Phenological divergence, population connectivity and ecological segregation between two allochronic seabird populations

Abstract

**Abstract:** Timing of breeding is a trait shaped to optimize resource use while avoiding adverse conditions. It has been suggested that, in some seabird species, allochronic breeding between summer and winter populations may drive genetic isolation to different extents. However, little is known about the connectivity and ecological segregation between populations fuelling this evolutionary process. This study describes the phenology, connectivity, differences in spatial use, habitat selection, daily activity patterns, and isotopic niche of allochronic populations of the Cape Verde storm-petrel Hydrobates jabejabe breeding in Cima Islet Cabo Verde. We ringed breeders and birds in mist-nets for doing analyses on the populations connectivity, deployed GPS and GLS loggers for studying spatial niche in the breeding and non-breeding season respectively, and for studying the daily activity niche through wet-dry data, and took blood/feather samples for studying the isotopic niche. Summer (hot) population bred from February to August, while the winter (cool) population did it from September to January, showing a very low exchange rate of breeders between them and only a few inter-seasonal breeders. Both populations showed a high spatial overlap in their foraging areas during both, the breeding and the non-breeding period, respectively. Both populations fitted their timing of breeding to pulses of oceanic productivity around Cabo Verde while avoiding rainfalls, suggesting inter-seasonal breeders may be disfavoured. Oceanic productivity was higher for the hot population during the breeding and non-breeding areas and spent a higher proportion of time resting on the water during the non-breeding period. Overall, our results showed two populations well-differentiated in their annual phenological events and very low connectivity among them, but with little ecological segregation. Pulses of oceanic productivity may be driving allochrony but does seem not imply an speciation process. **Authors:** Fernando Medrano¹, Teresa Militão¹, Ivandra Gomes², Mariona Sarda-Serra¹, Monica de la Fuente¹, Herculano Dinis², Jacob González-Solis¹ ¹Institut de Recerca de la Biodiversitat (IRBio) i Departament de Biologia Evolutiva, Ecologia i Cièn, ²Associação Projecto Vitó, São Filipe, Ilha do Fogo, Cabo Verde