Cover image: A male redstart (Phoenicurus phoenicurus) stopping over on Heligoland Island (54° 11′ N, 07° 52′ E) during its northward spring migration. This small insectivorous songbird breeds in the Western Palearctic and migrates to sub-Saharan Africa outside the reproductive period. Redstarts travel alone in a series of nocturnal flights, guided by internal circadian clocks, photoperiodic cues, and magnetic compass information. Like in most migratory songbirds, males precede females on their journey to the breeding grounds—a phenomenon termed protandry. It was no one less than Charles Darwin who provided the first explanation of why sex-specific migratory behavior might have evolved. Patterns of protandrous migration were well known to bird catchers and hunters on Heligoland, even before the establishment of the renowned banding station in 1910. A detailed record of birds caught and banded at Heligoland Bird Observatory (Vogelwarte Helgoland) has been kept ever since, which places it among the longest-lasting time-series of phenological data on bird migration. Today, research is focused on the physiological mechanisms controlling differential timing of migration in males and females. Results presented by Coppack and Pulido in this issue of Integrative and Comparative Biology suggest that the sexes may differ in their endogenous circannual organization and photoperiodicity.
Photo: M. Kraschl. Submitted by Timothy Coppack, "Proximate control and adaptive potential protandrous migration in birds."
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