Robillard A, Therrien J F, Gauthier G, Clark K M, Bêty J
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.
Oecologia. 2016 Jun;181(2):423-33. doi: 10.1007/s00442-016-3588-3. Epub 2016 Feb 26.
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.
爆发性迁徙主要在依赖脉冲式资源的物种中观察到，被认为是对食物供应不可预测变化的一种反应。我们评估了两种替代假说，以解释在北美洲温带地区雪鸮（Bubo scandiacus）每3至5年出现一次的周期性冬季爆发性迁徙：（a）食物短缺假说，该假说认为北极繁殖地小型哺乳动物数量的急剧下降迫使雪鸮在冬季大量离开苔原去寻找食物；（b）繁殖成功假说，该假说认为夏季苔原小型哺乳动物数量众多使得幼崽数量增加，从而增加了次年冬季南迁的迁徙者数量。我们建立了雪鸮冬季爆发性迁徙与夏季食物资源和地理位置之间的模型。雪鸮冬季数量来自1994年至2011年基于公民的调查，小型哺乳动物夏季数量是在加拿大两个相距遥远的地点夏季收集的：努纳武特地区的拜洛特岛（北极东部高地）和西北地区的大胆湖（北极中部低地）。两个地点雪鸮冬季数量与前一年夏季的猎物数量呈正相关，并且从北美洲温带地区西部到东部呈下降趋势。因此，雪鸮的爆发性迁徙最好用繁殖成功假说来解释，显然是由食物的大规模夏季变化引起的。我们的结果与之前的研究结果相结合，表明即使在一个明显相似的物种群体中，爆发性迁徙的主要决定因素可能也因物种而异。
