MIGRATORY DISPOSITION OF SMALL PASSERINES IN CENTRAL-EUROPE - MOLT, BODY-MASS, FAT DEPOSITION, AND STOPOVER LENGTH

Authors
Citation
A. Kaiser, MIGRATORY DISPOSITION OF SMALL PASSERINES IN CENTRAL-EUROPE - MOLT, BODY-MASS, FAT DEPOSITION, AND STOPOVER LENGTH, Journal fur Ornithologie, 137(2), 1996, pp. 141-180
Citations number
81
Language
TEDESCO
art.tipo
Article
Categorie Soggetti
Ornithology
Journal title
ISSN journal
0021-8375
Volume
137
Issue
2
Year of publication
1996
Pages
141 - 180
Database
ISI
SICI code
0021-8375(1996)137:2<141:MDOSPI>2.0.ZU;2-S
Abstract
Data from approximately 200,000 birds caught during their stopover on southward migration at lake Constance (SW Germany) were analysed for t he extent of migratory disposition. Variation in migration patterns (t he increase in number of arriving birds) correlates well with the onse t of migratory disposition in a sub-sample of approximately 13,000 fir st-captures of 58 species, mainly warblers (Acrocephalus, Sylvia, and Phylloscopus), tits, and thrushes. 72% of all birds partially or fully renewed their body feathers during the study period, indicating that most birds were in the early stage of their migration. Body condition changed significantly with migratory disposition, thus fat deposition increased with decreasing moult intensity, whereas body mass of first captures increased very slowly over time in some species. Differences in ecophysiological parameters were tested among long-, intermediate- and short-distance migrants as well as between the pre-migration and t he migration period. Long-distance migrants moulted fast, had a minimu m stopover period of only 4.8 days and were considerably fatter than s hort-distance migrants. During migration 90% of all individuals were c aptured only once. These ''fast passage migrants'' or transients can b e distinguished from ''longer resting birds'' using captures if severa l factors including moult progress, moult intensity, fat deposition, s eason, capture time and habitat are considered. A discriminant analysi s revealed that age and wing length also had a significant influence o n the resting strategy in some populations. Combining results from mul ti-factor analyses and theoretical flight distance estimates variation in resting strategy supports a hypothesis of small stages and long st opover periods in most individuals and species.