Fruits and seeds are critical food sources for many European passerines during the autumn migration, which in turn contributeto disperse seeds either internally, i.e. after ingestion (endozoochory), or externally, when seeds adhere to the bodysurface (epizoochory). Despite the recognized importance of birds as seed dispersers, the vast majority of studies focusedon endozoochory while the external transport of seeds is frequently invoked as being potentially important, but remainslargely unexplored. Th is is particularly important during the post-breeding migration of passerines, the most ubiquitousand diverse movement of potential seed carriers across Europe and into Africa, which coincides with the fruiting peak ofmany plant species (August – October). Our aim was to evaluate the role of migrating birds as potential long-distance seeddispersers, and comparing the prevalence of epizoochory and endozoochory during post-breeding migration. We sampled926 wild birds in nine locations in Portugal, and retrieved 1833 seeds of 19 plant species dispersed internally and only threeseeds externally attached to three birds ( Serinus serinus , Locustella naevia and Turdus merula ), showing an endozoochoryprevalence 85 times higher than that of epizoochory. Migrating and non-migrating passerines dispersed seeds equally.While two of the seeds transported externally had specifi c adaptations to epizoochory, namely spines ( Torilis arvensis ) andhooks ( Galium aparine ), the third is a large seed from a fl eshy-fruited plant, Frangula alnus (i.e. typical endozoochoroussyndrome). Th ese seeds were found on bird species with diff erent diets, but similar behaviour (ground foragers) and insimilar habitats (open agro-ecosystems). Our results highlight the strong role of migrating passerines as potentially longdistanceseed dispersers and show that, at least in the autumn, the prevalence of epizoochory is several orders of magnitudelower than that of endozoochory.
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