Nest description and nesting behavior of the rufous-capped warbler (basileuterus rufifrons)

Abstract

The breeding biology of most tropical resident bird species is little-documented, particularly for sexually monomorphic species in which sex-specific contributions to nest-building and nestling provisioning are challenging to quantify. We describe nest structure and adult behavior throughout the nesting cycle for a color-banded population of Rufous-capped Warblers (Basileuterus rufifrons), a widespread sexually monomorphic tropical resident songbird. Using focal observations of 11 nests, combined with video monitoring during the incubation and nestling periods, we provide new information on this species' nesting behavior, particularly sex-specific parental contributions to nestbuilding, incubation, and nestling care. All nests were dome-shaped structures with a side entrance constructed of grasses, twigs, and leaves, as is typical for Basileuterus warblers. Females were the primary nest-builders, although we also observed male-assisted nest-building at one nest, which is a rare behavior in wood-warblers. Females were the sole incubators, and the incubation period in this population was 13-14 days. Video recordings confirmed that males and females made equivalent contributions to nestling feeding and nest sanitation. Our study provides detailed observations of both male and female Rufous-capped Warblers during all stages of the nesting cycle, and thus improves our understanding of nesting behavior in this common yet little-studied species.