CONICET | Buscador de Institutos y Recursos Humanos

The view that migratory paths are ruledby inherited cue-responses would suggest that it takes many generations forselection to effect large-scale changes in migratory behavior. Barn Swallow isa common breeder throughout much of North America, and the vast majority ofthem migrate to Central and South America for the northern winter. This speciesbegan breeding in Argentina in the 1980?s in an area that had formally beennear the edge of the bird?s common wintering range, and the populationcontinues to grow and spread from there. Population genetic data, as well asobservations in breeding colonies, indicate that individuals of North Americanorigin are still recruiting to the Argentinean breeding population. Thelong-distance migration patterns of the North American birds raise a veryinteresting question: Do the swallows breeding in Argentina have a migratoryroute and destination like their North American ancestors, migrating to NorthAmerica (and potentially even breeding there?!) in the southern winter, or dothey instead migrate like most austral migrants to northern South America forthe winter? Earlier analyses of stable isotope profiles suggested the latter,but those analyses could not rule out a North American migratorydestination. Data from geolocation loggers now conclusively demonstratethat the birds have a migratory pattern like most austral migrants: they spendthe southern winter in northern/central South America. We will discuss thepossible mechanisms that may have produced this rapid change and itsimplications for the evolution of migratory patterns in general.