Biologia reprodutiva do Veste-amarela (Xanthopsar flavus, Gmelin 1788) nos Campos de Cima da Serra, Sul do Brasil

Abstract

The life history of many South American icterids is still relatively unknown. We presente detailed information on the breeding biology of a population the vulnerable Saffron-cowled blackbird in the high altitude grasslands of southern Brazil. We found 18 breeding colonies of 28 ± 25 individuals, with a positive relationship between the number of breeding pairs and colony size (y = .967x + .296; r = 0.929, P < 0.001). We collected data on 47 nests found over two breeding seasons from 2011 to 2013 in the Campos de Cima da Serra region. Breeding occurs from mid-October to late January/early February and groups move as large flocks of up to 300 individuals from March to September. Females build an open-cup nest of thick and thin grasses in emergent wetland vegetation or shrubs (mainly Eryngium horridum, Baccharis trimera and Ludwigia multinervia) at 45.12 ± 24.68 (sd) cm above the ground in three to six days (mean = 4 ± 1.26 d, n = 6). Clutch size is 3.78 ± 0.55 (sd) eggs (Range: 3 – 5), and eggs ( n= 19) measure 1.62 ± 0.09 (sd) cm by 2.18 ± 0.08 (sd). Incubation is performed by the female and lasts 12 ± 1days (n = 5). Females are most attentive during the early morning and the mid-afternoon. Males help feed nestlings but make less trips/hr than females (U30 = 74, P = 0.04) and spend up to 60% of their time guarding the nest. There was a positive relationship between nestling age and the number of trips/hr by parents (r 2 = 0.395, P < 0.001). We found discrepancies between the breeding season of X. flavus in the Campos de Cima da Serra region and other parts of Southern South America, which may be related to resource availability and habitat quality. The clutch sizeand nest characteristics were similar to those found for this species in Uruguay and Argentina. Although it has been extirpated from the majority of its original distribution, X. flavus still reproduces in relatively large groups in north eastern Rio Grande do Sul and conservation efforts should be intensified to assure its continued survival in Brazil.