Summer-autumn feeding ecology of Pied Flycatchers Ficedula hypolueca and Spotted Flycatchers Muscicapa striata: the importance of frugivory in a stopover area in north-west Iberia

Abstract

North-west Iberia is a crucial stopover region for European populations of Pied Flycatchers Ficedula hypoleuca and Spotted Flycatchers Muscicapa striata during their summer-autumn migration. Both species are almost completely insectivorous during breeding in Europe and wintering in sub-Saharan Africa, but are known to consume fleshy fruits during summer-autumn migration, though no detailed investigations have been carried out over long periods of time. In this study, the summer-autumn feeding ecology of Pied and Spotted Flycatchers in a stopover area in north-west Spain, with a landscape of hedgerows and irrigated meadows, was studied for five consecutive years (2002–2006). In general, the passage of both flycatcher species was noticeable from mid-August to the end of September, with a peak in the first ten days of September. The two flycatcher species consumed fruits throughout the stopover period in all years, with constant intensity of frugivory in time, though the importance of fruits was almost three times greater in the diet of Pied Flycatchers ( c . 30% of feeding acts) than in that of Spotted Flycatchers ( c . 10% of feeding acts). Both species preferred Dogwood Cornus sanguinea fruits, but also ate Elder Sambucus nigra berries and Bramble Rubus spp. drupelets. The high level of selection of Dogwood fruits was probably linked to their high lipid content, an essential nutrient for fattening in long-distance migrant passerines. Hedgerows and wood edges in north-west Iberia are rich in fleshy fruits but threatened by intensive farming. Their conservation and restoration are proposed because they seem to be high-quality stopover habitats for partially frugivorous passerines during summer-autumn migration.