific destruction of eggs by other small bird species (Passeriformes) is a relatively rare behaviour. It is known from studies of several new world species from families Mimidae and Troglodytidae, but it has never been documented in the Eurasian wren (Troglodytes troglodytes). While studying the breeding biology of the white-throated dipper (Cinclus cinclus) in northern part of Central Slovakia, we documented seven events (frequency 1.8%) when Eurasian wren occupied a dipper’s nest during the breeding season. None of these breeding attempts by the dippers was successful. In all cases, the breeding pairs abandoned their nest. Except of these seven cases, we also found an abandoned nest (situated in the nest box under a bridge) with damaged eggs of the white-throated dipper. According to the intact nest bottom, we hypothesise that the nest was not predated. Here we probably describe the first case of egg destruction by the Eurasian wren in Europe.

Abstract Ecological factors and individual-specific traits affect parasite infestation in wild animals. Ixodid ticks are important ectoparasites of various vertebrate hosts, which include passerine bird species such as the great tit (Parus major). We studied various key ecological variables (breeding density, human disturbance) and phenotypic traits (exploratory behaviour, body condition) proposed to predict tick infestation probability and burden in great tits. Our study spanned 3 years and 12 nest box plots located in southern Germany. Breeding, adult great tits were assessed for exploration behaviour, body condition, and tick burden. Plots were open to human recreation; human disturbance was quantified in each plot as a recreation pressure index from biweekly nest box inspections. Infested individuals were repeatable in tick burden across years. These repeatable among-individual differences in tick burden were not attributable to exploration behaviour. However, faster explorers did have a higher infestation probability. Furthermore, body condition was negatively correlated to tick burden. Recreation pressure was correlated to increased infestation probability, although this relationship was just above the threshold of statistical significance. Our study implies that avian infestation probability and tick burden are each determined by distinct phenotypic traits and ecological factors. Our findings highlight the importance of animal behaviour and human disturbance in understanding variation in tick burden among avian hosts. Significance statement Various abiotic and biotic factors, including personality type, influence tick parasitism in birds, but exactly how all these factors interplay remains unclear. We studied a wild population of great tits over a 3-year period and assessed birds for their exploration behaviour and tick infestation. We found that more explorative great tits were more likely to be infested with ticks. By contrast, faster explorers did not have higher tick burdens. Tick burden was nevertheless moderately repeatable among individuals. Our results imply that animal personality influences the probability of parasite infestation, and that infestation likelihood versus intensity are determined by distinct mechanisms. Our work highlights the importance of animal behaviour to understand parasite infestation in wild populations.

The Blue Tit Cyanistes caeruleus prefer to use nest boxes to raise their young rather than nests in natural tree cavities. However, nest boxes provide a warm, humid microclimate that is favourable to the growth of rich bacterial communities. In this study we investigated how the bacterial community developed throughout the breeding season and whether it had any effect on egg or nestling mortality. Samples were collected across six sites and three breeding seasons at the completion of nest building, clutch completion and immediately post fledging. Bacterial counts were obtained for each sample, including a total bacterial count using non-selective media and bacterial counts on selective media for Staphylococcus spp. and Enterobacter spp, which may indicate pathogenicity to the birds. There were significantly more bacteria (total counts and counts for Staphylococcus spp. and Enterobacter spp. specifically) present within the nest box at the post fledging stage compared to the two earlier stages, likely due to increased activity by the adult birds (feeding of the nestlings and defecating) and less time by the adult birds for self-preening and nest sanitation. No positive relationship was found between bacterial counts and either egg mortality, nestling mortality or brood size; however, a negative relationship between egg mortality and total bacterial count was identified. Although somewhat unexpected, this negative relationship may indicate the presence of a greater number of symbiotic bacteria, which could offer a greater level of protection.

The Wryneck Jynx torquilla has undergone one of the largest bird species’ declines in Europe as a consequence of agricultural intensification; however, in some regions it still occurs in intensively managed permanent crops (e.g. vineyards). Considering the conservation status of the Wryneck and the increasing extent and intensification of permanent crops over Europe, investigating the habitat selection and use of nesting sites of this species in these ecosystems is urgently required. With this aim, we studied territory-scale habitat selection in a Wryneck population inhabiting a vineyard-dominated landscape without conservation measures for this species (e.g. nest box supplementation) in northeast Italy, and provide a preliminary assessment of its breeding biology. We evaluated the effect of land cover, management, and nest site availability on Wryneck occurrence in 44 territories and an equal number of control plots. In the year following this evaluation, Wryneck nests were surveyed in a subset of simple landscapes (

Nest abandonment prior to laying is poorly understood and rarely studied. One possible explanation is that it is a behavior which may have evolved in response to high predation risk in nesting birds as a strategy to avoid the even greater costs of losing eggs or chicks. We tested this hypothesis in the Grey Fantail (Rhipidura albiscapa), a species that builds and abandons multiple nests throughout its breeding season without laying eggs. We placed artificial nests (that contained natural and plasticine eggs) in the exact locations of natural nests from the previous breeding season (spanning a large elevational gradient) for which the fate was known (abandoned, predated, or fledged). Trials were conducted early and late in the breeding season to test for temporal patterns. We postulated that should nest abandonment indeed reduce predation risk, then artificial nests placed at previously abandoned nest sites should have a greater risk of predation than nests placed at predated or fledged nest sites. Overall, we found that 74% of artificial nests were predated, with predation attributed to birds (66%), small mammals (7%), ants (8%), and unknown predators (19%). Artificial nest predation varied according to previous nest fate, whereby predation rates were lowest for predated sites, slightly higher for fledged, and highest at previously abandoned nest sites. In addition, cover increased survival rates for all nest site types. However, we observed a shift in the proportion of nests predated by birds versus other predator taxa, whereby nest predation by birds was highest late in the season at high elevation; this increase may have been due to extreme high temperatures at low elevation resulting in bird predators moving to refuges at higher elevation.

Predation is a significant cause of nest failure in passerine birds, and, thus, natural selection is expected to favor behavioral plasticity to allow birds to respond to perceived changes in predation risk. However, behavioral plasticity in response to perceived predation risk, and its potential fitness-related costs, are understudied. In a wild population of breeding house wrens (Troglodytes aedon), we tested the hypotheses that (1) birds show behavioral plasticity in response to perceived nest-predation risk to reduce self-risk or risk to offspring, but (2) this plasticity incurs fitness-related costs. We experimentally increased the perceived risk of nest predation by enlarging the diameter of the nestbox entrance from the standard 3.2 cm to 5.0 cm once incubation began. Unexpectedly, large-hole females spent significantly less time being vigilant than small-hole (control) females during late incubation. Both males and females also exhibited plasticity in their provisioning behavior. Large-hole males increased and large-hole females decreased provisioning visits with increasing brood size, whereas small-hole males and females behaved similarly and were unaffected by brood size. Females did not show plasticity in their incubation or brooding behavior. Notwithstanding this behavioral plasticity in response to increased perceived predation risk, treatment had no effect on hatching success or early hatchling survival, nor did it affect nestling body condition or fledging success. We conclude, therefore, that house wrens show behavioral plasticity in response to perceived nest-predation risk, but that any short-term fitness-related costs associated with this flexibility appear negligible.

A nest of Phylloscartes oustaleti (Sclater, 1887), collected in the state of Santa Catarina, southern Brazil, is described as an ovoid structure with a dome-shaped lateral entrance supported laterally by thin twigs of a shrub. Building material was slender plant fiber interwoven with strands of live moss, which was growing also on twigs around the nest, thus serving to camouflage it. Egg cup was lined by silky material, probably seed down. This nest was found on 13 December 2007 when an adult was spotted carrying food to the nest, located 2.3 m above ground on the edge of secondary forest. Only arthropods were identified in the provisioned food, including mainly insects, but also spiders. General features of this nest conform to those of the few other species of the genus whose nests are known. Available records of Oustalet's Tyrannulet nests are consistent with the previously postulated September to December breeding season for the species, although one record of a bird carrying nest material in early August suggests the breeding season may extend earlier. Detailed nest descriptions are needed from a larger number of species before intra- and interspecific variation in nesting can be adequately appreciated in evolutionary or purely taxonomic contexts in this genus.

Documenting the adaptations of birds to live in urban areas is important in a context of an anthropogenically altered world where such areas may represent novel ecological opportunities for birds. Here I report on a nest of the Narrow-billed Woodcreeper Lepidocolaptes angustirostris in a wooden mailbox in a suburban area. The nest was found in the first week of November 2016 with three eggs, and later two nestlings that died within approximately one week likely due to water leaking into the box. The ability of L. angustirostris to use man-made structures for foraging and nesting, and its typical occurrence in open areas (thus differing from the family pattern of predominantly forest species) are factors permitting the occupation of urban habitats.

Flushing distance (FD, the horizontal distance between a parent bird when it leaves its nest and an approaching predator) is one measure of nest defense and of risk-taking; parents that stay too long risk being killed, whereas those that flush too early risk at the very least impairing development of their young, and at the very worst leaving them unprotected against predators. Thus, FD should be under strong natural selection. A general prediction is that incubating birds will remain on a nest being approached by a predator until risks of staying reach a threshold that outweighs costs of fleeing. This threshold is predicted to vary depending on a brood’s value, parental characteristics, environmental conditions, and learning that repeated visits pose a limited or no threat. We evaluated FD in a nest box population of tree swallows (Tachycineta bicolor) relative to each of these. We obtained 246 FDs from 66 different nests over 2 years. We found some evidence that FD increased with clutch size (tendency), female age, and air temperature, and decreased with greater overhead vegetation density; six additional associations were not significant. Given the lackluster support for the predictions we tested, we did a review of the literature and similarly found limited support for most of the associations we tested despite the entrenched view that these relationships are commonplace. We submit that further insights are needed into understanding predictors of FD in incubating birds. Parent birds sitting on eggs are proverbial sitting ducks, although they do have the option of fleeing predators. However, parents may be willing to sacrifice themselves to protect their eggs if the latter become sufficiently valuable. One assumption is that eggs increase in value closer to hatch, and one prediction is that parents will be more reluctant to fly from their nests later in incubation. We tested this and other predictions in a population of nest-box-using tree swallows in eastern North America. The relatively weak support we obtained for our predictions suggests that we need to reevaluate our assumptions in this area of research.

International audience; AbstractA variety of solitary bee species that naturally nest in wood and plant stems aboveground also readily accept nest boxes, which are human-made devices that aggregate these nesting conditions. Nest boxes are sheltered bundles of hollow plant stems, bamboo or reeds, and holes drilled into wood or cavities made of other materials such as glass or polystyrene. In this paper, I examine the best practises in nest box material selection and construction, and the use of nest boxes to address four basic objectives related to our understanding of bee biology and enhancement of pollination services. A variety of materials and cavity dimensions are included in nest boxes that are used to monitor local bee diversity or to address fundamental questions in community ecology and environmental change. Others examine bee biology, physiology and behaviour that use nest boxes to obtain bees for further experimentation. The majority of studies use nest boxes in agricultural landscapes and in alternative pollinator management; these studies improve nest box design for target bee species to augment their numbers. Continued design and data sharing, as well as the refinement of nest box construction and deployment for specific objectives, will ensure they remain useful tools for bee science, conservation and alternative pollinator management.

Urbanization brings dramatic and sudden changes to ecological conditions affecting natural communities. Cavity-nesting birds, both primary and secondary (hereafter PCN and SCN, respectively), may be limited in this novel environment because of reduced abundance of nesting sites (e.g. snags and cavities) and competition for cavities with non-native species. But humans can also directly and indirectly provide nest sites (e.g., nest boxes, crevices on houses), especially for SCN species, potentially partially compensating for negative effects. We investigated whether and how PCNs and humans facilitated the cavity-nesting bird community along a gradient of urbanization. To do so, we estimated the abundance of cavity-nesting species between 1998 and 2010 at 135, 1-km2 sites that differed in the degree of urbanization (0–100 % forest cover). Also, we found 367 nests on a subset of 31 sites. PCNs (n = 67 nests) nested mostly on snags (98.5 %), while native SCNs (n = 141) used both natural (71.63 %) and anthropogenic (28.37 %) cavities. Non-native SCNs (n = 159 nests) used mostly anthropogenic cavities (98.11 %). PCN abundance facilitated native SCN abundance on sites with more than 12 % forest cover at 1-km2 scale, but not at less forested sites. There, native SCNs nested primarily (59 %) in anthropogenic cavities. Human facilitation allowed native SCNs to successfully use and reproduce where snags were scarce, changing the composition and structure of the cavity-nesting bird community within the most urbanized sites. Flexible nest site selection and human facilitation provide new opportunities for native cavity-nesting birds in a rapidly changing world.

Avian nests function to provide a safe environment for parents, eggs and nestlings. Positive associations between nest size and other components of breeding performance are expected in two conditions. First, larger nests protect nest occupants better against environmental fluctuations (e.g., weather) than smaller nests. This implies that nest size is a determinant of survival in nest occupants. Second, if reproduction is physically costly, “stronger” parents are expected to be able to build both larger nests and rear more offspring. Here we present the findings of a 17-year correlative nest box study in Corsican Blue Tits (Cyanistes caeruleus ogliastrae) that examined the associations between nest size and different aspects of breeding success. We found that females with larger nests produced more fledglings, but did not produce more hatchlings or heavier nestlings than females with smaller nests. The analyses involving nest size controlled for other female characteristics (first-egg date, clutch size, female age) and environmental factors (oak habitat type, weather during the nestling stage) which we assumed could influence aspects of breeding success. Our findings concerning associations between the size of the nest and breeding success differ from those reported in previous studies in other geographic regions, perhaps because the costs that are associated with reproduction or the local environmental conditions that influence breeding performance are population specific. Our correlative study illustrates that avian studies of niche construction may benefit from long-term multi-factor investigations.

Few cases of adoption have been reported in solitary breeding raptors, and in owls adoption has only been reported in two species. Here we report four cases of brood-switching of juvenile Tengmalm’s Owls (Aegolius funereus), recorded during and after the post-fledging dependence period using radio-telemetry, and a case of three orphaned siblings (one nestling and two fledglings) originally from one nestbox successfully fostered to another one. A possible evolutionary context of the brood-switching is discussed.

We studied nestling food of three species breeding in Mediterranean oak woodlands that collect food in different niches of trees: blue tit (Cyanistes caeruleus; foliage-gleaner), great tit (Parus major; bark–foliage-gleaner) and nuthatch (Sitta europaea; bark-gleaner) in 2013–2014. Species-specific functions were compared using size and composition of preyed caterpillars, and nest-boxes were used in a before-after control-impact (BACI) design to test increase in breeding densities by providing nest-boxes. Our results demonstrate a high importance of caterpillars in the nestling diet of the three passerine species and suggest their complementary predation on early and late instars of the same Lepidoptera species. According to results of our BACI experiment, species’ breeding density increased by providing nest-boxes, with blue tit showing the highest difference in percentage change between manipulated and control plots (38.2, 26.8 and 14.3 % for blue tit, great tit and nuthatch, respectively). Overall, we highlight the combined functions of different tree-foraging guilds in caterpillar predation and propose nest-box provision as a management method to prevent defoliator outbreaks in Mediterranean oak woodlands.

It has been suggested that predators may protect human health through reducing disease-host densities or selectively preying on infected individuals from the population. However, this has not been tested empirically. We hypothesized that Tengmalm's owl (Aegolius funereus) selectively preys on hantavirus-infected individuals of its staple prey, the bank vole (Myodes glareolus). Bank voles are hosts of Puumala hantavirus, which causes a form of hemorrhagic fever in humans. Selective predation by owls on infected voles may reduce human disease risk. We compared the prevalence of anti-Puumala hantavirus antibodies (seroprevalence), in bank voles cached by owls in nest boxes to seroprevalence in voles trapped in closed-canopy forest around each nest box. We found no general difference in seroprevalence. Forest landscape structure could partly account for the observed patterns in seroprevalence. Only in more connected forest patches was seroprevalence in bank voles cached in nest boxes higher than seroprevalence in trapped voles. This effect disappeared with increasing forest patch isolation, as seroprevalence in trapped voles increased with forest patch isolation, but did not in cached voles. Our results suggest a complex relationship between zoonotic disease prevalence in hosts, their predators, and landscape structure. Some mechanisms that may have caused the seroprevalence patterns in our results include higher bank vole density in isolated forest patches. This study offers future research potential to shed further light on the contribution of predators and landscape properties to human health.

Observations and video documentation of interactions between animals living in dens, cavities, and other enclosed spaces are difficult, but they play an important role in field biology, ecology, and conservation. For example, bird parents visiting nests and feeding their nestlings may provide crucial information for testing of ecological hypotheses and may easily attract attention of participants of citizen-science ecological and conservation projects. Because of the nest concealment of cavity-nesting birds, their behaviors in the nest can only be studied by using video surveillance. Professional wildlife surveillance systems are extremely expensive. Here, we describe an inexpensive video setup that can be constructed with relatively little effort and is more affordable than any previously described system. We anticipate that the relatively low cost of about 250 USD for a battery-operated system is an important feature for citizen-science type of projects and for applications in heavily populated areas where the potential for theft and vandalism may be high. Based on our experiences, we provide methodological advice on practical aspects of using this system in the field for ecological research on birds. We highlight the low cost, easiness of construction, and potential availability to a large number of observers taking part in wildlife monitoring projects, and we offer technical help to participants of such research projects.

An overlap in attributes of nest cavities used by Great Tit Parus major across Eurasia suggests similar nest site preferences within the geographical range, although the drivers of these preferences are unclear. To determine whether preferred cavities provide conditions enhancing successful reproduction, we investigated the breeding performance of Great Tits in relation to tree cavity characteristics using data collected during 2008–2011 in primeval conditions (Białowieża National Park, Poland). Here, tree cavities are diverse and superabundant but nesting birds are at risk from a variety of predators. According to expectations, nest losses were high (60 % of Great Tit nests failed), mostly due to predation (69 % of nest failures). The risk of nest failure varied with nest cavity attributes. Compared to successful nests, failures were situated higher above the ground and placed closer to the cavity entrance. Very deep cavities with narrow entrances and strong livings walls provided effective protection against larger predators (e.g., martens, woodpeckers), unable to enter the cavity or pull out the contents. Yet, such holes were no barrier for the smallest predators (e.g., Forest Dormouse Dryomys nitedula), which were able to enter any Great Tit nest cavity and destroyed most of the nests. Avoiding small predators would give a selective advantage to the birds, but this seems hardly possible to achieve. We conclude that tree cavities preferred by the tits show a combination of properties which are a compromise for avoiding predation (the strongest selective pressure) and providing the minimum requirements (sufficient nest illumination, microclimate, protection against nest soaking) for development and growth of young.

Social selection is expected to favour the evolution of female aggressive defence of nesting resources in cavity-nesting birds, which may be also mediated by testosterone (T) levels. Male T levels could express male dominance and thereby territorial safety for female partners and thereby reduce their need for aggressive defence. Here, we explored the role of T levels in female-female competition in a songbird, the pied flycatcher Ficedula hypoleuca. In an experiment with female decoys placed close to the nestbox at the end of laying, we explored if female aggressiveness is related to their own T level or to mate T level. T levels of males and females were measured in the middle of the nestling period. Mean female aggressiveness towards decoys in three presentations was estimated through proximity to the decoy and number of attacks by females, two variables which were positively associated. Aggressiveness by female nest owners to female decoys was negatively related to male T level but unrelated to own T level. There was no assortative mating with respect to T level. Female aggressiveness is more strongly related to the hormonal status of mates than to their own., The study has received financial support from project CGL2013-48193-C3-3-P to JM (DGI-Ministerio de Ciencia e Innovación).

Nest prospecting, that is, visiting potential future nest sites, may be a widespread bird behavior. Here we describe apparent prospecting while nesting by white-rumped swallows (Hirundinidae, Aves). In southern Brazil, birds tagged with passive-integrated transponders (PIT-tags) and breeding in nest boxes with PIT-tag readers: (1) often visited nest boxes that were in use by apparently unrelated birds (54 % of nests were visited at least once), (2) visited other boxes while caring for their own nestlings, (3) tended to have smaller broods than birds that were not recorded visiting, and (4) did not have a preference for any particular box. These patterns do not indicate any clear explanation for nest visiting, but they do show that prospecting is done by floaters (non-breeders) as well as actively breeding individuals. We suggest that these visits occur when time is available and that visitors may be assessing the availability of future nest sites.

Itishypothesizedthatvariation inimmunefunction between individuals is due to costs incurred to sustain it. Sup- port for this hypothesis mostly comes from short-term studies on the either costs of innate responses or a combination of innate and antibody responses. Key studies on the fitness and physiological costs of acquired immunity, in which the antibody response is specifically stimulated over a long peri- od, are lacking. We specifically stimulated the antibody re- sponse against a virus (Newcastle virus) in male European starlings (Sturnus vulgaris) for 2 months to test whether im- munization reduces a fitness-related trait (song rate) and in- creases oxidative stress. Immunization did not affect the total song rate, but it caused a reduction of the undirected song rate (produced away from the nest box and mostly used for estab- lishing dominance hierarchy). We also found that immunized birds had a lower nest-box-oriented song rate (mostly used to attract females) than control birds although the interaction between treatment and sampling period was not significant. Immunization did not cause any changes in the blood oxida- tive status. Starlings with a higher nest-box-oriented song rate had significantly lower levels of oxidative protein damage. Finally, starlings that skipped the antibody response had an oxidative status similar to that of starlings that produced anti- bodies, but they had overall a lower rate of undirected song. Our results suggest that (i) immunized starlings preserved the song used to attract mates but not that used in social interac- tions and (ii) the antibody response incurs costs that are reflected in the expression of song, but also that these costs are unlikely to be determined by oxidative stress. Our results also suggest that bird song might convey information about a male's oxidative status.

Recent studies indicate that polymorphisms of the DRD4 gene may be related to behavioural variation in mammals and birds. The purpose of this study was to ascertain a connection between DRD4 genotypes and behavioural patterns in a wild passerine bird during breeding time. We evaluated changes in birds’ parental provisioning behaviour in the presence of a novel object. As a behavioural trait, we measured the duration of feeding interruption from the first time that each bird noticed the novel object until they entered the nest box. We found a gender-specific association between DRD4 gene polymorphism and parental behaviour. Males with a CC genotype delayed feeding for a longer period than those with CT and TT genotypes. No significant effect of genotype on provisioning behaviour was observed among females. We conclude that (i) DRD4 gene polymorphism in wild birds can be associated with behaviour related to fearfulness, and (ii) this effect is supposedly gender-specific during the breeding time, potentially explained by sex differences in parental care or hormonal levels.

While rural House Sparrows (Passer domesticus) have declined in Sweden, the population of the related Tree Sparrow (P. montanus) has remained stable, suggesting that they are affected by different population regulating mechanisms. Here we investigated if the two species differ in degree of nest-site limitation. After conducting an initial survey of both species on farmsteads in southern Sweden, we supplemented a subset of farms with additional nest-boxes. The farmsteads were resurveyed 3–4 years later to compare any change in population sizes for the two species between farms with and without added nest-sites. We also considered the availability of other nest-sites by counting the number of tile-clad buildings on the farmsteads. We did not find any effect of adding nest-boxes on House Sparrow population sizes, but a significant increase in the population estimate of Tree Sparrows. The number of Tree Sparrows was related to the availability of tile-clad buildings, whereas no such relationship was found for House Sparrows. At low and intermediate population sizes, House Sparrow nest-box utilization declined with the number of tile-clad buildings, suggesting preference for nest-sites under tiles when available. Our results suggest that while Tree Sparrow populations in the southern Swedish farmland are nest-site limited, House Sparrow populations are mainly limited by other mechanisms. Our results suggest that nest-site limitation is unlikely to explain the stronger population decline in rural House Sparrows compared to Tree Sparrows and that nest-site addition is unlikely to be an efficient remedy for the rural House Sparrow decline.

The American Kestrel (Falco sparverius) is one of North America’s most common raptors. However, recent data reveals a decrease in the number of individuals at both migration and nesting sites, sparking concern that the North American subspecies (F. s. sparverius) may be in decline. In this study we used long-term monitoring data to examine whether a decrease observed in a study population of breeding F. s. sparverius in the boreal forests of Saskatchewan over the past two decades coincided with a loss in genetic diversity. While count data collected showed a significant decline in occupancy of nest boxes, genetic summary statistics and Bayesian modeling methods revealed evidence for a population expansion occurring in the decades directly before the start of the nest box program. The initial contradictory nature of the count and genetic data was resolved when the results examined together revealed that the detected changes in population size coincided with changes in land-use around the study site, suggesting that the shifts in numbers of F. s. sparverius may represent the subspecies’ ability to respond rapidly to changes in suitable habitat. This study highlights the importance of integrating both genetic and population data into studies that examine changes in population size, especially for a migratory species where the connections between breeding sites and landscape changes may be fluid and rapid.

Parents may feed nestlings based on positional cues resulting from sibling competition for favored positions at the front of a nest cavity, or they may assess begging intensity regardless of location within the nest. We independently manipulated proximity to the nest entrance and hunger level to determine whether western bluebird (Sialia mexicana) parents favor hungrier nestlings or instead feed nestlings closest to the nest entrance. We used a balanced design to vary hungry and fed nestlings between the back and front of the nest box. We deprived half of the nestlings in each brood of food for an hour, and then, each nestling was constrained using Plexiglas dividers to a quadrant in the nest box. We videotaped inside the box to assess begging intensity and food delivery to individual nestlings. Hungry nestlings begged more intensely and received more food than fed nestlings, regardless of their proximity to the nest entrance. However, when delivering the first feed to nestlings, parents favored front nestlings over hungry nestlings, possibly due to a bias resulting from the manipulation, which involved replacing and rearranging nestlings after a 1-h period. Overall, parents did not favor nestlings in the front of the nest over those in the back. Parents therefore are able to distinguish hungrier nestlings and preferentially feed them under favorable environmental conditions, when brood reduction is uncommon. When parents choose which offspring to feed, they may assess begging signals, which can include movements and vocalizations that vary in intensity. Alternatively, cavity-nesting species may use simple rules such as favoring offspring that have pushed to the front of the nest. We conducted an experiment to determine whether western bluebird (Sialia mexicana) parents would preferentially feed hungry nestlings over fed nestlings when Plexiglas dividers prevented competition and equalized the frequency with which hungry and fed nestlings were in the front versus back of the nest. After depriving half of each brood of food for an hour, we measured begging intensity and food delivery. Parents preferentially fed hungrier nestlings, which begged more intensely, regardless of their position in the nest, indicating that parents are able to distinguish between hungry and fed nestlings.

Animals constantly need to acquire information about the environment for settlement decisions, either by using a trial-and-error strategy or by using public information by monitoring conspecifics. We studied a nest box population of Eurasian kestrels Falco tinnunculus in western Finland to test if pellets and other prey remains accumulated on the bottom of nest boxes are used as public information during settlement. During 2002–2013, nest boxes were randomly cleaned (treatment) or left un-cleaned (control) in each season. It is possible that kestrels reuse nest boxes which include information of successful nesting (i.e. have not been cleaned) because they indicate previous breeding attempt at the site. At the same time, this decision may entail costs because of blood-sucking ecto-parasites like Carnus hemapterus overwintering in the layer of pellets. First, we found that egg-laying date was significantly earlier in un-cleaned control boxes than in cleaned treatment boxes, indicating the use of public information revealed by pellets in the settlement decision. Second, the ecto-parasite burden of young nestlings (age 6–15 days) was significantly higher in un-cleaned control nest boxes. We found higher ecto-parasite infestation in early and lower infestation in late nests, a seasonal trend that is in disagreement with the ecto-parasite avoidance hypothesis. Contrary, in overall lower-infected cleaned boxes, ecto-parasite prevalence remained equal throughout the season. However, the ecto-parasite burden had no obvious effect on breeding success. We conclude that the use of pellets revealing successful breeding attempt of the previous year as public information appeared to be important in the settlement decision of kestrels.

The Neotropical woodpecker Melanerpes candidus is one of the few bird species known to attack wasp or bee colonies to feed on the brood and honey of these colonial stinging insects. I describe herein a foraging tactic that lessen the risk posed by the nest-defending Paulistinha wasps (Polybia paulista) and allows this woodpecker to feed on the brood with no or little disturbance by the wasps. The bird taps repeatedly on the branch that supports the paper wasp nest, about 2-3 m below the nest. During this process, the nest-defending wasps attack the woodpecker. When the attack is intense, the bird retreats from the nest vicinity only to return instants later. After a while, the woodpecker climbs slowly but steadily towards the nest while tapping continuously, the wasps retreating to the nest top and fleeing away. With the nest largely wasp-free, the bird perches on the nest and preys on the brood. This subtle foraging tactic of M. candidus and its driving the wasps away from their nest contrasts with the sudden, rash, and nest- damaging attacks described for other bird species that prey on wasp and bee broods, such the Neotropical falcon Ibycter americanus and the Old World buzzards of the genus Pernis.

There is growing evidence that birds are able to discriminate different types of nest intruders and adjust their nest defence behaviour according to intruder dangerousness and distance from the nest (the dynamic risk assessment hypothesis). Here, we tested whether birds’ decisions about nest defence may additionally be affected by an increasing familiarity with a particular nest predator. We tested nest defence responses of great reed warblers Acrocephalus arundinaceus to a nest predator, the little bittern Ixobrychus minutus. Great reed warbler nests located close (≤7 m) to synchronously breeding little bitterns were “neighbour”, other nests were “solitary”. Great reed warbler specific aggression towards a little bittern dummy was much lower (~5-times) at neighbour than solitary nests. In contrast, generalised responses to a control innocuous intruder (the turtle dove, Streptopelia turtur) were statistically identical at neighbour and solitary nests. These patterns are in line with dynamic risk assessment hypothesis. We hypothesise that decreased great reed warbler aggression at neighbour nests also represents a specific behavioural adaptation to nesting in association with the little bittern. Little bitterns breeding closer to great reed warblers showed decreased risks of failure due to predation. However, further research is needed to experimentally test the causal links behind these patterns.

The abiotic conditions of the immediate environment of organisms are key factors for a better understanding of ecological and evolutionary processes. Yet, information in this regard is biased towards some habitat types, landscapes, and organisms. Here, we present a 2-year comparative study of the microclimatic properties (temperature, relative humidity, and their fluctuation) of three cavity types (nest boxes, cavities in bridges, and burrows in sandy cliffs) in an arid environment. We found marked and consistent months-long differences in microclimate among the three cavity types. Nest boxes were colder than the other cavity types, with temperature oscillations being an order of magnitude higher than in other cavity types. In contrast, microclimate was very stable in burrows and cavities in bridges, the former being generally warmer and drier than the latter. We also discuss the biological implications of microclimatic conditions and its variation in different cavity types by presenting two case studies, namely the temperature-humidity index and water vapor pressure during the hatching period of an endotherm and the chilling period during the diapause of an ectotherm ectoparasite. We stress the need for comparative studies of the same organisms subjected to different microclimates given the important ecological, evolutionary, and conservation implications.

Communal nursing, the provision of milk to non-offspring, has been argued to be a non-adaptive by-product of group living. We used 2 years of field data from a wild house mouse population to investigate this question. Communal nursing never occurred among females that previously lacked overlap in nest box use. Females nursed communally in only 33 % of cases in which there was a communal nursing partner available from the same social group. Solitarily nursing females were not socially isolated in their group; nevertheless, high spatial associations prior to reproduction predict which potential female partner was chosen for communal nursing. An increase in partner availability increased the probability of communal nursing, but population density itself had a negative effect, which may reflect increased female reproductive competition during summer. These results argue that females are selective in their choice of nursing partners and provide further support that communal nursing with the right partner is adaptive. Electronic supplementary material The online version of this article (doi:10.1007/s00114-013-1130-6) contains supplementary material, which is available to authorized users.

The stochasticity in food quality and availability, and physical trail characteristics experienced by leaf-cutter ants, may favour individual flexibility in load-mass selection so as to forage effectively. The present study aimed to confirm previous evidence, from Atta cephaoltes foragers, of variable load-mass selection in response to steep inclines and declines in the leaf-cutter ant Acromyrmex octospinosus. The foraging trail gradient of a captive colony of Ac. octospinosus was manipulated by altering the position of a foraging platform relative to the nest box. The results indicate an effect of steep gradients on walking speed and variation in load mass in relation to gradient as a result of individual plasticity, not recruitment of different-sized individuals. Ants selected heavier loads when returning to the nest vertically downwards than when returning horizontally or vertically upwards. These results are discussed with reference to foraging performance. Walking speed was considerably reduced on upward returns to the nest, but was also slower when travelling vertically downwards compared with horizontal trails, suggesting vertical trails per se impact on the time costs of foraging. Differences in load-mass selection were evident from the onset of foraging and did not change significantly over the course of 24 h, suggesting this behaviour was based on individual experience, rather than colony-level information feedback. The present study has demonstrated that Ac. octospinosus foragers are capable of individual flexibility in load-mass selection in response to a physical trail characteristic that is pertinent to their natural habitat and is a factor seldom considered in theoretical foraging models.

Although animal population dynamics have often been correlated with fluctuations in precipitation, causal relationships have rarely been demonstrated in wild birds. We combined nest observations with a field experiment to investigate the direct effect of rainfall on survival of peregrine falcon (Falco peregrinus) nestlings in the Canadian Arctic. We then used historical data to evaluate if recent changes in the precipitation regime could explain the long-term decline of falcon annual productivity. Rainfall directly caused more than one-third of the recorded nestling mortalities. Juveniles were especially affected by heavy rainstorms (≥8 mm/day). Nestlings sheltered from rainfall by a nest box had significantly higher survival rates. We found that the increase in the frequency of heavy rain over the last three decades is likely an important factor explaining the recent decline in falcon nestling survival rates, and hence the decrease in annual breeding productivity of the population. Our study is among the first experimental demonstrations of the direct link between rainfall and survival in wild birds, and clearly indicates that top arctic predators can be significantly impacted by changes in precipitation regime.

Animals can estimate breeding habitat quality by monitoring social information provided by the behaviours of others. While it is accepted that the value of public information erodes with distance from the source of information, the spatial and temporal ecology of public information acquisition and use is not well understood. Published accounts of the acquisition of public information for breeding habitat selection show a study bias towards the period corresponding to the breeding season. Here, we explored the idea that post-breeding courtship is a reliable source of performance social information about breeding habitat quality that can be used by nest-site prospectors. We revealed that post-breeding courtship can be used as performance social information for breeding habitat selection in a sedentary, cavity-nesting bird species, the Eurasian Tree Sparrow Passer montanus. First, the occurrence of the autumn nest at a nest box was positively associated with the nest box’s breeding performance in both the preceding and subsequent breeding seasons. Second, nest boxes with owners that showed higher post-breeding courtship activities attracted more prospectors. Namely, more prospectors visited nest boxes momentarily occupied by both owners and containing complete autumn nests at the end of autumn compared to nest boxes momentarily occupied by single owners and containing incomplete autumn nests. We suggest that post-breeding courtship represents performance social information about breeding habitat quality that is accessible to more potential observers than performance social information available during the breeding period is. Also, post-breeding courtship can be even more reliable performance social information than that available during the breeding period because it integrates information provided by informed individuals on the nest site’s breeding performance and post-breeding attractiveness (i.e. use).

Our understanding of the annual life-cycle movements of small migratory birds has advanced rapidly with the advent of light-weight geographical positioning devices (i.e., geolocators), yet the effects of geolocators on reproduction and survival have not been adequately quantified. We tested for impacts of attaching a 1-g geolocator (using a harness around the legs and back, anterior to the tail) to adult Tree Swallows (Tachycineta bicolor) on parental feeding behavior, nestling growth and size, fledging success, and return rates between 2011 and 2012. At one breeding site, we compared feeding visits, nestling growth, and nestling size between paired nest boxes where one parent was marked at the 'geolocator' box with a 'control' nest box where neither parent was marked. We detected no differences between geolocator and control nests in either the frequency of feeding visits to nestlings or the amount of time spent at nests. Birds marked with geolocators fed nestlings as frequently as their unmarked mates. Likewise, nestlings raised at geolocator nests grew at similar rates to those at control nests, and had similar structural size and body mass at fledging. At three widely-separated sites across the Tree Swallow breeding range in Canada, we also found that fledging success was similar for geolocator and control nests. Although we found no evidence for short-term negative impacts of geolocators, the return rates of geolocator-marked Tree Swallows tended to be significantly lower than those of unmarked control birds. Thus, we found little evidence for short-term impacts of geolocators on reproduction but our study does suggest that long-term impacts of geolocators could be manifested in terms of lower survival, higher emigration rates, or lower breeding propensity. © 2013 Dt. Ornithologen-Gesellschaft e.V.

Introduced species pose a major threat to biodiversity across the globe. Understanding the impact of introduced species is critical for effective management. Many species around the world are reliant on tree cavities, and competition for these resources can be intense: threatening the survival of native species. Through the establishment of 225 nest boxes, we examined the relationship between tree density and the abundance and nesting success of three bird species in Canberra, Australia. The common myna (Acridotheres tristis) is an introduced species in Australia, and the crimson rosella (Platycercus elegans) and eastern rosella (Platycercus eximius) are native species. We then investigated the impact of common myna nest box occupation on crimson rosella and eastern rosella abundance. Tree density significantly influenced the abundance and cavity-nesting of all three species. Common myna abundance (birds per square kilometer) was greatest at low tree density sites (101.9 ± 22.4) and declined at medium (45.4 ± 10.1) and high (9.7 ± 3.6) tree density sites. The opposite pattern was observed for the crimson rosella, with greater abundance (birds per square kilometer) at high tree density sites (83.9 ± 9.3), declining over medium (61.6 ± 6.4) and low (31.4 ± 3.9) tree density sites. The eastern rosella was more abundant at medium tree density sites (48.6 ± 8.0 birds per square kilometer). Despite the strong influence of tree density, we found a significant negative relationship between common myna nest box occupancy and the abundance of the crimson rosella (F 1,13 = 7.548, P = 0.017) and eastern rosella (F 1,13 = 9.672, P

Since dormice usually use natural tree hollows or artificial nest boxes as nest sites and these nests are reused from 1 year to another, the present study investigated how the parasite loads from old nests affected the behaviour of the forest dormouse Dryomys nitedula Pallas, 1778. Dormice were subjected to three different experiments: 1. They were given the choice of a nest box infected with ectoparasites and a new unused nest box; 2. Dormice were given the choice of a treated (uninfected) previously used nest boxes and previously used nest box that was infected; and 3. Using infrared motion sensor cameras, we tested weather they preferred to avoid nest boxes when only infected nests were available. The results revealed that the females with pups are pickier when choosing the nursery site. These preferred empty nest boxes or nest boxes with treated nests instead of the infested ones. However, non-breeding adults and sub-adults showed indifference to the flea infestation of the nest.

The microclimate of potential roost-sites is likely to be a crucial determinant in the optimal roost-site selection of endotherms, in particular during the winter season of temperate zones. Available roost-sites for birds and mammals in European high trunk orchards are mainly tree cavities, wood stacks and artificial nest boxes. However, little is known about the microclimatic patterns inside cavities and thermal advantages of using these winter roost-sites. Here, we simultaneously investigate the thermal patterns of winter roost-sites in relation to winter ambient temperature and their insulation capacity. While tree cavities and wood stacks strongly buffered the daily cycle of temperature changes, nest boxes showed low buffering capacity. The buffering effect of tree cavities was stronger at extreme ambient temperatures compared to temperatures around zero. Heat sources inside roosts amplified Δ T (i.e., the difference between inside and outside temperatures), particularly in the closed roosts of nest boxes and tree cavities, and less in the open wood stacks with stronger circulation of air. Positive Δ T due to the installation of a heat source increased in cold ambient temperatures. These results suggest that orchard habitats in winter show a spatiotemporal mosaic of sites providing different thermal benefits varying over time and in relation to ambient temperatures. At cold temperatures tree cavities provide significantly higher thermal benefits than nest boxes or wood stacks. Thus, in winter ecology of hole-using endotherms, the availability of tree cavities may be an important characteristic of winter habitat quality.

The impact of nest-box characteristics (design, position, content) on decisions where to roost or nest have rarely been experimentally investigated. Older studies claimed that secondary cavity-exploiters, such as tits (Paridae), prefer smaller boxes for roosting and larger boxes for breeding. Surprisingly, these aspects of box preference have to our knowledge not been examined in choice experiments. We therefore allowed free-ranging birds to use, as roosting or nesting sites, three box designs attached together on the same support, covering the range of box sizes used to attract Great (Parus major) or Blue (Cyanistes caeruleus) Tits in long-term investigations. We observed that medium-sized and large boxes contained disproportionally more avian excrements before nesting than small boxes. The large boxes also contained disproportionally more body plumages prior to nesting and Great Tit nests. Nest-box size therefore influenced where the birds roosted and nested. Potential costs and benefits of exploitation of boxes differing in size are briefly discussed.

Journal of Comparative Physiology A, 199 (3), ISSN:0340-7594, ISSN:1432-1351

Nest boxes are commonly erected in managed landscapes such as backyards, golf courses and parks, attracting cavity-nesting birds to habitats they would not otherwise occupy. Although studies have shown that habitat around natural nests influences postfledging survival, this relationship has not been examined for artificial nest cavities, which humans may site at inappropriate locations. In Williamsburg, Virginia, we compared vegetation surrounding nest boxes which produced eastern bluebird fledglings that were predated by hawks within 10 days of leaving the nest to vegetation surrounding nest boxes producing surviving fledglings. We found a significant difference between PC scores for forest denseness around nest boxes that produced surviving versus predated fledglings; fledglings that survived tended to come from nest boxes with high forest and canopy cover, close trees and little grass.

Using nest boxes with different sized entrances, we experimentally examined whether a large species of cavity breeder (House Sparrow, Passer domesticus) affects the nest box occupancy and breeding success of a smaller species (Great Tit, Parus major), and whether there are differences in the effects of competition during different parts of the breeding season. Great Tits occupied nest boxes regardless of the number of House Sparrows breeding in the vicinity. During the second part of the breeding season, the percentage of successful Great Tit pairs was negatively correlated with the occupation of nest boxes by the House Sparrows, in both the large- and small-entrance nest boxes. More Great Tit pairs bred and more young were fledged in the small- than large-entrance nest boxes. Great Tits occupied more large-entrance nest boxes during the first than the second part of the breeding season. This difference was probably due to House Sparrows occupying more large-entrance nest boxes during the second than first part of the breeding season. 74 % of the large-entrance nest boxes in which Great Tits built nests in both the first and second parts of the season were later occupied by House Sparrows. Great Tits preferred large-entrance nest boxes in the fall, when House Sparrows use only a few boxes for roosting, but not for breeding. The findings indicate that Great Tits are subject to interspecific competition with House Sparrows for nesting cavities, the intensity of which varies during the breeding season and is higher during the second part when more House Sparrows breed.

Tree Swallows, Tachycineta bicolor, have been studied at nest box colonies at sites throughout North America. They can be easily aged, captured, repeatedly sampled, and their physiology and reproductive success measured across their lifetime. These traits have made Tree Swallows an important model species for many ecological and evolutionary studies. We have studied aging in free-living Tree Swallows colonies located in Iowa and New York, USA, for several years, and here we review what these studies are revealing about physiological attributes of senescence and their ecological and evolutionary consequences. Telomeres, the DNA “caps” on each chromosome, shorten with age, which may contribute to the senescing phenotype, and birds with longer telomeres at 1 year of age have a significantly longer predicted life span than birds with shorter telomeres. Tree Swallows display decreased cell-mediated immune function with age, but other components of the immune system do not decline with age. Older, nesting females who display immunosenescence also show exaggerated sickness behavior compared to younger birds in response to a simulated bacterial infection. Sickness behavior in old birds leads to loss of body condition and decreased parental behavior, suggesting that immunosenescence carries fitness costs in the wild. We are also carrying out an experimental test of the leading theory for aging–oxidative stress. Preliminary data from metabolically-handicapped Tree Swallows carrying an extra 5% of their body mass suggest birds may suffer increased oxidative damage and telomere shortening, reduced immune function, and lower reproductive success. Continued cross-sectional and longitudinal studying of Tree Swallows will enable us to distinguish between intrinsic change with age common to all birds and the results of selection on traits that affect survivorship and differ between individuals. Our results suggest continued work with Tree Swallows holds great promise to understand the evolutionary ecology of senescence in birds and other animals.

Predation has been suggested as an important factor affecting the success of breeding birds. Various studies have found that particular bird species either avoid or choose to breed in the proximity of predator nests. Here, we investigated whether the presence of a generalist predator, the Eurasian Kestrel, Falco tinnunculus, affects the breeding success of a passerine (House Sparrow, Passer domesticus), using an experimental design of nest box placement for the two species. No difference in breeding parameters was found with distance of House Sparrow nests from both active and inactive Kestrel nest boxes. However, whereas House Sparrows built nests and laid eggs in nest boxes both with and without active Kestrel nest boxes in the vicinity at a similar frequency, they laid more clutches, and the total number of eggs laid and young fledged during the breeding season was higher, in nest boxes located close to active Kestrel nest boxes than to inactive ones. Of the 367 House Sparrow nestlings banded, only 3 were found predated in Kestrel nests and no correlations were found between the percentage of birds in the Kestrels’ diet and breeding parameters of the House Sparrows. The proximity of breeding Kestrels may facilitate some protection to House Sparrows from other predators, such as corvids, which are chased away by Kestrels near the nest.

Relocation to novel nests (sometimes called drifting) in flying Hymenoptera is often interpreted as the result of navigation error and guard bees erroneously admitting foreign individuals into the nest. We studied nest fidelity and nest relocation of both females and males in a nesting aggregation of Xylocopa virginica in southern Ontario, Canada, where females can nest either solitarily or socially. Adult female and male bees were trapped at nest entrances, individually paint marked, and then released. Subsequent recapture patterns were used to assess nest fidelity: that is, how faithful individuals were to their home nest and how often they moved to another nest. Bees were considered to have relocated if they were recaptured in a nest different from the one in which they were initially trapped, indicating that they had spent at least one night in a new nest. Some females were only captured in one nest, some occasionally moved to new nests, temporarily or permanently, and a few were never caught in the same nest twice. In addition, females relocated to nests that were further away in 2007 when population density was low, suggesting that they seek out and claim nesting spaces when they are available. Males relocated more frequently than females, with most drifting from nest to nest in no obvious pattern. This indicates that males spend the night wherever space is available or in nests nearest to their territories. This study reveals that for both female and male X. virginica, nest membership is not as stable as once thought.

The effects of competition and risk of predation on secondary cavity breeders were examined between the 2008 and 2009 breeding seasons using an experimental design manipulating two nest entrance sizes (large entrances allowed Barn Owls (Tyto alba) to enter, while the small entrances excluded them). During the 2009 breeding season, the entrance sizes of nest boxes were exchanged, so that if during one year a nest box in a particular location had a small entrance, the second year it had a large entrance and vice versa. Barn Owls and Eurasian Kestrels (Falco tinnunculus) occupied 67.3 and 17.3%, respectively, of large entrance nest boxes. Significantly more Jackdaws (Corvus monedula), House Sparrows (Passer domesticus) and Scops Owls (Otus scops) bred in nest boxes with small than with large entrances. After nest box entrance sizes were exchanged, Barn Owls and smaller species did not breed in the same nest boxes with the new entrance size. Jackdaws probably did not breed in large entrance nest boxes due both to exploitation competition (Barn Owls and Eurasian Kestrels occupied the majority of large entrance nest boxes), and may also have avoided empty nest boxes because of the risk of interference competition; whereas smaller species may have also avoided large entrance nest boxes due to risk of predation.

The use of nest boxes by the woodland dormouse, Graphiurus murinus, was investigated over a 13-month period in a riverine forest of the Great Fish River Reserve, South Africa. We predicted that some characteristics of nest box placement would affect nest box use and that the seasonal pattern of nest box use would be linked to the species' life cycle and physiological and socioecological characteristics. Generalized linear models indicated that the time since nest box installation and nest box height above ground positively affected the frequency and intensity of nest box use. Male and female dormice, as well as adults and juveniles, did not differ in the number of nest boxes used and equally occupied individual nest boxes. The percentage of nest boxes used peaked during spring and summer (breeding period) and dropped during winter (hibernation). However, whereas significantly more males were caught during the mating season (spring), the number of females occupying nest boxes was constant during the year. As female dormice successfully bred in the nest boxes, the observed sexual patterns suggest that (artificial) nest sites represent an important resource for females, whereas females seem to constitute the main resource for males, as predicted by the socioecological model.