Nocturnal behavior of the Common Loon, Gavia immer

Abstract

Very little is known about nocturnal activity of Common Loons (Gavia immer). Knowledge of both diurnal and nocturnal behavior is needed to gain a complete understanding of their ecology. I used night vision light intensifiers to observe noctur-nal behaviors of Common Loons. Results were consistent with the hypothesis that, as visual predators, loons would not for-age at night and also that they would spend the majority of their time resting (92%). Loons, however, were just as active locomoting (patrolling) during the night as they were during the day. This suggests daily energy budgets need to be reexam-ined to incorporate this overlooked aspect of loon behavior. Lastly, loons on large lakes with multiple loon territories spent more time locomoting than loons on lakes that had just a single pair.