No abstract

ABSTRACT. Identification of the predators of bird nests is essential to test ecological and evolutionary hypotheses and to make practical management decisions. A variety of nest monitoring devices have been proposed but many remain difficult to set up in the field. The aim of this study was to test camera traps as a potential tool to study predation of natural nests in a tropical rainforest environment. Specifically, we registered the predators, assessed their size range, and we compared the use of one and two cameras per nest. Of 122 nests from 24 bird species, 45 (37%) were depredated, and the cameras recorded the predator species in 29 of the total of depredated nests (64%). We identified predators in eight of 16 depredated nests (50%) in which we used one camera trap per nest, and we identified predators in 21 of 29 depredated nests (72%) when we used two camera traps per nest. The predators included six species of birds and six species of mammals, with body masses varying from 20 g to 16.5 kg. Causes for 10 of the 16 detection failures were identified and are discussed. These results suggest that camera traps are viable tools to investigate nest predation in a tropical rainforest area.

No abstract

Identification of the predators of bird nests is essential to test ecological and evolutionary hypotheses and to make practical management decisions. A variety of nest monitoring devices have been proposed but many remain difficult to set up in the field. The aim of this study was to test camera traps as a potential tool to study predation of natural nests in a tropical rainforest environment. Specifically, we registered the predators, assessed their size range, and we compared the use of one and two cameras per nest. Of 122 nests from 24 bird species, 45 (37%) were depredated, and the cameras recorded the predator species in 29 of the total of depredated nests (64%). We identified predators in eight of 16 depredated nests (50%) in which we used one camera trap per nest, and we identified predators in 21 of 29 depredated nests (72%) when we used two camera traps per nest. The predators included six species of birds and six species of mammals, with body masses varying from 20 g to 16.5 kg. Causes for 10 of the 16 detection failures were identified and are discussed. These results suggest that camera traps are viable tools to investigate nest predation in a tropical rainforest area.

Nest predation is one of the main causes of bird mortality, and the development of nest anti-predatory defenses can mold many aspects of bird evolution. Here we report that bats can attack nests in incubation and nestling stages in the Atlantic Forest, Brazil. Although other types of interactions between birds and bats have been reported, including predation of adult individuals and the co-occurrence in cavity nests, bats may have been underestimated as nest predators. The combination of flying and olfactory skills makes bats functionally different compared to other predators, opening new perspectives on the interpretation of nesting-birds anti-predatory strategies. They represented 8% of all recorded potential predations in the bird community studied, being more important than reptiles, and were responsible for 33% of nest losses for at least one bird species. Our data suggest the potential for nest depredation by bats to be an important selective factor in shaping anti-predatory strategies of nesting birds. Then, the use of devices capable to detect bats will be essential for reliable interpretations of birds nest defense mechanisms in future works.

The Thamnophilidae are one of the most speciose Neotropical bird families, yet aspects of their natural history remain poorly documented. Here we provide information on breeding phenology, the length of incubation and nestling periods, parental care, and nesting success of the Star-throated Antwren, Rhopias gularis, an Atlantic Forest endemic. The data are discussed in light of life history theories. We found 27 active nests during two breeding seasons (2013/2014 and 2014/2015) at Carlos Botelho State Park in southeastern Brazil. Nesting activities were observed from September to January. Incubation and nestling periods lasted 16.8 ± 0.6 and 11.0 ± 0.86 days, respectively, as with most other antbirds. Males and females shared equally in incubation and nestling provisioning. The small clutch size of two eggs is that most commonly found in tropical birds and is hypothesized to have evolved due to increased nest predation rates. However, our data was not consistent with this hypothesis as the nest survival probability was high (57%). This is one of only a handful of studies that provide comprehensive information on the breeding biology of a Thamnophilid species in undisturbed habitat.Keywords: breeding phenology, life history, nesting behavior, nesting success, parental care.Reprodução da choquinha-de-garganta-pintada, Rhopias gularis (Aves: Thamnophilidae), uma espécie endêmica da Mata Atlântica Resumo A Família Thamnophilidae compreende as diversas espécies de chocas e papa-formigas e compõem um dos maiores grupos de aves neotropicais. Apesar do elevado número de espécies, aspectos da história natural permanecem pouco documentados. No presente estudo são fornecidas informações sobre fenologia reprodutiva, duração dos períodos de incubação e permanência dos filhotes no ninho, cuidado parental e sucesso reprodutivo da choquinha-de-garganta-pintada, Rhopias gularis, endêmica da Mata Atlântica, enfocando teorias de história de vida. Foram encontrados 27 ninhos ativos durante duas temporadas reprodutivas (2013/2014 e 2014/2015) no Parque Estadual Carlos Botelho, no sudeste do Brasil. Atividades de nidificação foram observadas de setembro a janeiro. Períodos de incubação e permanência dos filhotes nos ninhos duraram 16.8 ± 0.6 e 11.0 ± 0.86 dias, respectivamente, sendo similares aos de outras chocas e papa-formigas. Machos e fêmeas dividiram as funções de incubação e alimentação dos ninhegos em taxas similares. As ninhadas de dois ovos seguem o padrão mais comum para Passseriformes tropicais, mas os dados apresentados não se mostraram consistentes com a hipótese de que a evolução de ninhadas menores está relacionada às altas taxa de predação de ninhos nesta região, uma vez que foi observada alta probabilidade de sobrevivência (57%). O presente estudo é um dos poucos a proporcionar informações abrangentes sobre a biologia reprodutiva de um Thamnophilidae em uma área preservada.Palavras-chave: fenologia reprodutiva, história de vida, comportamento de nidificação, sucesso reprodutivo, cuidado parental.

Several hypotheses have been proposed to account for the function of eggshell pigmentation. One predicts that patterns of colour and markings provide camouflage against visually oriented nest predators. However, the effectiveness of any anti‐predatory function of eggshell colour may be reduced if predators can use the nests per se as foraging cues (nest‐crypsis hypothesis). Here, we tested whether eggshell pigmentation, and a set of concurrent variables, could explain nest predation in natural nests of the Atlantic Forest endemic Blue Manakin Chiroxiphia caudata containing plasticine eggs. Nests were continuously monitored for predator identification using infra‐red camera traps, and we considered the nest‐crypsis hypothesis by testing the premise that if predators can use nests as visual cues, they would be recorded checking empty nests at rates similar to those containing eggs. Six bird species were identified as visually oriented predators of nest contents, and predation frequencies were low and not influenced by eggshell colour. Empty nests and nests containing eggs were visited by predators at similar frequencies, independently of eggshell colour, which provided the first direct support for the nest‐crypsis hypothesis. It suggests that for this tropical forest, open‐nesting passerine, selective forces driving nest concealment and nest camouflage may be stronger than selection for eggshell colour variation.

No abstract