Canadian Atlas of Bird Banding

General Overview

The bulk of this atlas series consists of individual species accounts that depict movement patterns and summarize data to indicate what is available for further analysis. Although species accounts range from those reporting a single encounter to those summarizing 10000 or more, each is presented in a consistent format that is described in detail in the next section. Here we provide a brief overview of our treatment of the data and point out the limitations of our analyses.

Full accounts are included for species for which there was at least one encounter over 100 km from the banding site; banding statistics for other species banded or encountered in Canada are included in Banding Summary. Each species account provides one or more maps showing movement patterns, followed by a narrative and a listing of selected encounters reported in detail. Each account concludes with a summary table of standard information and a map showing the distribution of bandings for that species in Canada.

The survival or movements of species for which there are 100 or more encounters have often been analyzed in published works. In such cases, we provide a précis of the results in our narrative (including some important references from later than 1995, including Banding Office data on maximum longevity to 2007). When there is little or no literature, we have tried to highlight the most important patterns indicated by the encounters.

The list of selected encounter records in each account includes examples of typical movements, but also includes cases that will interest banders — for example, records showing unusually long-lived or fartravelled birds, movement outside the normal range of distribution, and cases of apparent "reverse" migration. We recognize from our own experience as banders that it is often the unusual or spectacular encounter that stimulates a bander's interest, and we hope that some of those listed will serve this purpose.

The database used in preparing this atlas series includes all records of birds banded under the North American scheme that were 1) banded in Canada and encountered anywhere or 2) banded elsewhere (usually in the United States but a few in Central America or on Pacific islands) and encountered in Canada. Encounters in Canada of birds banded under other banding schemes (chiefly in northwestern Europe and Greenland) are also included to the extent that we could find out about them, because these records add so much to our knowledge of the distribution and movements of Canadian birds (Tuck 1971; Dennis 1981). Encounters of this sort from the period prior to 1975 were extracted from European banding reports and other published sources. Those from 1975 to 1995 were obtained in part from literature but primarily from the European Union for Bird Ringing, or EURING, and we recognize that this atlas gives an incomplete picture of European-banded birds encountered in Canada. At some modest risk of creating a diplomatic incident, we have also included in this series a few records that did not involve Canadian territory — from the French islands of St. Pierre and Miquelon (located off the south coast of the island of Newfoundland).

The most obvious limitation of this atlas series is that it deals only with bandings or encounters occurring within Canadian boundaries and the seas immediately offshore. U.S. records that did not involve Canadian territory had to be excluded because the sheer volume of data for North America as a whole was simply beyond our means to handle. (The project was well under way before the dawn of the computer age.) Nevertheless, we felt that the Canadian database was sufficiently large and geographically representative to justify restricting our coverage. We hope that this atlas series will stimulate our American colleagues to collaborate in a more comprehensive continental assessment of banding and encounter data.

Banding data can be misleading if not interpreted carefully with a full understanding of biases and limitations. There is always uncertainty about specific records. The person reporting an encounter has to provide accurate information on the band number (which is usually the means of identifying the species); however, band numbers are easily misread, and only rarely is the actual band returned with the report of finding. In addition, the finder must accurately report date, place, and other details, and investigation shows that reports may often be incomplete or incorrect (Houston and Francis 1993). Data entry is another common source of mistakes. Given the qualifications necessary to get a banding permit, bander error is a less likely source of problems. However, occasional odd encounters are most plausibly explained as mistaken species identification on the part of the bander. This can occur, for example, when chicks are banded in mixed colonies of gull or tern species.

Although we could not check every record, we have checked the details of the most striking encounters. In most cases, there are no data entry errors and no clue as to whether the band number was read correctly. We therefore had to use our judgement as to whether to include certain odd records. When a record was clearly in error we excluded it, but when it was merely suspicious we retained it, usually calling attention to it in the species account. Readers should regard all individual records with a degree of caution, however, and give greatest credence to overall patterns of movement. Although it was sometimes discouraging (although hardly surprising) to see that errors had crept into this large database, we are convinced that the value of the data set as a whole justifies our summarizing all the available data for public scrutiny.

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