Reproductive biology and territoriality of the wedge-tailed grass-finch (Emberizoides herbicola) (Aves: Passeriformes)

Abstract

Emberizoides herbicola (Wedge-tailed Grass-finch), Emberizidae, Passeriformes, lives in various types of grasslands in South America. Its life history is poorly known and here we provide novel information on several aspects of its breeding biology, including territoriality and habitat use. We investigated it at Águas Emendadas Ecological Station, Federal District, Brazil, between 2002 and 2009. Banded E. herbicola had an average territory size of 3.9 ha (n = 6). Twenty nests were monitored every 2-4 days, of which 18 were active. The reproductive period occurred from October to March, but eggs were laid from early October to mid-November, with a peak in late October. Nests were built close to the ground and (mean height = 14.8 ± 9.0 cm, n = 17) clutch size was invariably two but ranged from one to three eggs (mean = 2 ± 0.4, n = 15). Incubation period was 14.8 ± 0.8 days (n = 2) and nestling period was 11 ± 0.6 days (n = 4). Most nests (n = 12) were built in open cerrado vegetation. Among the 18 active nests, 44.4% were successful, 38.9% were depredated and 16.7% were abandoned. Predation rate during the nestling period (85.7%) was significantly higher than during the incubation period (14.3%). Mayfield nest success rate was 42%, with a much higher survival rate during the egg period (0.881 ± 0.112) than during the nestling period (0.476 ± 0.147). Most nests (n = 12) were built in open cerrado vegetation, which may be considered the most important habitat for the species both for territory defense and nesting.