Integrative and Comparative Biology Advance Access published online on June 8, 2009
Integrative and Comparative Biology, doi:10.1093/icb/icp029
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Proximate control and adaptive potential of protandrous migration in birds
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*Institute of Avian Research, Vogelwarte Helgoland, 26386 Wilhelmshaven, Germany; Max Planck Institute for Ornithology, Vogelwarte Radolfzell, 78315 Radolfzell, Germany; University of Zurich, Zoological Museum, Winterthurerstrasse 190, 8057 Zurich, Switzerland; Department of Zoology and Physical Anthropology, Faculty of Biology, Universidad Complutense de Madrid, 28040 Madrid, Spain
Correspondence: 1E-mail: coppack{at}access.uzh.ch
Migration determines where, when, and in which order males and females converge for reproduction. Protandry, the earlier arrival of males relative to females at the site of reproduction, is a widespread phenomenon found in many migratory organisms. Detailed knowledge of the determinants of protandry is becoming increasingly important for predicting how migratory species and populations will respond to rapid phenological shifts caused by climatic change. Here, we review and discuss the potential mechanisms underlying protandrous migration in birds, focusing on evidence from passerine species. Latitudinal segregation during the non-breeding period and differences in the initiation of spring migration are probably the key determinants of protandrous arrival at the breeding sites, while sexual differences in speed of migration appear to play a minor role. Experimental evidence suggests that differences between the sexes in the onset of spring migratory activity are caused by differences in circannual rhythmicity or by photoperiodic responsiveness. Both of these mechanisms are hardwired and could prevent individuals from responding plastically to chronic changes in temperature at the breeding grounds. As a consequence, adaptive changes in both the timing of arrival in spring and of reproduction will require evolutionary (genetic) changes of the cue-response systems underlying the initiation and extent of migration in both males and females.
"In many cases special circumstances tend to make the struggle between the males particularly severe. Thus the males of our migratory birds generally arrive at their places of breeding before the females, so that many males are ready to contend for each female. I am informed by Mr. Jenner Weir, that the bird-catchers assert that this is invariably the case with the nightingale and blackcap, and with respect to the latter he can himself confirm the statement." Charles Darwin (1874)
"The young birds of the summer open the grand autumnal flight, unaccompanied by any old, the very finest old males at the close of the season bringing up the rear. In spring, however, quite the reverse invariably takes place, then the most perfect old males appear first, followed soon by old females, and later by younger birds of less perfect appearance." Heinrich Gätke (1879)