title: Pulsed resources at tundra breeding sites affect winter irruptions at temperate latitudes of a top predator, the snowy owl.
abstract: Irruptive migration is mostly observed in species specialized on pulsed resources and is thought to be a response to unpredictable changes in food supply. We assessed two alternative hypotheses to explain the periodic winter irruptions of snowy owls Bubo scandiacus every 3-5 years in temperate North America: (a) the lack-of-food hypothesis, which states that a crash in small mammal abundance on the Arctic breeding grounds forces owls to move out of the tundra massively to search for food in winter; (b) the breeding-success hypothesis, which states that high abundance of tundra small mammals during the summer allows for high production of young, thus increasing the pool of migrants moving south the following winter. We modeled winter irruptions of snowy owls in relation to summer food resources and geographic location. Winter abundance of owls was obtained from citizen-based surveys from 1994 to 2011 and summer abundance of small mammals was collected in summer at two distant sites in Canada: Bylot Island, NU (eastern High Arctic) and Daring Lake, NWT (central Low Arctic). Winter owl abundance was positively related to prey abundance during the previous summer at both sites and tended to decrease from western to eastern temperate North America. Irruptive migration of snowy owls was therefore best explained by the breeding success hypothesis and was apparently caused by large-scale summer variations in food. Our results, combined with previous findings, suggest that the main determinants of irruptive migration may be species specific even in a guild of apparently similar species.
authors.affiliation: Département de biologie and Centre d'études nordiques, Université Laval, Sainte-Foy, QC, G1V 0A6, Canada. Audrey.robillard.2@ulaval.ca.
authors.forename: A
authors.identifier: 0000-0002-3690-7080
authors.initials: A
authors.lastname: Robillard
authors.affiliation: Département de biologie and Centre d'études nordiques, Université Laval, Sainte-Foy, QC, G1V 0A6, Canada.|Acopian Center for Conservation Learning, Hawk Mountain Sanctuary, 410 Summer Valley Road, Orwigsburg, PA, 17961, USA.
authors.forename: J F
authors.initials: JF
authors.lastname: Therrien
authors.affiliation: Département de biologie and Centre d'études nordiques, Université Laval, Sainte-Foy, QC, G1V 0A6, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Gauthier
authors.affiliation: Wildlife Division, Department of Environment and Natural Resources, Government of the Northwest Territories, Yellowknife, NT, X1A 2R3, Canada.
authors.forename: K M
authors.initials: KM
authors.lastname: Clark
authors.affiliation: Département de biologie, chimie et géographie and Centre d'études nordiques, Université du Québec à Rimouski, Rimouski, QC, G5L 3A1, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Bêty
mesh_terms: D000818:Animals; D001110:Arctic Regions; D001947:Breeding; D012621:Seasons; D020305:Strigiformes; D065929:Tundra
keywords: Bubo scandiacus; Irruptive migration; Small mammal; Wintering range; Zero-inflated negative binomial model