Double-crested Cormorants (Phalacrocorax auritus) of Leech Lake, Minnesota: Temporal Variation of Diets and Assessment of Differential Prey Selection in Adults

Abstract In 1998, after 160 y without documented nesting, Double-crested Cormorants (Phalacrocorax auritus) recolonized Leech Lake, Minnesota. Competition for nesting space with the state threatened Common Tern (Sterna hirundo), and concern regarding potential walleye (Sander vitreus) and yellow perch (Perca flavescens) population declines prompted culling of cormorants and research into their diet. Stomach contents of adult and subadult cormorants were collected in 2004, 2005, and 2006 (186, 356 and 348, respectively) and from cormorant chick regurgitants in 2005 and 2006 (151 and 114, respectively). Perca flavescens (>70% composition and biomass) and shiner species (Notropis sp.) (>4% composition and biomass) were the main components of subadult and adult cormorant diets in 2004 and 2005 and the diet of chicks in 2005. However in 2006, whitefish species (Coregonus sp.) was the majority of percent biomass consumed by subadults and adults (43.4%) and a large proportion of percent biomass consumed by chick...