Atlas Maps Movements of Banded Birds

Like sending winged messages in bottles, Canadians have been banding birds and keeping records of where and when they're found for almost a century. Although fewer than five per cent of the 50 million birds banded in North America since 1905 have ever been encountered, these efforts have yielded a surprising amount of information about the routes and destinations of many species.

This summer Environment Canada's Canadian Wildlife Service (CWS) published a 400-page report summarizing, for the first time, results for all the small landbirds banded or encountered in Canada. The publication, Canadian Atlas of Bird Banding, Volume 1: Doves, Cuckoos and Hummingbirds through Passerines, 1921-1995, was compiled over the past 25 years by an amateur bander in Guelph, Ontario, and by CWS scientists in Ottawa and Saskatchewan.

Environment Canada coordinates the Canadian arm of the North American Bird Banding Program, which sees approximately 220 000 birds banded in Canada each year. Some 900 licensed banders, including a large number of volunteers, contribute to the effort by netting or trapping birds, attaching numbered identification bands to their legs, and recording data such as age, sex, location, date and state of health. If a banded bird is encountered—that is, spotted, captured or found dead—more information is taken. The results are useful not only to banders and researchers interested in bird ecology, movement, productivity, survival and migratory patterns, but also to wildlife managers and conservationists interested in knowing more about the winter destinations and migration routes of Canada's birds.

The atlas provides a full account for each species with at least one record of an individual moving more than 100 kilometres—in this volume, 133 of the 227 species of small landbirds banded in Canada. Each account discusses movement patterns, recaps previously published analyses, and summarizes statistics on encounter rates and mean distances moved. It also provides fascinating details about some individual encounters, such as the White-Throated Sparrow that flew 673 kilometres in a single day, and the tiny Bank Swallow that was banded in Saskatchewan and found years later in Bolivia, nearly 8 000 kilometres away.

Special maps show movement between banding and encounter locations, as well as the frequency of banding by species and geographic location—the latter never having been published before. Although independent analyses of the movement of some species of banded birds have been carried out in the past—particularly for birds of economic importance, such as waterfowl, or species that cause agricultural damage—most of the results for rarely encountered species appear for the first time in this atlas.

Comparisons among more frequently encountered species reveal geographic differences in movement patterns that are often consistent across many species. For example, many landbirds migrate south toward the Gulf of Mexico, but take very different routes to get there. Generally speaking, landbirds west of the Rockies head due south along the Pacific coast each fall, while those from the prairies and northern British Columbia head southeast. Maritimes landbirds head southwest, parallel to the Atlantic coast, some of them crossing paths with individuals from western populations over the Great Lakes. Birds in Ontario and Quebec also tend to head due south.

One of the many applications of this information was illustrated earlier this year, when CWS was asked to provide expert advice on the potential for migrant birds to carry the West Nile Virus from New York City into Canada. Although the atlas shows that over 200 species migrate through the area, migration dates show that they head north before mosquito season each spring, making it unlikely that they would pick up anything en route. While the virus could be caught on their fall migration south, it is uncertain whether birds can carry the virus more than a week—let alone over the winter. In addition to focusing surveillance efforts along the Atlantic coast, banding studies revealed that the greatest threat likely occurs when young birds disperse prior to fall migration.

Over the next several years, CWS also hopes to publish banding atlases for raptors, waterbirds, seabirds and shorebirds. The first volume of the Canadian Atlas of Bird Banding is available in hard copy and on the web at http://www.cws-scf.ec.gc.ca/publications/spec/atlas_e.cfm.

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