Long-Distance Range Expansion and Rapid Adjustment of Migration in a Newly Established Population of Barn Swallows Breeding in Argentina.
When bird populations spread, long-distance pioneering populations are often backfilled by a more slowly advancing front [1-3]. The Barn Swallow Hirundo rustica, a globally distributed passerine [4, 5], expanded its breeding range an exceptional 7,000 km when it began breeding 35 years ago in its regular wintering range in Argentina [6], subsequently expanding over 500 km from its starting point [7-11]. Trans-hemispheric breeding attempts have occurred previously in related swallows [12-14], but only this colonization has lasted. Comparative studies of birds show a remarkable diversity in patterns of change in migratory habits [15-21], and these Argentine-breeding swallows might retain ancestral patterns, breeding in Argentina but returning to North America for the austral winter. Feather isotopes from these birds are consistent with the alternative possibility that they migrate no farther than northern South America [22]. Because isotopic patterns cannot definitively distinguish these alternatives, we pursued a solar geolocator study [23, 24] to do so. Data from nine tagged birds show conclusively that Barn Swallows breeding in Argentina have rapidly changed their movements to migrate no farther north in austral winter than northern South America. The phenology of the annual cycles of molt, migration, and breeding for these Argentine-breeding swallows have all shifted by about 6 months, and we suggest that stimulatory day lengths and the proliferation of nesting substrates facilitated their colonization.
Department of Ecology and Evolutionary Biology, Museum of Vertebrates and Laboratory of Ornithology, Cornell University, Corson Hall, Ithaca, NY 14853, USA. Electronic address: dww4@cornell.edu.
David W
DW
Winkler
Instituto de Bio y Geociencias del Noroeste Argentino (IBIGEO)-CONICET, Av. 9 de Julio 14, Rosario de Lerma 4405, Salta, Argentina.
Facundo A
FA
Gandoy
Instituto de Bio y Geociencias del Noroeste Argentino (IBIGEO)-CONICET, Av. 9 de Julio 14, Rosario de Lerma 4405, Salta, Argentina.
Juan I
JI
Areta
Department of Ecology and Evolutionary Biology, Museum of Vertebrates and Laboratory of Ornithology, Cornell University, Corson Hall, Ithaca, NY 14853, USA.
Marshall J
MJ
Iliff
Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research and Utrecht University, P.O. Box 59, 1790 AB Den Burg, Texel, the Netherlands; Department of Vertebrate Zoology, Faculty of Biology, Lomonosov Moscow State University, 119992 Moscow, Russia.
Eldar
E
Rakhimberdiev
Environment and Climate Change Canada, Wildlife and Landscape Research Directorate, 11 Innovation Boulevard, Saskatoon, SK S7N 3H5, Canada.
Kevin J
KJ
Kardynal
Environment and Climate Change Canada, Wildlife and Landscape Research Directorate, 11 Innovation Boulevard, Saskatoon, SK S7N 3H5, Canada; Department of Biology, University of Western Ontario, 1151 Richmond Street, London, ON N6A 5B7, Canada.
Keith A
KA
Hobson
D063147:Animal Distribution; D025041:Animal Migration; D000818:Animals; D001118:Argentina; D011158:Population Growth; D012098:Reproduction; D012621:Seasons; D046388:Swallows / Q000502:physiology*
Hirundinidae; bird; breeding season; human-altered habitats; migration; photoperiod; range extension; swallow