CONICET | Buscador de Institutos y Recursos Humanos

The Saffron-cowled Blackbird (Xanthopsar flavus) is an endemic passerine of the temperate grasslands of southern South America categorized as vulnerable by IUCN. Four small and disjoint populations remained in the southwest of Brazil and Uruguay; southeast of Paraguay and northeast of Argentina. In Argentina the species has been classified as critically endangered due to a sharp decline in its populations during the last decade, decreasing its numbers from 1500 to only 600. Regular reproductive sites are unprotected. In 2015 we initiated a project to detect and protect the colonies to increase reproductive success of both populations from Entre Rios and Corrientes located in two endangered IBA (AR177 IBA and AR143). Due to the low nest survival in the colonies, we designed physical protections methods to protect them from medium sized predators. Two different kinds of devices were developed, one to protect the nests during incubation and the other for the nest in nestlings stage. During the 2015-2018 breeding season we installed shade cloths enclosures in 70 incubating nests, and metal mesh enclosures in 84 nests during nestling stage. Adult acceptance of the enclosures and nest predators activity were monitored with camera traps. The proportion of nests that were not depredated during incubation was significantly higher in protected nests (77%; χ2=26.25, p-value=8.43x10-6) than in unprotected nests (42%). In nests containing chicks, the nesting success was also significantly higher in protected nests (80%; χ2=25.56, p-value= 1.17x10-5) than in unprotected nests (42%). In this study, we describe these simple and cheap device used to increase the nesting success of Saffron-cowled Blackbirds colonies prone to high predation risk, which could also be applied to other species of grassland birds that nest on or near the ground.

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