Nest-site characteristics affect daily nest-survival rates of Northern Aplomado Falcons (Falco femoralis septentrionalis)

Abstract

We modeled daily nest-survival rates (DSR) of a reintroduced population of Northern Aplomado Falcons (Falco femoralis septentrionalis; hereafter "falcons") in southern Texas. Although falcons have nested in the region since 1995, the factors influencing reproductive success are not understood. Nest sites were classified into nest-type groups using a cluster analysis based on nest substrate and nest builder. Using an information-theoretic approach, we compared relative effects of nest age, study area, nest-type group, and physical nest-site characteristics. Our results were similar to previous studies of passerine nesting ecology, in that DSR varied throughout the nesting cycle: it was constant during incubation, declined at hatching and the early nestling phase, and increased through the remainder of the nestling phase. Nest type and nest height were important physical nest-site covariates, overhead cover was less important, and study area and nest initiation date were not influential. We note that although nest success was well correlated with simple nest-site covariates, many falcons chose poor-quality nest sites, which raises the question of whether nest-site selection by falcons is optimal in this region. © The American Ornithologists' Union, 2008.