POLLEN AS A MARKER IN MIGRATORY WARBLERS, SYLVIIDAE

Pollen were analysed in pollen hems accumulated at the base of the bil l when birds forage in flowers. Among five warbler species, Sylviidae, caught in spring in Denmark, 1.8% (n = 766) of all individuals carrie d pollen horns from spring flowering plants, although the proportion o f hems varied between species (ranged from 0.4 to 4.4%). In contrast, only one individual captured in autumn had pollen hems (n = 655) which contained pollen from spring flowering plants. The analysed hems cont ained predominantly pollen of plant genera Eucalyptus and Citrus restr icted to the Mediterranean; these plant species occurred almost mutual ly exclusively amongst the collected pollen horns. The results indicat e that the Mediterranean is an important stopover area for some warble rs during spring migration, and demonstrate within and between species differences in feeding plant species.