Life history, population dynamics and impacts of cat predation on an endemic gadfly petrel in Cabo Verde

Insular fauna often suffers significant predation from invasive mammals, yet robust evidence of their impact from rigorous demographic analysis remains scarce. We aimed to understand the life history and population dynamics of the elusive Cape Verde petrel Pterodroma feae , an endemic seabird of the Cabo Verde archipelago, which is severely predated by cats. We analysed capture-mark-recapture data from birds mist-netted in a courtship area in 2007-2021 and monitored their nests between 2012 and 2021 on Fogo Island. Across all islands where this species breeds, we recorded cat predation rates and made additional captures of petrels in courtship areas. Demographic analysis revealed an 8.8% annual population decline of Cape Verde petrels, primarily driven by a 14.7% surplus mortality among breeders from threats in breeding areas, likely tied to the annual cat predation rate of at least 4% observed in monitored nests. Immature males exhibited lower survival rates, likely due to their increased vulnerability while seeking initial nest sites. The limited connectivity detected among and within islands, along with strong nest-site and mate fidelity rates, highlight the urgency of preventing local extinctions, which would be challenging to reverse. This study emphasizes the unsustainability of cat predation rates and the insufficiency of enhancing breeding success to counter the population decline, and it provides compelling evidence of a concerning decline of the Cape Verde petrel, primarily attributable to cat predation. Moreover, it emphasizes the significance of long-term demographic studies to understand the impact of invasive species on endangered populations.