Natural history and conservation of the endangered Saffron-cowled Blackbird Xanthopsar flavus in Argentina

• Published in: Bird conservation international 1998-09, Vol.8 (3), p.255-267
• Main Authors: Fraga, Rosendo M., Casañas, Hernán, Pugnali, Germán
• Format: Article
• Language: English
• ISSN: 0959-2709; 1474-0001
• DOI: 10.1017/S095927090000191X

Based on 21,518 km of road surveys, the Argentinian range of the endangered Saffron-cowled Blackbird Xanthopsar flavus now seems confined to two small and disjunct areas in Corrientes and Entre Rios provinces, north-east Argentina. In Corrientes the species inhabits natural pastures and rice-fields; in Entre Rios agropastoral land. Estimates based on numbers of localities and flock sizes suggest a Saffron-cowled Blackbird population of 500–1,000 individuals. This blackbird is highly gregarious. Mean flock size (n = 30, non-breeding period) was 31.9 birds (range: 6–102), and was significantly larger in Entre Rios. In Corrientes foraging blackbird flocks associated mostly with the Black-and-White Monjita Xolmis dominicana, in Entre Rios with the Brown-and-Yellow Marshbird Pseudoleistes virescens. Nesting in both provinces was colonial, with up to 24 nests in a 0.43 ha plot. Nests were built in native and introduced herbaceous plants. The Shiny Cowbird Molothrus bonariensis parasitized 29.2% of the nests in one colony; its eggs and chicks are larger than those of the host. Plausible reasons for the species's extinction or decline at a local level are drainage of wetlands (south-west Buenos Aires Province) and the replacement of pastures with pine and eucalypt plantations in Corrientes. General threats include trapping for the pet trade and increased cowbird parasitism. Flocks below a minimum size may not be viable. An urgent measure of protection would be the fencing and preservation of traditional colony sites. En base a 21.518 km de censos de rutas parece que la distributión actual del amenazado Tordo Amarillo o Dragón Xanthopsar flavus en Argentina está limitada a dos pequeñas áreas disyuntas en las provincias de Corrientes y Entre Rios. En Corrientes la especie se encuentra en pasturas naturales y arroceras, mientras que en Entre Rios usa campos agrícola-ganaderos. Una estimatión basada en el número de localidades y tamaños de bandadas indicaría una población total de 500 a 1.000 individuos. El tamaño promedio de bando (n = 30, período no reproductive) fue 31,9 individuos (rango 6–102) y es significativamente mayor en Entre Rios. En Corrientes las bandadas se asocian principalmente con la Monjita Dominica Xolmis dominicana, y en Entre Rios con el Pecho Amarillo Pseudoleistes virescens. La nidificación fue colonial en ambas provincias, con una densidad de hasta 24 nidos en 0,43 ha. Los nidos se construyeron en plantas herbáceas nativas y exóticas. El Tordo