Millions of birds migrate from around the Earth to breed in the Arctic each year. A total of over 450 bird species are known to breed in Arctic and Sub Arctic areas. Of these, 395 species regularly migrate outside the Arctic and Sub Arctic, linking these regions with almost all areas of the planet (except inland Antarctica) via their migratory route. Four species migrate within the region. More than half of the world’s shorebirds and almost 80% of the world’s geese breed in the Arctic and Sub Arctic. The indices in this figure indicate an overall increase in non-migrant populations, whereas migratory populations slightly decreased (-6%). But there is no significant difference between the trends in the two groups. The decline in migratory bird populations would be more pronounced if the increasing geese shown in the previous figure were not included. As well, long-term monitoring of Arctic migrants takes place across the Earth at wintering and staging sites. Although the migratory index involves 170 species comprising 424 populations, many shorebird data from monitoring stations outside the Arctic (the majority of which are declining have not yet been included.
Unlike resident species, population sizes of migratory species can be influenced by conditions at any stage of migration with impacts only becoming apparent after monitoring at subsequent stages. Many Arctic breeding waders or shorebirds are in decline, but the reasons are not fully understood. Although changes in the Arctic, such as snow cover, humidity and increasing shrub cover may impact shorebirds, there are many other factors inside (e.g., changing distribution and extent of tundra wetlands) and outside the Arctic to consider in explaining the trends. For example, pre-nesting and egg-laying periods are major energetic bottlenecks across the entire Arctic region. Warmer temperatures in spring and summer over large parts of the Arctic tundra can be largely beneficial for shorebird populations, however, the recent observed declines are mostly attributed to threats outside the Arctic region. Changes in habitat and food availability on key stopover sites are crucial for the survival of shorebird populations.
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For the period 1970-2004. (All birds, n=190 species, 503 populations; migrants, n=170 species, 424 populations; non-migrants, n=29 species, 79 populations.)
