Barn Swallows keep expanding their breeding range in South America

JUAN M. GRANDE; MIGUEL A. SANTILLÁN; PAULA M. OROZCO; M. SOLEDAD LIÉBANA; MARCOS M. REYES; MAXIMILIANO A. GALMES; JOAQUÍN CEREGHETI

EMU

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2015 vol. 115 p. 256 - 260

0158-4197

Abstract North American Barn Swallows (Hirundo rustica) traditionally wintered in South America. In the 1980?s a small breeding population was found in coastal Argentina and since then it has largely expanded its range in the country. Our aims here were to examine the north-western limits of the species breeding range in Argentina, and to analyse factors that may determine nesting site selection by the species. We surveyed and characterized culverts and bridges below roads, the most frequently used breeding substrate by the species in the country, in a 15,000 km2 area in northern La Pampa Province, Central Argentina. We found 51 nests in 39 culverts and bridges sparsely distributed through most of the surveyed area. We also found 16 nests outside that area in central Buenos Aires and La Pampa provinces. Occupied culverts were taller and more frequently in the surroundings of wetlands than unoccupied culverts. Most nests were in agricultural landscapes with just a few in Caldén (Prosopis caldenia) forests. Our results confirm that the breeding range of the species in South America has expanded by about a third, but there is still a large tract of suitable habitat for the species mostly to the north, suggesting that additional range expansion of the species is expectable in coming years. For the first time, our study documents the expansion of this common species within South America and speculates on the underlying reasons.