Food and fattening of migrating warblers in some French marshlands.
Migrating passerines adopt various strategies in their departure from Europe. Apart from the routes and timing of passage, there are differences in the extent to which species fatten and take long single flights. A previous paper (Bibby and Green 1981) reported on migration strategies of Reed Acrocephalus scirpaceus and Sedge Warblers A.schoenobaenus drawing results from England and Portugal as well as the present study. We showed that selection of a time and place for fattening depends on the existence of an abundant food supply suitable for the feeding methods of the particular species. Insufficient is known of the foods of most species to explain the routes and timing of their migrations. This paper deals with seven species of warblers at three marshland sites, and investigates the extent to which each species was fattening and how they were feeding to enable this.