Double-crested Cormorants (Phalacrocorax auritus) on the Move in the Beaver Archipelago, Northern Lake Michigan

摘要

Double-crested Cormorant (Phalacrocorax auritus) foraging locations in northern Lake Michigan were recorded in 2003 and 2010. In the interim, the invasive round goby (Neogobius melanostomus) appeared in 2006, and control of Double-crested Cormorants was initiated in 2007. Spatial data from 2003 and 2010 were analyzed to determine whether foraging distributions differed between sample periods. A multi-response permutation procedure found that a significant shift in foraging locations occurred between sample periods. Groups of Double-crested Cormorants foraged in the same key locations in both years, but foraging range expanded overall in 2010. Range expansion could be a response to the presence of the round goby, which is an abundant food source throughout Lake Michigan. The 2010 foraging location data corresponded with the early departure of Double-crested Cormorants from the Beaver Archipelago. The combined effects of control and the appearance of round goby in diets resulted in changes in numbers and distributions of foraging Double-crested Cormorants.