What determines the timing and duration of the nesting season for a tropical dry forest bird, the White-throated Magpie-Jay (Calocitta formosa)?

Abstract

ABSTRACT The factors affecting the timing of nesting in tropical birds remain poorly understood. We investigated the phenology of White-throated Magpie-Jay (Calocitta formosa) nesting in the dry forest of northwest Costa Rica, a region characterized by a severe 5-month dry season followed by a very rainy wet season. We examined whether nesting was associated with climate, diet, risk of parasite infection to nestlings, risk of nest predation, and opportunity to re-nest. Groups of White-throated Magpie-Jays nested repeatedly, initiating nests over a 7-month period that spanned the transition from the dry to early wet season. The diet of adults and the composition of food fed to broods varied seasonally in parallel with changes in vegetation condition and climate associated with the transition from dry to wet season. Fledgling transition to nutritional independence occurred exclusively in the wet season when caterpillars and other arthropods were a large component of the diet. The timing of groups’ last nest...