Double-crested cormorants are an invasive waterbird on Lake Champlain. Historically, cormorants have inhabited larger bodies of water than Lake Champlain, however, since they became protected in the Migratory Bird Treaty Act in 1972, the cormorant population has exploded on the Lake.
Recognized as harmful to Lake Champlain's world-class fisheries, annual funding is usually earmarked to help control their populations through shooting, egg oiling, and harassment to discourage egg-laying.
Cormorants have a big appetite for Lake Champlain's fish. The 12,000-20,000 cormorants on Lake Champlain consume about 2-4 million pounds of fish annually. Left uncontrolled, cormorants could significantly harm the fish populations on Lake Champlain. Cormorants also displace native waterbirds such as the common tern, while destroying vegetation on nesting islands. Four Brothers Islands, for example, have experienced substantial tree and shrub loss due to cormorant nesting. However, with proper cormorant control, marked habitat improvement has been seen.