Significant decline observed in Arctic Tern Sterna paradisaea population in northwest Greenland

Abstract

Arctic Terns Sterna paradisaea are an understudied species in Greenland. Outside of the largest colonies, little is known about their current population status and no long-term annual monitoring program has been established. Previous surveys outside of key breeding colonies have been limited to a small number of colonies for single-season studies. This limits our understanding of population dynamics as terns have been shown to have a high degree of variation in annual reproduction and readily move between nearby colonies. Here we present results of the first multi-year systematic survey for breeding Arctic Terns in the High Arctic of northwest Greenland. Surveys took place from 2009 to 2017 and identified eight islands where terns currently nest. A total of 426 nests were counted and annual counts ranged from 25 to 92 nests. Complete reproductive failure in at least one year was noted for seven of the eight colonies, and three colonies comprised nearly 90% of the total population. Mean clutch size ranged from 1.4 to 1.7 eggs. When compared with historical data from the late 1960s through late 1990s, the population has declined by over 50%, with the greatest decline occurring over the past two decades. Four previously identified colonies have been extirpated while three colonies have undergone significant reductions in size.