Predation and food-weather interactions drive colony collapse in a managed metapopulation of Arctic Terns (Sterna paradisaea)

• Main Authors: Scopel, Lauren C., Diamond, Antony W
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press (a division of Canadian Science Publishing) 2017
• Subjects: Arctic; Meganyctiphanes norvegica; Sterna paradisaea; Seal Island
• Online Access: http://hdl.handle.net/1807/81146; http://www.nrcresearchpress.com/doi/abs/10.1139/cjz-2016-0281

Seabirds are considered bioindicators of bottom-up ecosystem processes, owing to seabirdsâ dependence on marine prey. However, ground-nesting seabirds are susceptible to predation, which can limit their use as bioindicators. Machias Seal Island (MSI) supported the largest colony of Arctic Terns (Sterna paradisaea Pontoppidan, 1763) in the Gulf of Maine metapopulation, but prolonged breeding failure led ~90% of terns to abandon the colony in 2006. We analyzed twelve years of food, weather and predation data using logistic regression models to determine which had the strongest influence on breeding success. Food-weather interactions were important; under low rainfall, more euphausiids (Meganyctiphanes norvegica Sars, 1857) in the diet increased breeding success, but euphausiids had a negative effect as rainfall became moderate or high. Predation by Herring Gulls (Larus argentatus Pontoppidan, 1763) increased following the cessation of lethal predator control; we identified a predation threshold of 25%, beyond which terns could not breed successfully. The collapse of MSIâ s tern colony can be attributed entirely to gull predation. The breeding success of terns at MSI cannot be used as a bottom-up ecosystem bioindicator without accounting for predation. Managers of ground-nesting seabirds should consider predation and food as equally valid potential causes of population or reproductive declines. The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author.