Title
Seasonal Movements of Female Snowy Owls Breeding in the Western North American Arctic
Author(s)
Doyle, Frank I.;Therrien, Jean-François;Reid, Donald G.;Gauthier, Gilles;Krebs, Charles J.
Published
2017
Publisher
Journal of Raptor Research
Abstract
Abstract The Snowy Owl (Bubo scandiacus) is a circumpolar raptor that nests in Arctic tundra. Satellite tracking of nesting Snowy Owls in Alaska and eastern Canada has allowed researchers to document the widely nomadic movements of these owls between summer and winter ranges. This study expands that knowledge for Snowy Owls in the western Canadian Arctic. Based on previous studies, we predicted that owls: (1) would not have strong fidelity to specific winter or summer ranges; (2) would travel widely in search of breeding and nonbreeding areas at which they would settle for considerable time (months); (3) would choose areas to settle based on prey concentration; and (4) would use a mix of overwintering strategies, with some staying in Arctic and boreal regions, and some migrating south. Movement patterns of four female owls captured at nesting sites on Herschel Island, Yukon Territory, Canada, supported the first two predictions. The third prediction was partly supported: some sites of summer settlement were located where prey was relatively abundant, whereas other selected sites did not appear to have enough prey for successful nesting. The latter sites may have been the best available in those areas, however. Sites of winter settlement generally overlapped regions with high abundance of snowshoe hares (Lepus americanus) or ptarmigan (Lagopus spp.), and were located in relatively open alpine, subalpine, or wetland environments, where prey were likely most accessible. Contrary to our last prediction, all four study owls settled in boreal Alaska and the northern Yukon Territory. This pattern contrasts with observations that eastern North American Snowy Owls rarely wintered in the boreal biome. This study highlights the need to better understand the habitat choices and food habits of wintering Snowy Owls in the northern boreal mountains.
The Snowy Owl (Bubo scandiacus) is a circumpolar raptor that nests in Arctic tundra. Satellite tracking of nesting Snowy Owls in Alaska and eastern Canada has allowed researchers to document the widely nomadic movements of these owls between summer and winter ranges. This study expands that knowledge for Snowy Owls in the western Canadian Arctic. Based on previous studies, we predicted that owls: (1) would not have strong fidelity to specific winter or summer ranges; (2) would travel widely in search of breeding and nonbreeding areas at which they would settle for considerable time (months); (3) would choose areas to settle based on prey concentration; and (4) would use a mix of overwintering strategies, with some staying in Arctic and boreal regions, and some migrating south. Movement patterns of four female owls captured at nesting sites on Herschel Island, Yukon Territory, Canada, supported the first two predictions. The third prediction was partly supported: some sites of summer settlement were located where prey was relatively abundant, whereas other selected sites did not appear to have enough prey for successful nesting. The latter sites may have been the best available in those areas, however. Sites of winter settlement generally overlapped regions with high abundance of snowshoe hares (Lepus americanus) or ptarmigan (Lagopus spp.), and were located in relatively open alpine, subalpine, or wetland environments, where prey were likely most accessible. Contrary to our last prediction, all four study owls settled in boreal Alaska and the northern Yukon Territory. This pattern contrasts with observations that eastern North American Snowy Owls rarely wintered in the boreal biome. This study highlights the need to better understand the habitat choices and food habits of wintering Snowy Owls in the northern boreal mountains.
Bubo scandiacus es una rapaz circumpolar que nidifica en la tundra ártica. El seguimiento satelital de individuos de B. scandiacus nidificantes en Alaska y el este de Canadá ha permitido a los investigadores documentar los movimientos ampliamente nómadas de estos búhos entre las áreas de veraneo e invernada. Este estudio completa ese conocimiento para B. scandiacus en el oeste del Ártico canadiense. En base a estudios previos, predecimos que los búhos: (1) no presentarían una fidelidad pronunciada hacia áreas específicas de veraneo e invernada; (2) viajarían ampliamente en busca de áreas reproductivas y no reproductivas en las que se establecerían durante un tiempo considerable (meses): (3) elegirían áreas para establecerse basados en la concentración de presas; y (4) utilizarían una mezcla de estrategias de invernada, con algunos individuos permaneciendo en regiones árticas y boreales y otros migrando hacia el sur. Los patrones de movimiento de cuatro hembras de B. scandiacus capturadas en lugares de nidificación en la Isla Herschel, Territorio Yukón, Canadá, apoyaron las dos primeras predicciones. La tercera predicción fue apoyada en parte: algunos lugares de establecimiento en verano estuvieron ubicados en zonas donde las presas eran relativamente abundantes, mientras que otros lugares parecieron no tener suficientes presas para una nidificación exitosa. Sin embargo, estos últimos pudieron haber sido los mejores sitios disponibles en esas áreas. Los lugares de invernada generalmente se superpusieron con regiones con una elevada abundancia de Lepus americanus y de Lagopus spp., y estuvieron ubicados en hábitats alpinos y subalpinos relativamente abiertos y en humedales, donde las presas probablemente fueron más accesibles. Contrariamente a nuestra última predicción, las cuatro hembras estudiadas se establecieron en el norte de Alaska y el norte del Territorio Yukón. Este patrón contrasta con las observaciones de que individuos de B. scandiacus de América del Norte raramente invernan en el bioma boreal. Este estudio destaca la necesidad de conocer mejor la selección de hábitat y los hábitos alimentarios de individuos de B. scandiacus invernando en el norte de las Montañas Boreales.
Keywords
Snowy Owl;Bubo scandiacus;migration;movements;North America;seasonal habitat;wintering;Yukon Territory
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