DESCRIPTION OF THE NEST, EGGS, AND BREEDING BEHAVIOR OF THE ENDANGERED PALE-HEADED BRUSH-FINCH (ATLAPETES PALLIDICEPS) IN ECUADOR

Resumen

The Pale-headed Brush-Finch (Atlapetes pallidiceps) is a critically endangered endemic bird species that is restricted to a single valley in southern Ecuador. We present the first description of the nest, eggs, breeding behavior, and juvenal plumage of this species. Seventy-two percent of nests (n = 18) were placed on thin overhanging branches 1–3 m above the ground, directly beneath the top layer of foliage in dense thickets. Nesting material consisted of various proportions of grass, twigs, and bamboo stalks and leaves. Clutch sizes ranged from 1–3 eggs (n = 22), and ≥55% of nests (n = 18) were parasitized by Shiny Cowbirds (Molothrus bonariensis). The background color of eggs was buffish white to bluish, and they were spotted and blotched with diffuse brown markings. Mean egg size was 24 × 17.8 mm. Fledgling plumage differed from adult plumage and had some characteristics similar to the adult White-winged Brush-Finch (Atlapetes leucopterus). Females alone incubated the eggs, and both parents fed the offspring. Incubation and nestling times were 12–14 days each. Fledglings of the Pale-headed Brush-Finch were led for several weeks after fledging. No pair initiated a second clutch after a successful first one (n = 16), but we observed second and third clutches after nest failure had occurred. Prolonged postfledging care is assumed to prevent multiple broods of the Pale-headed Brush- Finch during one season.