干旱区生态环境知识资源中心

Timing the annual cycle according to local conditions is crucial for animals in seasonal environments, because individual resource requirements must match seasonal resource availabilities. Pre-nuptial spring migration is especially time constrained in many migratory species, and thus tight adjustments of departure and arrival times to local environmental conditions can be expected. We determined non-breeding residences of Common Redstarts, an insectivorous Palearctic-African migrant, from a central European population. Non-breeding residencies of three out of four males were located in the northern Sahel of West-Africa; a single individual did not cross the Sahara desert, but spent the non-breeding season in Northern Africa instead. Additionally, we related local vegetation phenology and the timing of spring migration in a central and a northern European population differing largely in breeding site latitude. The arrival at and departure from the African sites was similar in birds from the central and the northern population. Departure from the non-breeding sites was not related to seasonal deterioration of vegetation. Birds from both populations arrived at their distant breeding grounds in the same time period. Since spring green-up times differed greatly, birds from the two populations encounter different phenological conditions at arrival. The missing relation between vegetation phenology and migration timing may indicate that spring migration in redstarts is triggered by other factors than vegetation development at least at the non-breeding sites. A general cue such as local photoperiod might be the candidate factor, which would also explain the small variation between the populations.