Ardea
Official journal of the Netherlands Ornithologists' Union

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Fransson T. (2001) To analyse ringing recoveries in a national atlas: Examples from the Swedish project. ARDEA 89 (1): 21-30
Preparations to produce recovery atlases showing results from extensive bird ringing activities are firmly under way in many ringing schemes. In Sweden such a project was initiated long ago and the first volume out of three will now soon be published. To standardise the presentation of results for different species has been a difficult problem to solve. The number of recoveries varies substantially between species as well as where and how they have been ringed and recovered. When selecting recoveries for subsequent analysis, it is therefore not only important to take the species' biology into account but also to consider the characteristics of ringing and recovery data. It is also important to have in mind that spatial variation in reporting rates and hunting pressures affects the geographical distribution of recoveries. Relatively few recoveries can sometimes give a good hint of a species migratory pattern. Even when many recoveries are available, sample size may become very small when the sample has to be broken down into different age categories or seasons. Another problem can be that recoveries have accumulated during almost a century. Behavioural changes may have occurred meanwhile, such as in the Canada Goose Branta canadensis introduced in Sweden, which seems to migrate further and further south in winter in recent years. An atlas is not just a way of presenting ringing results but many also be used in future planning of bird ringing activities


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