Demographic rates reveal the benefits of protected areas in a long-lived migratory bird

By Andrea Soriano-Redondo, Richard Inger, Richard B Sherley, Eileen C Rees, Fitsum Abadi, Graham McElwaine, Kendrew Colhoun, Olafur Einarsson, Sverrir Thorstensen, Julia Newth, Kane Brides, David J Hodgson and Stuart Bearhop

The conservation of the natural world currently relies on the establishment of protected areas. However, site protection alone does not guarantee good biodiversity outcomes. Here, we take advantage of a 30-y dataset on Whooper swans which provides a rare opportunity to quantify the role of nature reserves in the population dynamics of a migratory waterbird. We find that nature reserves play a key role by boosting the survival of this species and will effectively double its population size by 2030.

Image by Martin Birchall / WWT

Recent studies have suggested that protected areas often fail to conserve target species. However, the efficacy of terrestrial protected areas is difficult to measure, especially for highly vagile species like migratory birds that may move between protected and unprotected areas throughout their lives. Here, we use a 30-y dataset of detailed demographic data from a migratory waterbird, the Whooper swan (Cygnus cygnus), to assess the value of nature reserves (NRs). We assess how demographic rates vary at sites with varying levels of protection and how they are influenced by movements between sites. Swans had a lower breeding probability when wintering inside NRs than outside but better survival for all age classes, generating a 30-fold higher annual growth rate within NRs. There was also a net movement of individuals from NRs to non-NRs. By combining these demographic rates and estimates of movement (into and out of NRs) into population projection models, we show that the NRs should help to double the population of swans wintering in the United Kingdom by 2030. These results highlight the major effect that spatial management can have on species conservation, even when the areas protected are relatively small and only used during short periods of the life cycle.

The full article can be found here