Welcome to the American Ornithological Society 2018 Annual Conference. We are pleased to have you join us at the lovely Hilton El Conquistador Resort in Tucson, AZ.
Migration is costly and these costs generally increase with migration distance. Thus, migration distance may carry-over through direct or indirect pathways to influence the reproductive success of individuals. Breeding populations of tree swallows (Tachnycineta bicolor) have differing degrees of migratory connectivity. Thus, some breeding populations have a low degree of variation in migration distance (strong connectivity), while others have a high degree of variation in migration distance (weak connectivity). We expect that in populations with strong connectivity there may be little effect of migration distance on reproductive success, while in populations with weak connectivity, reproductive success may through indirect pathways on the timing of breeding site arrival and the timing of breeding initiation be negatively influenced by migration distance. Using migration data generated from 133 light-level geolocators from 12 breeding populations from across North America we assessed how wintering location and migratory distance may carry-over to impose differing direct or indirect pathways on reproductive success in breeding populations with strong and weak connectivity. Path analyses revealed that the direct and indirect pathways on reproductive success differ between weak and strong connectivity populations. In populations with weak connectivity, clutch size was indirectly negatively affected by migration distance, which was mediated through breeding arrival date and timing of breeding. In populations with strong connectivity, there were no such carry-over effects. These results suggest that migration distance may impact reproductive success through indirect pathways.
