Seabird population review shows long-term declines

A retrospective study published in the fall of 2015, looked at seabird populations from 1950 to 2010, and found the overall long-term trend for most species was downward. The University of British Columbia–based authors suggest that multiple factors play a role.

Birds breeding on oceanic islands and those that which wide-ranging oceanic habitat needs are at greatest risk. For example, the data indicates that, unless the trend is reversed, by 21000 between 28 and 65% of birds breeding on oceanic islands will be extinct. The wide-ranging species—e.g. albatrosses, terns and skuas—showed the highest levels of decline.

These results are not surprising. The situation on oceanic islands has been well studied. Introduction of exotic species such as cats and rats has resulted in high levels of predation, particularly on eggs and hatchlings. Highly pelagic species can be impacted by problems in any part of their normal range.The authors cite entanglement in fishing gear, overfishing of key food species, direct exploitation (harvesting of eggs, chicks and adults by humans), and pollution, among other potential hazards facing these birds. Climate change and the resulting severe weather plays a role, as seen in the 2014 seabird wreck off the European coast.

Another factor, less often discussed in the general media, is the result of exploitation of other marine wildlife, including whales, dolphins and sea otters which creates changes in the quality, quantity and distribution of prey species. Seabirds of small body size, those with specialised diets, and energy-intensive or surface foraging species are particularly impacted by overfishing.

While oil spills are not the primary cause for serious seabird population declines, preventing spills, preventing seabirds from being impacted when spills do occur, and providing best possible care to those that are affected by oil can have a positive impact on these declining populations by returning these birds to the reproductive pool.

On a positive note, the Sixth Meeting of the Parties (2015) of the Agreement on Conservation of African-Eurasian Migratory Waterbirds (AEWA), administered by the United Nations Environment Programme, agreed on action plans for highly threatened seabirds which include the establishment of marine protected areas, modification of fishing gear to reduce seabird by-catch and actions to reduce marine debris.

Resources:
Plaeczny, M., et al. 2015. Population Trend of the World’s Monitored Seabirds, 1950-2010. PLoS ONE 10(16):e0129342 (doi:1371/journal.pone.0129342.
Africa: Countries Commit to Tackling Multiple Treats to Migratory Waterbirds. Allafrica.com. accessed online 12.20.2015