The decline of the Ring Ouzel Turdus torquatus in Britain: evidence from bird observatory data
Ouzel Turdus torquatus bird days has declined significantly in spring at western observatories through which British-breeding birds pass, but not at east coast observatories through which Fennoscandian breeders pass. The extent of decline corresponds roughly to the decline in numbers of British bree...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
1993
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.485.2560 http://blx1.bto.org/pdf/ringmigration/22_4/burfield.pdf |
| Summary: | Ouzel Turdus torquatus bird days has declined significantly in spring at western observatories through which British-breeding birds pass, but not at east coast observatories through which Fennoscandian breeders pass. The extent of decline corresponds roughly to the decline in numbers of British breeders as assessed on the breeding grounds. While these results could indicate that the decline in British Ring Ouzels is caused by problems on the breeding grounds, we also highlight the possibility that differences in the timing and routing of British and Fennoscandian birds when migrating across continental Europe could expose the former to greater risks from hunting. When a species is in decline, various routes can be followed to diagnose the causes. One approach is to examine regional variation in the extent of decline and ask whether possible drivers of decline act more or less strongly in different parts of the range in a manner that correlates with the extent of decline. This approach has been followed successfully, for example, by Green & Stowe (1993) and by Weimerskirch et al (1997), and underpins |
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