Abstract
BackgroundFor most Afro-Palearctic migrants, particularly small songbirds, spatiotemporal migration schedules and migratory connectivity remain poorly understood. We mapped migration from breeding through winter of one of the smallest Afro-Palearctic migrants, the willow warbler Phylloscopus trochilus, using geolocators (n = 15).ResultsBirds migrated from North European breeding grounds to West Africa via the Iberian Peninsula following a narrow corridor along the West Coast of Africa. Birds then dispersed across the northern Savannah with termination of migration highly variable among individuals. The termination of migration appeared not to be related to timing, current and previous years’ vegetation conditions or biometrics. During winter, most birds moved southwards to improved vegetation.ConclusionThe willow warblers showed a large, unexpected longitudinal spread in winter sites of more than 3000 km between individuals breeding within a 500 m range resulting in a low degree of connectivity. The large wintering area may well be related to generalist behaviour in the species. Our findings contribute to understanding the link between breeding and wintering ecology in long-distance migratory birds.
Highlights
For most Afro-Palearctic migrants, small songbirds, spatiotemporal migration schedules and migratory connectivity remain poorly understood
Connectivity is defined as a relative measure: It is high if little mixing occurs, i.e. individuals from different breeding sites stay separated in winter, and it can be low even if wintering occurs within a limited area as long as the whole population winters within the same area
We focus on the resulting migratory connectivity and the behaviours causing it at the individual level
Summary
For most Afro-Palearctic migrants, small songbirds, spatiotemporal migration schedules and migratory connectivity remain poorly understood. Migration is an adaptation to seasonal environments [1, 2] and billions of small songbirds travel vast distances from Palearctic breeding to sub-Saharan wintering grounds every year [3]. Understanding the drivers of these travels and the links to the seasonally changing environments requires detailed knowledge of the spatiotemporal migration pattern. How much individuals from the same breeding site mix during the non-breeding season with birds from other sites within the same population [7], is essential for understanding ecology and population dynamics [8,9,10,11]. Connectivity is Lerche-Jørgensen et al Movement Ecology (2017) 5:17 commonly low in long-distance migratory birds [12] but some notable exceptions have been reported [9, 11]
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