Breeding Biology of the Golden-Faced Tyrannulet (Zimmerius chrysops) in Venezuela

Abstract

Abstract We present the first detailed information on the breeding biology of the Golden-faced Tyrannulet (Zimmerius chrysops). Information was gathered from 96 nests in Yacambu National Park, Venezuela during the 2002 to 2008 breeding seasons. The enclosed nest was similar to descriptions of nests of other species in the genus. Eggs were laid on alternate days with mean (± SE) clutch size of 1.98 ± 0.02 (n = 45) and fresh weight of 1.616 ± 0.020 g (n = 48). Only the female incubated and the incubation period averaged 16.9 ± 0.3 days (n = 10). Nest attentiveness (% time on the nest) averaged 66.0 ± 1.6% (n = 40) and increased from early to mid- and late-incubation. Incubation behavior yielded an average 24-hr egg temperature of 34.88 ± 0.45° C (n = 7 nests, 43 days). The nestling growth rate constant for body mass (k = 0.285 ± 0.011) was slow even for tropical tyrannids. The nestling period for nests where exact hatch and fledging days were observed ranged from 17 to 19 days with an average of...