PREPRINT: Update on the conservation status of Townsend's Shearwater (Puffinus auricularis): distribution of breeding colonies, reproductive success and population trends under various conservation scenarios

Description

Abstract (English)

Townsend’s Shearwater (Puffinus auricularis) is a critically endangered seabird. Its distribution is restricted to the Pacific Ocean and ranges from Mexico to Central America. Nearly 20 years ago, the breeding population of Townsend’s Shearwater, which is endemic to the Revillagigedo Archipelago in Mexico, was estimated to consist of fewer than 100 breeding pairs. Since then, conservation initiatives, including eradicating invasive mammals, have been implemented in the archipelago. We assessed the current status of Townsend’s Shearwater by mapping the distribution of breeding colonies, estimating breeding population size, evaluating reproductive success, describing ongoing threats and modelling population trends under different conservation scenarios. From 2016 to 2024, we conducted field surveys on the islands of Socorro and Clarión using acoustic monitoring techniques in historical nesting areas. We estimated that the breeding population of Townsend’s Shearwater on Socorro consists of fewer than 200 pairs and documented the return of a small breeding population to Clarión after a 30-year absence. However, notable reproductive failure persists due to native predators such as land crabs, snakes and ravens. Indeed, the population has exhibited a slow decline driven by interactions between native and invasive species. Without ongoing restoration efforts, including the removal of feral sheep and cats, the population will likely face extinction. To ensure the survival of Townsend’s Shearwater, it is crucial to implement innovative management actions to improve reproductive success.