Trends in the abundance and distribution of wild birds

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Bird populations have been widely recognized as reliable indicators of biodiversity. Birds occur in large numbers and in a wide range of habitats all over the world, and are sensitive to environmental change. It is believed that declines in bird populations are linked to degradation of the environment, and that a decline in bird population signals a likely decline of other species for similar reasons.

Trends in abundance and distribution of selected species, including trends in bird populations, are an indicator for assessing progress towards the 2010 Biodiversity Target. The Wild Bird Index, in use in Europe and currently being expanded to a global scale, is used as an indicator of the general health of the wider environment and will serve as input to the 2010 Biodiversity Target.

Monitoring studies show that common bird species are in decline in many parts of the world. It has been demonstrated that “[t]he status of bird species show a continuing deterioration across all biomes over the last two decades.” In particular, experts have warned that migratory bird populations are steadily deteriorating around the world.

Trends in the status of Ontario’s bird populations were recently reported in the Atlas of the Breeding Birds in Ontario, 2001-2005. Released in 2007 and based on data collected by 3,000 volunteers who spent over 150,000 hours in the field, the atlas reveals that population trends appear generally positive for some bird populations, including many forest birds such as thrushes and warblers, and large species such as the Canada goose, sandhill crane, wild turkey and several species of swan. Some species that were previously in decline such as the peregrine falcon, bald eagle and merlin have rebounded.

However, the atlas also reveals that trends for many other species in Ontario show steep declines. In particular, populations of grassland, wetland and scrubland birds and birds that feed on flying insects, including the common nighthawk, bobolink, whip-poor-will, chimney swift and several species of swallow, have declined significantly in the last two decades.


This is an article from the 2007/08 Annual Report to the Legislature from the Environmental Commissioner of Ontario. Click here for more information on the official document and its release.

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