Contribution à la phénologie de migration et à la biométrie du verdier d'Europe, Carduelis chloris (Linné, 1758) et de la linotte mélodieuse, Carduelis cannabina (Linné, 1758)

This study relates the evolution of the fall migration of two avian species, the greenfinch (Carduelis c. chloris) and the linnet (Carduelis cannabina). The analysis of ringing data collected by the Belgian ringing scheme shows that “Nordic” greenfinch and linnets begin to cross Belgium in October, after the birds of Belgium and borderlands have begun to move and increase in number during the migration season until November. Visible migration, adiposity and biometric data were collected at Beaufays (Liège, Belgium) during the fall migration 1984. We could distinguish three periods of passage: a first period of low intensity, a intermediate period of mass-migration and a last period of low intensity, the intensive passage of the linnets taking place before the passage of the greenfinches and the young birds passing before the adults. Adiposity analysis reveals a succession of periods of thinness and fatness. Biometric study shows an increase in the number of birds whose wing length and wing shape indexes increase during the migration period when bill and tarsometatarsus length shorten. The biometric observation corroborates the ringing results, i.e. an increase of birds with marked migratory features along the fall migration. Meanwhile, this has to be confirmed by researches spreading on several years and the several sites, for breeding as well as far migratory populations.