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Several hypotheses explain how sensory, anatomical and physiological constraints drive fruit preference in frugivores. Optimal diet theory (ODT) states that frugivores make decisions based on the energy contained in food. In contrast, geometry of nutrition (GN) states that animals balance their macronutrient intake instead, opting for rough energy. The defence trade-off hypothesis (DTH) assumes a negative relationship between secondary compounds and fruit preference. Finally, the size-matching hypothesis (SMH) states that frugivores are more attracted to fruits that are easier to handle and consume. We tested these four hypotheses by offering paired fruit species to three fruit-eating animal species in captivity that either chew fruit in the beak or mouth (‘masher’: 1 bird species, 1 bat species) or swallow whole fruits (‘gulper’: 1 bird species), from which we built a ranking of fruit preference. We then explored the importance of 13 fruit traits in explaining fruit preference. The masher bird was the only species whose fruit preference pattern corresponded with GN. Fruit preference of the masher and gulper bird species supported DTH and SMH, while fruit preference by the bat species was not related to any analysed trait. More than one single rule governs fruit preference in different frugivore species. Fruit preferences of functionally different frugivore species are affected by particular fruit traits, which they either select or avoid. The search for specific macronutrients, while avoiding toxicity in fruits matching the anatomical limitations of frugivores, could lead to complementary foraging choices. Variability between seed disperser species in their search for easily manageable fruits allows achieving a complementary fruit diet, with preferred and avoided traits. It can be an important driver of fruit trait diversity in fleshy-fruited plant assemblages.

The use of anvils for foraging allows access to food that cannot be exploited otherwise by most birds or other animals. This may be especially important in habitats where food resources are scarce or fluctuate seasonally and where animals exploit novel and highly nutritional food resources that require unconventional foraging techniques to acquire energy. In dry woodlands of northern Argentina, the White-fronted Woodpecker, Melanerpes cactorum, secures seeds from a shrub species, Sarcotoxicum salicifolium, by wedging the seeds into crevices, holes, or forks within plant structures, where they peck the hard cover of the seeds to extract the embryo. The aim of this study was to evaluate whether the anvil use by the White-fronted Woodpecker conforms to or differs from the anvil use by other woodpecker species. Specifically, we (1) described the behaviour of seed consumption mediated by using anvils in plant structures, and (2) analysed the use of anvils for seed consumption relative to seasonality and food availability in the dry Chaco of Argentina. The woodpecker matched the size of the seed to the anvil, and seeds were positioned mostly with a specific orientation pattern in structures of seven plant species, facilitating opening and extraction of the complete embryo. As in other anvil-using woodpecker species, this pattern of deliberate manipulation and orientation of seeds by the woodpeckers may imply spatial association of the seed and the site used as an anvil, a behaviour that could be cognitively more demanding than simply using an anvil. In contrast with other anvil-using woodpecker species, seed consumption mediated by anvil use was most important in summer (i.e. breeding season), when S. salicifolium seeds were more abundant but also when the availability of food resources was more diverse and abundant. The seed embryos are likely an important source of nutrients and more profitable than other less protected food resources for the White-fronted Woodpecker, particularly during the breeding season when energy demands increase.

The generalist diet of most frugivores opens a window of opportunity to the invasion of alien plants whit fleshy-fruits. The outcome of the new relationships between alien plants and native frugivores depends both on traits of the invaders and of the mutualist partners in the recipient community. Two contrasting hypotheses attempt to explain the integration of alien species in native communities. “Darwin’s naturalization hypothesis” proposes that alien species more different from native species are more likely to integrate in the community. The “similarity hypothesis” proposes the opposite, that alien species more similar to native species are more likely to integrate the native community. By comparing chemical and morphological traits of 12 alien and 48 native fleshy-fruited species, we tested both hypothesis as assembly rules of alien species in subtropical Andean forests. We did not find differences in most chemical or morphological traits between alien and native fruit species. The multidimensional variation of alien fruit traits was nested within that of native species. However, alien fruits tended to score high in the range of variation of native chemical traits. Accordingly, we propose the “fraction similarity hypothesis” as a main force that drive the assembly of alien species in mutualistic networks, i.e. alien species benefit from existing mutualistic interactions that involve fruit species with traits selected by the frugivores to invade native communities. The striking similarity in fruit traits between alien and native species highlights the potential role of seed dispersers as ecological filters to the invasion of alien plants. In turn, this similarity suggests that alien fruits can be functionally equivalent to native ones in terms of their interaction with fruit-eating birds.

Downsizing of animal communities due to defaunation is prevalent in many ecosystems. Yet, we know little about its consequences for ecosystem functions such as seed dispersal. Here, we use eight seed-dispersal networks sampled across the Andes and simulate how downsizing of avian frugivores impacts structural network robustness and seed dispersal. We use a trait-based modeling framework to quantify the consequences of downsizing—relative to random extinctions—for the number of interactions and secondary plant extinctions (as measures of structural robustness) and for long-distance seed dispersal (as a measure of ecosystem function). We find that downsizing leads to stronger functional than structural losses. For instance, 10% size-structured loss of bird species results in almost 40% decline of long-distance seed dispersal, but in less than 10% of structural loss. Our simulations reveal that measures of the structural robustness of ecological networks underestimate the consequences of animal extinction and downsizing for ecosystem functioning., Species loss from ecological networks can impair network stability and ecosystem function. Here the authors simulate animal extinctions in interaction networks between plants and avian frugivores, showing that frugivore extinctions have comparatively weak effects on network structure, but strongly reduce seed-dispersal distance.

The effect of fruit removal and passage through the digestive tract of frugivorous birds on seed germination has been mostly studied in species that swallow the whole fruit without mandibulating (“gulpers”), and defecate or regurgitate seeds without pulp away from the maternal plant. Functional groups with other fruit-handling methods, while often quantitatively important in removing fruits, are presumed to provide lower quality seed dispersal due to their tendency to damage seeds with the beak or discard seeds with pulp still attached under the maternal plant. We conducted a series of experiments with five bird species that mandibulate fruits with the beak before swallowing (“mashers”). They were fed with fruits of one to five plant species to test the effect of handling on their germination. We compared germination probabilities and times of seeds defecated or dropped from the bill with seeds with pulp removed by hand. Overall, bird processed seeds germinated in equal proportions than manually extracted seeds (69.9 vs 70.2%, respectively). However, depending on the bird-fruit species pair considered, the proportion and germination time of seeds processed by masher birds were equal to or less than those of manually extracted seeds. Most of the retrieved seeds processed by these birds were defecated (94%), and a large percentage of them germinated (70.3%), which confirms that they are important for the seed dispersal process. Our results provide new insights on aspects of the qualitative component of seed dispersal by masher birds. We discuss the possible implications of these findings on seed dispersal in the rest of the Neotropical region.

The species composition of local communities varies in space, and its similarity generally decreases with increasing geographic distance between communities, a phenomenon known as distance decay of similarity. It is, however, not known how changes in local species composition affect ecological processes, that is, whether they lead to differences in the local composition of species' functional roles. We studied eight seed-dispersal networks along the South American Andes and compared them with regard to their species composition and their composition of functional roles. We tested (1) if changes in bird species composition lead to changes in the composition of bird functional roles, and (2) if the similarity in species composition and functional-role composition decreased with increasing geographic distance between the networks. We also used cluster analysis to (3) identify bird species with similar roles across all networks based on the similarity in the plants they consume, (i) considering only the species identity of the plants and (ii) considering the functional traits of the plants. Despite strong changes in species composition, the networks along the Andes showed similar composition of functional roles. (1) Changes in species composition generally did not lead to changes in the composition of functional roles. (2) Similarity in species composition, but not functional-role composition, decreased with increasing geographic distance between the networks. (3) The cluster analysis considering the functional traits of plants identified bird species with similar functional roles across all networks. The similarity in functional roles despite the high species turnover suggests that the ecological process of seed dispersal is organized similarly along the Andes, with similar functional roles fulfilled locally by different sets of species. The high species turnover, relative to functional turnover, also indicates that a large number of bird species are needed to maintain the seed-dispersal process along the Andes. Fil: Dehling, D. Matthias. University of Canterbury; Nueva Zelanda Fil: Peralta, Guadalupe. University of Canterbury; Nueva Zelanda Fil: Bender, Irene Maria Antoinetta. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Böhning Gaese, Katrin. Goethe Universitat Frankfurt; Alemania Fil: Muñoz, Marcia C.. Universidad de la Salle; Colombia Fil: Neuschulz, Eike Lena. Senckenberg Biodiversität Und Klima Forschungszentrum; Alemania Fil: Quitián, Marta. Senckenberg Biodiversität Und Klima Forschungszentrum; Alemania Fil: Saavedra, Francisco. Universidad Mayor de San Andrés; Bolivia Fil: Santillán, Vinicio. Senckenberg Biodiversität Und Klima Forschungszentrum; Alemania Fil: Schleuning, Matthias. Senckenberg Biodiversität Und Klima Forschungszentrum; Alemania Fil: Stouffer, Daniel B.. University of Canterbury; Nueva Zelanda

The delivery of ecosystem services, such as biotic pollination is a benefit that nature provides us. Pollinators increase the quantity, quality and stability of crops for food production. Previous works show that proximity to natural habitats increases crop production through the delivery of pollination services. However, similar researches in subtropical regions is largely lacking. In this study we evaluated the role of linear forest fragments (LFFs) on the provision of biotic pollination service to soybean crops (Glycine max) and explored whether this service changes with increasing distance to LFFs in subtropical dry Chaco (Argentina). In three agricultural farms and testing two soybean varieties, we covered plots of 0.75 m2 with soybean plants and compared them with equally sized open plots. Plots were placed near (60 m) and far (600 m) from LFFs. We found that plants from the open treatment produced 32% more pods, 41% more seeds and had 42% higher yield (kg/ha) than plants from the covered plots. The difference between open and covered plots in seeds and yield did not change significantly with the distance to LFFs, but the number of pods, contrary to what we expected, was higher far from LFFs. Our findings highlight the possible impact of pollinators on soybean yield in both varieties tested here; but the proximity to LFFs was not directly related to a larger difference in production. Observed patterns are explained by edge effects and competition between soybean plants and trees near LFFs, combined with an underestimation of the distance from the natural hives to which honeybees can efficiently exploit the crops. In this subtropical region, soybean expansion is the most important driver of land cover change and this study represents a first step towards a better understanding of the functioning of these remnants of natural areas within the agricultural land in the region of dry Chaco forests. Fil: Zelaya, Patricia Viviana. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Chacoff, Natacha Paola. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina Fil: Aragón, Myriam Roxana. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina

Models of territorial behaviour predict a reduction in territory size when food availability and competitive pressure increase. Moreover, body size can play an important role in territorial defence. The Torrent Duck (Merganetta armata) is a river specialist that exhibits year-round territorial behaviour and long-term pair bonds. Food availability measured as biomass of invertebrates per unit area, territory and body size of Torrent Ducks were studied in the Andes in Argentina to test predictions of territoriality models. The availability of aquatic invertebrates decreased with latitude, while territory size increased. As expected, territory size of Torrent Ducks showed a negative relationship with the availability of aquatic invertebrates, a major food source for Torrent Ducks. Larger males and females paired together and occupied territories with greater food availability. Body size may be important for both males and females for the successful acquisition and defence of territories, especially during the non-breeding season when the contest winner acquires or maintains the territory and the mate. Our results suggest that Torrent Duck specialisation on fast-flowing mountain rivers leads to year-round territoriality in both sexes, a positive correlation between territorial defence and body size, and territory size proportional to food availability and population density. Fil: Ippi, Silvina Graciela. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Cerón, Gerardo. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Alvarez Guerrero, Leandro Manuel. Asociación para la Conservación y el Estudio de la Naturaleza; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Aráoz, Rodrigo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Jujuy. Universidad Nacional de Jujuy. Centro de Investigaciones y Transferencia de Jujuy; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina

Habitat loss is the primary cause of local extinctions. Yet, there is considerable uncertainty regarding how fast species respond to habitat loss, and how time-delayed responses vary in space. We focused on the Argentine Dry Chaco (c. 32 million ha), a global deforestation hotspot, and tested for time-delayed response of bird and mammal communities to landscape transformation. We quantified the magnitude of extinction debt by modelling contemporary species richness as a function of either contemporary or past (2000 and 1985) landscape patterns. We then used these models to map communities' extinction debt. We found strong evidence for an extinction debt: landscape structure from 2000 explained contemporary species richness of birds and mammals better than contemporary and 1985 landscapes. This suggests time-delayed responses between 10 and 25 years. Extinction debt was especially strong for forest specialists. Projecting our models across the Chaco highlighted areas where future local extinctions due to unpaid extinction debt are likely. Areas recently converted to agriculture had highest extinction debt, regardless of the post-conversion land use. Few local extinctions were predicted in areas with remaining larger forest patches. Synthesis and applications. The evidence for an unpaid extinction debt in the Argentine Dry Chaco provides a substantial window of opportunity for averting local biodiversity losses. However, this window may close rapidly if conservation activities such as habitat restoration are not implemented swiftly. Our extinction debt maps highlight areas where such conservation activities should be implemented. Fil: Semper Pascual, Asunción. Universität zu Berlin; Alemania Fil: Macchi, Leandro. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universität zu Berlin; Alemania Fil: Sabatini, Francesco Maria. Universität zu Berlin; Alemania Fil: Decarre, Julieta. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Recursos Biológicos; Argentina Fil: Baumann, Matthias. Universität zu Berlin; Alemania Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Gomez Valencia, Bibiana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Mastrangelo, Matias Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata; Argentina Fil: Kuemmerle, Tobias. Universität zu Berlin; Alemania

Social monogamy with genetic polygamy is a frequent mating system in birds. In Passeriformes, extra-pair paternity (EPP) was reported in 86% of the studied species, with high variation in occurrence and frequency within and between species. In the highly diverse Neotropical region, the genetic mating system is known for only 26 bird species. We present the first molecular data on the genetic breeding system of the Ringed Warbling-finch Poospiza torquata, a socially monogamous species of the tanagers family (Thraupidae) that inhabits arid and semi-arid regions of South America. We obtained data from 92 nestlings belonging to 35 nests during three consecutive breeding seasons (2008-2011). Paternity assignments were made using five microsatellites developed for other bird species, and calculated using CERVUS v. 3.0. We found that extra-pair males sired 20.65% of the offspring in 42.86% of the broods. The EPP level in this species was found to be close to the average level in Thraupidae, with reported values ranging between 8-50% and 15-63% for nestlings and broods with EPP, respectively. This wide interspecific variation points to the ecological factors as being very important in facilitating EPP among Thraupidae species. Fil: Sánchez, Rocío. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Xuereb, Amanda. University of Toronto; Canadá Fil: Lougheed, Stephen. Queens University; Canadá

[Aim] Biogeographical comparisons of interaction networks help to elucidate differences in ecological communities and ecosystem functioning at large scales. Neotropical ecosystems have higher diversity and a different composition of frugivores and fleshy-fruited plants compared with Afrotropical systems, but a lack of intercontinental comparisons limits understanding of (a) whether plant–frugivore networks are structured in a similar manner, and (b) whether the same species traits define the roles of animals across continents., [Location] Afrotropics and Neotropics., [Time period] 1977-2015., [Taxa] Fleshy-fruited plants and frugivorous vertebrates., [Methods] We compiled a dataset comprising 17 Afrotropical and 48 Neotropical weighted seed-dispersal networks quantifying frugivory interactions between 1,091 fleshy-fruited plant and 665 animal species, comprising in total 8,251 interaction links between plants and animals. In addition, we compiled information on the body mass of animals and their degree of frugivory. We compared four standard network-level metrics related to interaction diversity and specialization, accounting for differences related to sampling effort and network location. Furthermore, we tested whether animal traits (body mass, degree of frugivory) differed between continents, whether these traits were related to the network roles of species and whether these relationships varied between continents., [Results] We found significant structural differences in networks between continents. Overall, Neotropical networks were less nested and more specialized than Afrotropical networks. At the species level, a higher body mass and degree of frugivory were associated with an increasing diversity of plant partners. Specialization of frugivores increased with the degree of frugivory, but only in the Neotropics., [Main conclusions] Our findings show that Afrotropical networks have a greater overlap in plant partners among vertebrate frugivores than the more diverse networks in the Neotropics that are characterized by a greater niche partitioning. Hence, the loss of frugivore species could have stronger impacts on ecosystem functioning in the more specialized Neotropical communities compared with the more generalized Afrotropical communities., We thank Beth A. Kaplin and Norbert J. Cordeiro for their guidance and support for P.J.D., who received a travel grant by The Center for Tropical Studies and Conservation (CTEC). L.C. and I.G. were supported by the Robert Bosch Foundation. D.M.D. (DE 2754/1‐1), F.S. (HE 3041/20‐1), M.Q., V.S., E.L.N. (Research Unit 823‐825), and K.B.G., M.S. and M.G.R.V. (FOR 1246) thank the German Research Foundation (DFG) for funding. F.A.F.J. acknowledges funding by a CAPES scholarship, N.F. and D.G.S. by the Robert Bosch Foundation, M.G., C.E., A.P. and M.A.P. by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP 2010/52315‐7; 2015/15172‐7; 2016/18355‐8) and Conselho Nacional de Desenvolvimento Científico (CNPq), M.C.M. by Doctoral Fellowships from COLCIENCIAS and Rufford, M.S.S. by Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and FONCyT (PICT2013‐2759 and PICT2016‐0608), P.G.B. by CONICET (PIP 2014‐592) and FONCyT (PICT 2013‐1280), R.A.R. by a Doctoral Fellowship from CONICET, R.H. and S.T. (IF/00441/2013) and M.C. (SFRH/BD/96050/2013) by Fundação para a Ciência e Tecnologia, Portugal, and A.T. (CGL2013‐44386‐P) and D.G. (CGL2015‐68963‐C2‐2‐R) by the Spanish government. T.

In visually driven seed dispersal mutualisms, natural selection should promote plant strategies that maximize fruit visibility to dispersers. Plants might increase seed dispersal profitability by increasing conspicuousness of fruit display, understood as a plant strategy to maximize fruit detectability by seed dispersers. The role of different plant traits in fruit choice and consumption by seed dispersers has been broadly studied. However, there is no clear evidence about the importance of the traits that increase conspicuousness of fruit display. Because strategies to maximize conspicuousness of fruit display are diverse, and usually are expected to be costly, we would expect that individual plant species will produce an efficient combination of traits. We explored this prediction with 62 fleshy fruited plant species of a subtropical Andean forest (Southern Yungas), and using a large dataset of fruit consumption by birds (4476 records). Conspicuousness of fruit display was characterized by both fruit and plant traits including chromatic contrast, size, exposure, aggregation and crop size of fruits. We also considered phylogenetic effects on phenotypic variation. Fruit consumption was explained by fruit chromatic contrast depending on fruit crop size. These traits revealed low phylogenetic effects, with the exception of four plant clades at different levels in the phylogenetic tree. Negative correlations between pairs of traits support our assumption that fruit display traits are costly, suggesting natural selection favours parsimonious evolutionary pathways. Plant species seem to rely on conspicuousness of fruit display by a combination of traits that might minimize costs of fruit display. This appears adaptively relevant to improve communication with mutualistic animals, to increase fruit consumption in a community context and, ultimately, to enhance the profitability of seed dispersal. A lay summary is available for this article. Fil: Ordano, Mariano Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina. Fundación Miguel Lillo; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Lomascolo, Silvia Beatriz. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Chacoff, Natacha Paola. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Sanchez, Mariano Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Puerto Iguazú; Argentina Fil: Nuñez Montellano, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentina Fil: Jiménez, Julieta. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Ruggera, Román Alberto. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentina Fil: Valoy, Mariana. Fundación Miguel Lillo; Argentina

Most fleshy-fruited plants establish strong local interactions with a few fruit-eating species across their distribution range, which can differ among sites and have a major impact for the plant population dynamics. In turn, human disturbances alter both the original animal assemblage with which plants interact and the outcome of the mutualistic interaction. Negative consequences of human disturbances can be weakened when different seed dispersers exert similar effects on plant populations, being functionally equivalent. To understand the consequences of variability in seed dispersers on the recruitment of a long-lived tree species, I assessed changes in the assemblages of avian dispersers of Podocarpus parlatorei in subtropical Andean cloud-forests, and how these changes affect the outcome of the interaction at different spatial scales. The seed dispersal effectiveness (SDE) concept, defined as the likelihood of a seed removed by a fruit-eating bird to be dispersed to a suitable site for seed survival and germination, provides the framework to compare the contributions of different birds to seed dispersal. I compared the SDE in two old-growth forests dominated by P. parlatorei and a human disturbed forest, and in the main habitat types of these sites. In all sites, highest SDE values were provided by "gulpers" that swallow the whole fleshy cone ("fruit"), predominantly Elaenia and Turdus species. SDE was highest in forest edges and secondary forests, and negligible in other habitats. Equivalence in SDE was relatively low both within and between forest sites. Human forest disturbance modified the functional equivalence, the generalization in mutualistic interactions and the strength of SDE. Secondary forests showed the higher SDE and the greater richness of dispersers high in SDE; as a consequence, the ecological equivalence increased in the most suitable habitat for recruitment. This could lead to greater resilience of plant populations to local extinctions of dispersers, and allows the recovery of human disturbed forests. This study shows that in the replacement of functional equivalent species, the outcomes of the interactions are strongly affected by disperser abundance and habitat use, at the expense of dispersers' trait redundancy on plant population dynamics and community structure. Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina

Seed-eating birds in temperate deserts must cope with great variation in the availability of their food resources. We studied the trophic ecology of Ringed Warbling-Finches (Poospiza torquata) in semi-arid scrublands of the Monte Desert, Argentina. We assessed seasonality in the availability of seed and in the consumption of arthropods and seeds at a regional scale, and evaluated the composition of the granivorous component of the diet and the seed dietary breadth. Ringed Warbling-Finches had a granivorous–insectivorous diet consistinglargely of arthropods in summer and seeds and arthropods in winter. The granivorous component of the diet consisted mainly of grass seeds, but with low breadth of the winter seed diet. To deal with seasonal variation in the availability of food resources, Ringed Warbling-Finches switched opportunistically between different resources, exploiting alternating seasonal patterns of food abundance. This seasonal switching is a wellestablished strategy in the behaviour of the species and was observed in all Ringed Warbling-Finch populations studied across the Monte Desert. Our results show the flexibility of foraging strategies of Ringed Warbling-Finches, an opportunist species that adjusts their relative consumption of seeds and arthropods in response to the spatial and temporal variations in these food resources. Fil: Sánchez, Rocío. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The White-fronted Woodpecker (Melanerpes cactorum) drills wells in living branches and trunks of trees and shrubs to feed on sap flows, providing an energy-rich food resource for other bird species diverse in ecological attributes and taxonomic affinities. The aim of this study was to explore the avian assemblage that consumes sap from sap wells drilled by the White-fronted Woodpecker in 4 regions of Argentina distributed along an aridity gradient (precipitation and temperature), reaching from humid forest of the Chaco in the north to scrublands and open forest of the Monte in the south. We classified sap-feeding species according to the importance of nectar in their diet (specialist, facultative, or occasional nectarivores) and their efficiency in assimilation of sucrose (the main sugar in sap). We also compared the proportion of observed sap-feeding species with diversity of potential sap-feeding birds along the geographical aridity gradient. Forty-six bird species were recorded feeding at sap wells drilled by the White-fronted Woodpecker. Proportion of sap-feeding species was similar along the aridity gradient, and the type of diet and sucrase activity were not associated with the geographical aridity gradient. However, the proportion of occasional nectarivores with a low rate of sucrose assimilation was higher in Arid Monte (the most arid region) than in regions of lower aridity. Sap-feeding species could supplement their diets with sap, in varying degrees, during periods of scarcity of food resources, and White-fronted Woodpeckers through their sap wells could contribute to the persistence of this assemblage of sap-feeding bird species. Nevertheless, sap consumption by sapfeeding birds depends ultimately on the physiological and behavioral characteristics of each species. Fil: Nuñez Montellano, Maria Gabriela. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Bodrati, Alejandro. Proyecto Selva de Pino Paraná; Argentina Fil: Salvador, Sergio A.. No especifíca

En la ecorregión Pampa de América del Sur, la sustitución de los ecosistemas seminaturales por agroecosistemas es una de las principales causas de pérdida de biodiversidad. La intensificación agrícola ha llevado a la casi total desaparición de la vegetación nativa de los humedales salinos y al declive de los ensambles de aves asociados. Se eligieron relictos de humedales salinos y sus hábitats circundantes modificados para explorar las diferencias y similitudes en la estructura de los ensambles de aves que habitan desde hábitats naturales relictos a nuevos ecosistemas agrícolas, en el centro de Argentina. El área de estudio está incluida en la región Pampa, en la parte conocida como Pampa Interior Plana de América del Sur. Específicamente, el área se encuentra en el departamento Marcos Juárez, al sudeste de la provincia de Córdoba, Argentina. Se identificaron ocho hábitats con composiciones y estructuras florísticas muy contrastantes y se realizaron tres campañas de conteo de aves durante un ciclo anual: enero-febrero, julio-agosto y octubre de 2013. En cada uno de los hábitats se establecieron estaciones de conteo de aves de radio fijo. Se registraron 60 especies de aves en total pertenecientes a 21 familias. Los resultados en términos de diversidad de especies y gremios tróficos indican que las especies de los ensambles de aves se asocian diferencialmente con diferentes comunidades de vegetación. Los valores más altos de los números de la riqueza y de los gremios de aves fueron registrados en los ambientes naturales de vegetación estructuralmente complejos. Los hábitats más modificados por actividades humanas (estructuralmente más simples) fueron más pobres en sus ensambles de aves. Llegamos a la conclusión de que la promoción y conservación de los parches de paisaje de los humedales salinos naturales (mezcla de pastizales y matorrales) como la fisonomía principal de la vegetación debería tener una alta prioridad en las agendas futuras destinadas a la conservación de la integridad y la diversidad de las poblaciones de aves de los pocos hábitats naturales remanentes de la ecorregión Pampa. In the Pampa ecoregion of South America, the replacement of semi-natural ecosystems by agroecosystems is a major cause of biodiversity decline. Agricultural intensification has led to the almost total disappearance of pristine wetland vegetation and the decline of bird assemblages. Relicts of saline wetlands and modified surrounding habitats were chosen to explore differences and similarities in the assemblage structure of birds inhabiting the habitat spectrum from natural relicts to new agricultural ecosystems, in central Argentina. The study area is in the Pampa region, in the sector known as Flat Inland Pampa. Specifically, it is located in Marcos Juárez department, southeastern Córdoba province, Argentina. We identified eight habitats with contrasting floristic compositions and structures and three bird count surveys were conducted during an annual cycle: January-February, July-August, and October 2013. Fixed-radius survey stations were established in each habitat. Sixty bird species, from 21 families, were recorded. The results in terms of species diversity and trophic guilds indicate that bird species assemblages are associated differentially with different vegetation communities. The highest values of bird richness and guild numbers were recorded in structurally complex natural vegetation environments. The structurally simpler habitats modified by human activities were poorer in their bird assemblages. We conclude that the promotion and conservation of the patchiness of the landscape of natural saline wetlands (mixed grassland-shrubland) as the main physiognomies of the vegetation should have high priority in future agendas for conserving the integrity and diversity of bird populations of the remaining natural habitats in the Pampa ecoregion. Fil: Brandolin, Pablo Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Biología Agrícola; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Cantero, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Biología Agrícola; Argentina

Fruit selection, i.e., the consumption of fruits disproportionately to their availability, results from the interaction between diet preferences and ecological factors that modify them. We assessed the importance of functional fruit traits to explain fruit selection by birds in Andean subtropical forests, taking into account temporal variation in trait distribution in the assembly of available fruits. During 2 yr, we measured the abundance of ripe fruits and their consumption by birds in a 6-ha plot during 11 bimonthly samplings, and we used 17 phenological, morphological, and nutritional traits to characterize fruits selected by four bird species. Fruit selection was pervasive year-round, highly variable over time and across bird species. Fruit species were selected over time periods shorter than their ripening phenology, and the selection of fruits with particular traits was specific to the fruit-eating species. Maximization in pulp reward per consumed fruit seems to be the main driving force behind fruit selection, indicating that birds select fruits with traits that directly affect net energy gain. Our results can be interpreted in a framework of a hierarchy of foraging decisions, under which the spatiotemporal context of the fruiting environment modifies the relative intake rates of a particular fruit, while the ability to discriminate fruit contents becomes increasingly important on a smaller dimension. We show that fruit-selection properties are contingent on specific fruit traits and particular spatiotemporal conditions, which modify the structure of mutualistic interactions. Resumen La seleccion de frutos es el resultado de la interaccion entre las preferencias de dieta de las aves y los factores ecologicos que las modifican. En este estudio, evaluamos la importancia de rasgos funcionales de frutos para explicar la seleccion de frutos por aves, teniendo en cuenta la variacion temporal en la distribucion de los rasgos en el ensamblaje de frutos disponibles en el ambiente. Medimos la abundancia de frutos maduros y su consumo por aves en 11 muestreos bimensuales en una parcela de 6 hectareas. Utilizamos 17 rasgos fenologicos, morfologicos y nutricionales para caracterizar funcionalmente los frutos seleccionados por las cuatro especies de frugivoros mas abundantes. La seleccion de frutos fue generalizada a lo largo del ano, y muy variable en el tiempo y entre especies de aves. Las especies de frutos fueron seleccionadas por periodos de tiempo mas cortos que el de su fenologia de maduracion, y la seleccion de frutos con rasgos particulares fue especifica de cada especie de ave. La principal fuerza detras de la seleccion de frutos parece ser la maximizacion de la recompensa en pulpa por fruto consumido, sugiriendo que las aves seleccionan frutos con rasgos que afectan directamente su ganancia neta de energia. Nuestros resultados pueden entenderse en una jerarquia de decisiones de forrajeo, segun la cual el contexto espaciotemporal del ambiente fructificante modifica la tasa relativa de ingesta de una especie de fruto, y en una dimension menor, prevalece la capacidad de discriminar el contenido de los frutos. Mostramos que las propiedades del proceso de seleccion de frutos son contingentes de determinados caracteres de los frutos y de condiciones particulares tales como la presencia de otras especies en fruto, las cuales modifican la estructura de las interacciones mutualistas.

Woodpeckers feed primarily on insects, larvae and other arthropods; however, several members of this family include plant products in their diets, such as sap. Among them, the genera Sphyrapicus and Melanerpes include the most species that specialize in sap consumption. In semiarid forests of Argentina, sap is an important food item in the diet of the White-fronted Woodpecker, Melanerpes cactorum. The aim of this study is to investigate why White-fronted Woodpeckers only consume sap from certain plants while avoiding other available plants of the same species and explore seasonality of their plant selection. We expected that combinations of plant traits (i.e. sugars concentration of sap, sap flow intensity, plant size, plant health and plant microhabitat), rather than one particular trait, determine which tree they select for sap feeding in different seasons. We examined five plant species: Sarcotoxicum salicifolium, Prosopis ruscifolia, Ziziphus mistol, Aspidosperma quebracho-blanco and Stetsonia coryne that were used most frequently for sap consumption and were consumed in all seasons by ten groups of White-fronted Woodpecker in semiarid Chaco, Argentina. Plants selected by White-fronted Woodpeckers for sap consumption were mainly larger plants that yield high sugar concentration. Of the plant species we studied, individual plant selection in all seasons was more evident in those plant species that constitute an important part of their diet (i.e. Prosopis ruscifolia and Stetsonia coryne). The selection of plants offering a greater reward in sap quality strongly suggests that the White-fronted Woodpecker maximizes food energy intake as a response to the seasonality that characterizes semiarid climates of temperate regions and conditions of food resources availability. Our results show that large trees are selected as sap trees by White-fronted Woodpecker, therefore, we recommend activities that promote retention of large trees in Chaco region. Fil: Nuñez Montellano, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina

Determining the response of birds to local habitat characteristics and landscape structure is essential to understanding habitat selection and its consequences for the distribution of species. This study identified the influence of environmental factors as determinants of the waterbird assemblage composition in 39 wetlands in the Pampas of central Argentina. Multivariate analysis allowed the identification of environmental factors affecting the use of habitat by waterbird species, whose variable numbers were explained by local and landscape environmental factors. Interspecific variation in responses to changes in environmental factors shows that habitat selection occurs at a species-specific level, although species with similar ecological requirements tend to respond similarly to environmental heterogeneity. Plovers and flamingos were mostly associated with high salinity and the presence of a muddy shoreline and temporary ponds; ducks, herons and ibises were associated with vegetation abundance and decrease in salinity; piscivores and carnivorous species were associated with water depth. The small degree of overlap of habitat requirements between some species suggests a high level of specialization within waterbird assemblages. This knowledge can be used for the design of appropriate conservation and management strategies in central Argentina, where the alarming loss of wetlands requires management strategies that ensure the permanence of the greatest diversity of waterbirds. Fil: Brandolin, Pablo Germán. Universidad Nacional de Rio Cuarto. Facultad de Agronomia y Veterinaria. Departamento de Biología Agrícola. Cátedra de Botanica Sistematica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Blendinger, Pedro Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Laboratorio de Investigaciones Ecológicas de las Yungas; Argentina

Sap is a resource of high energy content that is usually inaccessible to birds, although woodpeckers have the ability to drill into living trees to obtain sap. Because spatial patterns of resource availability influence avian abundance, we explored how spatial patterns of sap availability determine the spatial distribution of two sap-feeding species in the semiarid Chaco of Argentina. We studied the White-fronted Woodpecker (Melanerpes cactorum), which obtains sap by drilling holes into tree trunks, and the Glittering-bellied Emerald (Chlorostilbon aureoventris), which can obtain sap only from active woodpecker holes; 12 other bird species also exploited the sap flows from holes drilled by White-fronted Woodpeckers. The abundance of tree species used for sap feeding did not explain the spatial patterns of territorial groups of White-fronted Woodpeckers. However, within each territory, the abundance of Woodpeckers was centred on a single tree from which sap was obtained. The abundance of the Emeralds was strongly associated with the availability of trees with active sap-holes. During the dry season, sap is a major component in the diet of White-fronted Woodpeckers and Glittering-bellied Emeralds. However, the spatial distribution of these two consumers in relation to the availability of sap was species-specific. This species-specific response was closely related to the ecology and life history of each species. The abundance of woodpeckers could be determined by local mechanisms, such as location of a single sap tree in their small territories, whereas non-territorial hummingbirds would be able to track sap wells at a larger scale than the territory of a single territorial group of Woodpeckers. Our results show the importance of spatial analysis in identifying the ecological determinant of habitat selection and niche differentiation within species. © 2011 Royal Australasian Ornithologists Union. Fil: Macchi, Leandro. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Laboratorio de Investigaciones Ecológicas de las Yungas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Laboratorio de Investigaciones Ecológicas de las Yungas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina Fil: Nuñez Montellano, Maria Gabriela. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Laboratorio de Investigaciones Ecológicas de las Yungas; Argentina. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina

Interactions between resource and consumer species are organized in ecological networks. Species interactions in these networks are influenced by the functional traits of the interacting partners, but the generality of trait-based interaction rules and the relationship between functional traits and a species’ specialization on specific interaction partners are not yet understood. Here we combine data on eight interaction networks between fleshy-fruited plants and frugivorous birds sampled across the tropical and subtropical Andean range. We test which combinations of morphological plant and animal traits determine trait matching between resource and consumer species in these networks. In addition, we test which of the morphological traits influence functional specialization of plant and bird species. In a meta-analysis across network-specific fourth-corner analyses, we found that plant–animal trait pairs related to size matching (fruit size–beak size) and avian foraging behavior (plant height–wing shape and crop mass–body mass) were positively related in these networks. The degree of functional specialization on specific interaction partners was positively related to crop mass in plants and to the pointedness of the wing in birds. Our findings show that morphological trait matching between fleshy-fruited plants and frugivorous birds is a general phenomenon in plant–frugivore networks across the Andes and that specific plant and bird traits can be used to approximate the degree of functional specialization. These insights into the generality of interaction rules are the base for predictions of species interactions in ecological networks, for instance in novel communities in the future, and can be applied to identify plant and animal species that fulfill specialized functional roles in ecological communities. Fil: Bender, Irene Maria Antoinetta. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Martin-Luther-Universität Halle-Wittenberg; Alemania. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania. Universitätsbund Halle – Jena – Leipzig. German Centre for Integrative Biodiversity Research; Alemania Fil: Kissling, W. Daniel. University of Amsterdam; Países Bajos Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Böhning Gaese, Katrin. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania. Universitätsbund Halle – Jena – Leipzig. German Centre for Integrative Biodiversity Research; Alemania. Goethe Universitat Frankfurt; Alemania Fil: Hensen, Isabell. Martin-Luther-Universität Halle-Wittenberg; Alemania. Universitätsbund Halle – Jena – Leipzig. German Centre for Integrative Biodiversity Research; Alemania Fil: Kühn, Ingolf. Universitätsbund Halle – Jena – Leipzig. German Centre for Integrative Biodiversity Research; Alemania. Martin-Luther-Universität Halle-Wittenberg; Alemania. Helmholtz-Zentrum für Umweltforschung; Alemania Fil: Muñoz, Marcia C.. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania. Goethe Universitat Frankfurt; Alemania Fil: Neuschulz, Eike Lena. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania Fil: Nowak, Larissa. Goethe Universitat Frankfurt; Alemania. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania Fil: Quitián, Marta. Goethe Universitat Frankfurt; Alemania. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania Fil: Saavedra, Francisco. Universidad Mayor de San Andrés; Bolivia Fil: Santillán, Vinicio. Goethe Universitat Frankfurt; Alemania. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania Fil: Töpfer, Till. Zoologisches Forschungsmuseum Alexander Koenig; Alemania Fil: Wiegand, Thorsten. Universitätsbund Halle – Jena – Leipzig. German Centre for Integrative Biodiversity Research; Alemania. Helmholtz-Zentrum für Umweltforschung; Alemania Fil: Dehling, Matthias. University of Canterbury; Nueva Zelanda. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania Fil: Schleuning, Matthias. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania

Several species of woodpecker drill holes in living trees to feed on flows of sap. We describe sap-holes drilled by the White-fronted Woodpecker (Melanerpes cactorum) on plant species in semi-arid woodlands of northern Argentina, and examine, for the first time, attributes of the plants that may help to explain the configuration and geometry of sap-holes made by a species of woodpecker. Sap-holes vary among plant species, mostly in size and shape, and in their arrangement and location on tree branches. Moreover, patterning of sap-hole are closely similar in structurally similar species, showing foraging decisions of White-fronted Woodpeckers associated with plant structure-types at a supra-specific level. In large trees, sap-holes were small, round and arranged in rows on branches or trunks of large diameter, whereas in smaller Prosopis trees, sap-holes were rectangular and located on branches of small diameter. In other species of tree and shrub sap-holes were large and irregular, and on branches of intermediate diameter. The size of holes was positively correlated with substrate diameter for small and intermediate branches of a given group of species, but was independent of diameter in tree species with holes on the trunk. The switch between sap-consumption strategies related to attributes of trees opens the possibility that White-fronted Woodpeckers drill sap-holes trying to maximise sap-harvesting. Fil: Nuñez Montellano, Maria Gabriela. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales E Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales E Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

In most dietary studies of fruit-eating birds, sampling methods consist of direct observations of foraging and fecal sample analyses, and the consumption of resource types is measured as the percent of occurrence in diet samples, or as counts (frequency) of ingested items. Since these measures are usually biased towards the overestimation of small and abundant resources, the amount of ingested mass is a more accurate measure of the crude energy and nutrients provided by a given food source. In this study, we use direct observations of foraging behavior to describe the diet of four frugivorous-insectivorous bird species during the breeding season in Southern Yungas forests, and we compare the number of ingested items and ingested dry mass as measures of fruit and arthropod consumption. In terms of ingested food dry mass, fruit consumption represented over 95% of the diet of the four bird species. The estimated proportion of fruit in the diet differed significantly among methods in three bird species. The comparison of two methods to quantify food consumption by birds allowed us to determine that, when gross amount of ingested matter is considered, the proportion of arthropods in the diet of frugivorous-insectivorous species is much smaller than previously reported. Our study suggests that the use of food dry mass is more appropriate than methods based on item counting to determine the importance of food items in the diet, since it avoids overestimation of resources which contribute comparatively little to the total energy and nutrients ingested. The comparison of these methods highlights the importance of using more reliable measurements of the contribution of different types of food to characterize the diet of frugivorous-insectivorous bird species. Fil: Nazaro, María Gabriela. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina

The stability and dynamics of multispecies interactions often rely on a small core of species. We examine whether the Yellow-striped Brush-Finch (Atlapetes citrinellus), the only species of bird endemic to the Argentinean Yungas, is a core species for seed dispersal. Of 30 species of fleshy fruit consumed, 16 were dispersed through endozoochory. The Yellow-striped Brush-Finch mostly used the ‘cut or mash’ method of handling fruit, in which reasonably large seeds (>0.04 g) were discarded or swallowed equally. Medium-sized and small seeds were more often swallowed than discarded. Although the fruits consumed were mostly understorey species, there was no difference in the consumption of fruit from forest understorey or canopy when total fruit abundance in vertical strata was considered. By using interaction network metrics, we determined that the role of Yellow-striped Brush-Finches in seed dispersal during the rainy season was more important at higher altitudes and in the southern sector of its distribution. Our findings support the idea that the Yellow-striped Brush-Finch must be considered a core seed-disperser of understorey and canopy fruits. Use of network metrics is an effective way to assess the importance of individual species in a network, allowing restoration and conservation efforts to be focussed on environments in which these species occur. Fil: Ruggera, Román Alberto. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gomez, Maria Daniela. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Studies of the foraging behaviour of birds allow exploration of the mechanisms that structure species assemblages. The major objective of this study was to describe relationships among various components of foraging behaviour and whether changes in those relationships reflected seasonal changes in assemblage structure of birds from an arid scrubland of the Monte Desert, Argentina. Foraging behaviour was described in terms of attack manoeuvres, food substrate (i.e. substrate from which food taken), foraging site (i.e. the substrate and height where birds foraged), and plant species used. Between-species differences in these three components of foraging behaviour were interrelated, the association being strongest between foraging sites and food substrates. During the non-breeding season, foraging sites and food substrates differentiated species. The most important changes between seasons were related to the arrival in summer of aerial-foraging tyrant flycatchers, a functional group absent during the non-breeding season. Foraging sites explained most of the differences among species groups, suggesting that habitat heterogeneity and structural complexity of vegetation are important environmental variables that determine the avian assemblage structure. Moreover, temporal changes in food availability, mediated by strong seasonality in climate, were important factors that were correlated with compositional and structural variability in functional groups of birds (i.e. granivores-insectivores, surface insectivores and aerial insectivores). Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Laboratorio de Investigaciones Ecológicas de las Yungas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina