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Author |
Gauthier, G., Doyle, F. I., Gilg, O., Menyushina, I. E., Morrison, R. I. G., Ovsyanikov, N., Pokrovsky, I., Reid, D. G., Sokolov, A. and Therrien, J.-F. |
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Abstract |
Arctic predatory birds are a diverse group that includes raptors (falcons, hawks, eagles and owls) and tundra seabirds (jaegers and gulls). Many species show irruptive behaviour, which makes it difficult to assess population trends and possible range expansion or contraction. A few species such as the peregrine falcon in North America and Russia, the short-eared owl in Nunavut, the great skua in Greenland and the parasitic jaeger in Greenland and the Russian Far East have nonetheless shown recent range expansion and/or population increase. In contrast, there is evidence that populations of the gyrfalcon in the Yukon North Slope and some parts of Russia, the snowy owl in Europe and the Russian Far East and the pomarine jaeger in the Russian Far East may have recently declined. Population cycles of lemmings and voles have a strong impact on the local abundance and reproduction of most avian predators. However, this varies according to the degree of specialisation of predatory birds on small mammals and among sites. Snowy owls showed the strongest response to fluctuations in small mammal abundance. Rough-legged hawks and long-tailed jaegers also showed a strong response at some sites but not at others such as in northern Yukon and in some parts of Siberia. Intensive studies on Bylot Island showed that avian predators consume a very high proportion of the annual lemming production and could regulate the abundance of collared lemmings during the snow-free period. Satellite-tracking of snowy owls in North America allowed us to measure the scale of their annual movements. Female owls moved over long distances between consecutive breeding seasons (from 18 to 2224 km) and always settled and bred in areas where lemmings were abundant. Most owls attempted to breed every year in far apart areas, which confirms that when small mammals crash in an area, owls will not forego breeding but will rather move over long distances to find suitable breeding conditions (i.e. high small mammal populations). During winter, most female owls remained in the Arctic (north of 55° of latitude) but, surprisingly, they extensively used the sea ice for up to 101 days in the Eastern Canadian Arctic. Birds of prey are top predators and could act as indicator species for the tundra ecosystem. Climate induced changes such as increase in shrub abundance, shift in the distribution of small mammal species or collapse of lemming population cycles in some areas could negatively impact the populations of several birds of prey. An additional source of concern in some areas is illegal killing or trapping for trade. The new links revealed by our study between the terrestrial and marine ecosystems also suggest that some populations of predators such as the snowy owl may be supported by the marine ecosystem in winter. Therefore, a broader, cross-ecosystem perspective may be required when assessing the status or threats faced by these predators. Monitoring of avian predators should not only provide information on the status of their populations but also on the health of the whole Arctic ecosystem
– In: Gauthier, G. and Berteaux, D. (eds.),
Final synthesis report. Centre d’études nordiques, Université Laval, pp. 62-75. |
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