Biologia reprodutiva e comportamento cooperativo em ninhos de Cyspsnagra Hirundinacea

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

White-rumped Tanager (Cypsnagra hirundinacea) is a cooperative breeding species, which helpers are offspring of earlier breeding seasons. This species occurs in open areas of the Cerrado (Neotropical savanna). The first chapter of this dissertation presents a description of several aspects of C. hirundinacea reproductive biology, including reproductive period, nest, eggs, nestlings, incubation and nestling periods, parental care and cooperative breeding. The second chapter aims to estimate survival probability from total nests period, and separately during incubation and nestling period as a function of temporal and environmental variables. Nest searches and monitoring were conducted at Estação Ecológica de Águas Emendadas (ESECAE), Distrito Federal, Brazil, from 2002 to 2007. Sixty-four nests were found during these years. The breeding period started in mid August and ended in the first half of December. Nests, eggs and nestlings characteristics are similar to the ones reported for other tanagers. Clutch size varied from one to three eggs and incubation period lasted 16 0.3 days. Incubation is asynchronous and only the female incubated eggs, while male and helpers only guarded the nest from a short distance. Nestling period was 12.1 0.5 days. The breeding pair and the helpers fed the nestlings and defended the nest during this phase. Nestlings growth rates of body mass and wing were higher at nests with helpers than at nests without helpers. In addition, at the end of the period, nestlings from helped nests were morphometric more similar to adults than nestlings from unhelped nests. Food delivery rate per nestling was higher in helped nests, and both breeding female and male had lower food delivery rates at these nests. Thus, helper presence at the nest increased nestling body condition, which might have affected their survival and breeding pair fitness. Fifty-eight nests were active, from which 32.7% were successful, 56.9% depredated (apparent predation), and 10.4% abandoned. Nest predation was the main cause of nest losses, with an average of 54.3% among years. Mayfields nest survival probability was 26.7%, similar to that one found to other passerine birds in Cerrado and in other tropical areas. Using model selection of daily survival probabilities in program MARK, different effects of temporal and environmental variables were found during all nest periods (incubation, nestling and total). This study suggests that nest survival probability decreased through the breeding season and during nest age, being important predictive variables. The variables year, nest height, and nest distance to the nearest road had little support in the models considered and the variable helper presence at the nest had no effect on daily survival rates.

ASSUNTO(S)

história de vida program mark cerrado reprodução cooperativa biologia reprodutiva breeding biology programa mark life history cypsnagra hirundinacea white-rumped tanager (cypsnagra hirundinacea) sucesso reprodutivo ecologia cooperative breeding, reproductive success cerrado (neotropical savanna)

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