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Birds of Indian Subcontinent

The relationship between geographic variation in clutch size and migration pattern in the Yellow Wagtail

Publication Type:Journal Article
Year of Publication:1996
Authors:Bell, CP
Journal:Bird Study
Volume:43
Date Published:1996
ISBN Number:0006-3657
Keywords:Africa, Asia, Budytes flavus, Eastern Asia, Eastern Europe, Europe, India, Motacilla, Motacilla flava, Motacillidae
Abstract:Clutch size in the Yellow Wagtail increases by about one egg per 19° of latitude throughout Europe, but at a given latitude larger clutches are laid in western than in eastern Europe. In eastern Asia there is evidence of a reverse latitudinal cline, in which clutch size is smaller at higher latitudes, and considerably smaller than in Europe at equivalent latitudes. These trends suggest that smaller clutches are laid by populations with access to extensive wintering areas in east Africa and south-east Asia, whereas larger clutches are laid by populations with more restricted wintering areas in west Africa and India. Higher winter mortality in the latter populations may reduce breeding density, leading to less competition for resources and allowing larger clutches to be produced.Clutch size in the Yellow Wagtail increases by about one egg per 19° of latitude throughout Europe, but at a given latitude larger clutches are laid in western than in eastern Europe. In eastern Asia there is evidence of a reverse latitudinal cline, in which clutch size is smaller at higher latitudes, and considerably smaller than in Europe at equivalent latitudes. These trends suggest that smaller clutches are laid by populations with access to extensive wintering areas in east Africa and south-east Asia, whereas larger clutches are laid by populations with more restricted wintering areas in west Africa and India. Higher winter mortality in the latter populations may reduce breeding density, leading to less competition for resources and allowing larger clutches to be produced.
URL:http://www.tandfonline.com/doi/abs/10.1080/00063659609461026
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