Predators of bird nests in the Atlantic forest of Argentina and Paraguay

Predation is the major cause of avian nest failure, and an important source of  natural selection on life history traits and reproductive behavior. However, little is known about the identity of nest predators in much of the world, including the Neotropics. To identify some of the nest predators exerting selection pressure on birds of the subtropical Atlantic forest, we present observations of animals depredating bird nests in Argentina and Paraguay. We recorded depredations (destruction or removal of eggs or nestlings) at 33 nests of 25 species of birds, confirming as predators ten species of birds (Squirrel Cuckoo Piaya cayana, White-eared Puffbird Nystalus chacuru, Toco Toucan Ramphastos toco, Red-breasted Toucan Ramphastos dicolorus, Saffron Toucanet Pteroglossus baillonii, Chestnut-eared Aracari Pteroglossus castanotis, Planalto Woodcreeper Dendrocolaptes platyrostris, White-throated Woodcreeper Xiphocolaptes albicollis, Buff-browed Foliage-gleaner Syndactyla rufosuperciliata, and Plush-crested Jay Cyanocorax chrysops) and two species of medium-sized mammals (White-eared Opossum Didelphis albiventris and Crab-eating Fox Cerdocyon thous), and inferring two additional mammal species (Black Capuchin Monkey Sapajus nigritus and Southern Tigrina Leopardus guttulus). Fifty-five percent of these nests were depredated by toucans or aracaris (Ramphastidae), which destroyed eggs and nestlings at cup-, closed- and cavity-nests. Red-breasted Toucans destroyed nests 1.6?22 m high, in habitats ranging from primary forest to a backyard. Mammals and jays depredated nests from ground-level to midstory, whereas woodcreepers and aracaris depredated nests from the midstory to canopy. We did not record snakes at any bird nests, in strong contrast to studies from other Neotropical forests. Further studies should examine trade-offs among nest concealment, physical protection, and parental defense behavior as means of reducing nest predation, and use camera traps to quantify nest predation rates by predator species.Fil: Cockle, Kristina Louise. Proyecto Selva de Pino Paraná; Argentina. University of British Columbia; Canadá. 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. State University of Louisiana; Estados UnidosFil: Bodrati, Alejandro. Proyecto Selva de Pino Paraná; ArgentinaFil: Lammertink, J. Martjan. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentina. Cornell University; Estados Unidos. Proyecto Selva de Pino Paraná; ArgentinaFil: Bonaparte, Eugenia Bianca. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Proyecto Selva de Pino Paraná; ArgentinaFil: Ferreyra, Carlos. Proyecto Selva de Pino Paraná; ArgentinaFil: Di Sallo, Facundo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Proyecto Selva de Pino Paraná; Argentin

Distribution, Abundance and Habitat Selection by Breeding Yellow-billed Terns ( Sternula superciliaris

The distribution and abundance of Yellow-billed Terns (Sternula superciliaris), Large-billed Terns (Phaetusa simplex) and Black Skimmers (Rynchops niger) were estimated, and the effects of habitat features on site occupancy by colonies of these three species nesting in the Anavilhanas Archipelago, Amazonas, Brazil, were examined. Individuals were recorded on beaches during the 2008 and 2009 breeding seasons, with 26 (2008) and 30 (2009) potential nesting beaches (sites) surveyed. In both years, one site included 28% of all the Yellow-billed Terns, while two sites included 65% of all the Large-billed Terns. Site occupancy, the probability that a site is occupied (range Ψ), was moderate to low for all three species, but higher for Yellow-billed Terns (0.58-0.63) than for Large-billed Terns (0.40-0.50) and Black Skimmers (0.23-0.54). Yellow-billed and Large-billed terns and Black Skimmers generally nested on larger beaches on islands that had little vegetative cover and that were exposed to open water, remote from river margins, distant from other islands and closer to large colonies of the same species. Abundance estimates (individuals per breeding season in the archipelago ± SE) in 2009 varied considerably among species (Yellow-billed Terns: 192 individuals ± 1; Large-billed Terns: 80 ± 1; Black Skimmer: 31 ± 1). These results suggest that habitat features that influence breeding site use by Yellow-billed and Large-billed terns and Black Skimmers include physical and vegetation characteristics as well as social attraction. While the probability of site occupancy increased with measures related to beach size and geographical isolation, closeness to large colonies indicates the relevance of social interactions for these species and, as such, the importance of large areas for the occurrence of their colonies