Nesting success of understory forest birds in central Panama

Abstract

Greater nest predation in tropical than temperate birds has been hypothesized to be a primary selective force generating latitudinal differences in avian life history traits. Few extensive data sets, however, have been available from tropical forests to compare with data from temperate forests. To increase the amount of empirical information available for addressing issues related to the evolution of life history traits of tropical birds, we measured the nesting success of understory birds in lowland forest of central Panama. We found and monitored the fates of 696 nests of 71 species over two breeding seasons. Daily nest predation rates for the ten species for which we obtained the largest samples ranged from 1.6 to 8.3%, equivalent to a loss of 43 to 92% of nests. These values overlapped extensively the range of daily predation rates experienced by ecologically similar species in North America. Proportion of nests fledging young, estimated with the Mayfield method, was significantly lower in tropical (range: 8 to 57%) than temperate (27 to 60%) species. Nesting success in Panama varied among years, however, being greater in 1996 than 1997. In 1996, nesting success was similar to that of species breeding in forest fragments of midwestern North America. When compared with success of nests in large, contiguous forest tracts of North America, however, tropical avian nesting success was consistently lower by approximately 23%. We conclude that nesting success in central Panama may be poor in most breeding seasons, but also may be punctuated by occasional years of relatively exceptional success, a possibility heretofore unappreciated because of a general paucity of data from the tropics. Furthermore, our results indicate substantial variation in levels of nesting success among species, and almost no variation in clutch size. Such large interspecific variation, as well as potentially large annual variation, in nesting success does not support the hypothesis that uniformly low levels of nesting success select for small tropical clutch sizes.

Habitat fragmentation reduces nest survival in an Afrotropical bird community in a biodiversity hotspot

“…Finally, our results demonstrate, on the basis of the largest sample of species and nests yet included in such an analysis, that multiple environmental factors contribute to reduced nest survival within a tropical understory bird community in a fragmented landscape. In our study system the predominant cause of nest failure was nest predation, which is consistent with patterns of nest failure observed elsewhere in the tropics (18)(19)(20) and in temperate regions (23,24). Over the course of the study we observed a diverse community of predators, comprising raptors, snakes, rodents, and ants, preying on eggs and young.…”

“…Previous studies comparing avian nest survivorship between fragmented and intact forest in the tropics have either used artificial nests and eggs (12,13), which unfortunately often poorly mimic the fate of real nests and eggs (14-16); or if real nests have been found, have lumped species together in the analysis because of small sample sizes (17), which can be misleading because nest survivorship can vary locally among tropical bird species (18)(19)(20)(21). Similarly, the few studies in the tropics that have examined edge effects on nest survival using real nests and eggs have been either single-species studies (22) or have pooled nests across species (17).…”

Striped-tailed Yellow-finch nesting success in abandoned mining pits from central Brazilian cerrado

“…Such cases, however, apparently represent extreme values due to their discrepancies comparing to other studies in the cerrado region. Nest survival rates we found for Stripe-tailed Yellow-finch are also similar to other emberizid breeding Robinson et al 2000), as well as altered habitats in Venezuela (29%; Ramo and Busto 1984). Predation was the major cause of nests failure in our study, responsible for 89% of nest losses.…”

Biologia reprodutiva de Tyrannus savana (Aves, Tyrannidae) em cerrado do Brasil Central

“…Portanto, apenas ninhos encontrados em construção ou com postura incompleta, e que puderam ser monitorados até a eclosão, foram considerados para essa estimativa. Definimos o tempo de permanência dos ninhegos no ninho pelo intervalo entre a eclosão do primeiro ovo e a saída do último filhote (Robinson et al 2000). Determinamos o período reprodutivo da espécie na região através da atividade dos ninhos.…”