Cormorant Conflict

Are double-crested cormorants a welcome sign of water quality, or are they a major threat to vegetation, other birds, and sport fish populations? The Lake Ontario population of these large, black water-birds, often sighted in a haughty, spread-eagle resting posture, is on the rise, and while some naturalists are celebrating, sports fishers are crying foul.

The cormorant's recovery from the effects of DDT and other toxic lake contaminants has been remarkable, with nesting numbers rising from just dozens in the early 1990's to 20,000 around the Lake in 1999. The bird's comeback is an indication of improving Great Lakes health, but cormorants are obtrusive colonizers, and can quickly destroy the vegetation and ground cover at their nesting sites. Their excretions are capable of killing trees, and evidence is growing that their swelling numbers are displacing great blue herons, common terns and black-crowned night herons. At Presqu'ile Point, near Brighton, a massive cormorant colony of 8,000 nesting pairs is threatening the habitat of High Bluff Island.

Cormorants also consume a lot of fish, about half a kilogram a day per bird. In the eastern stretches of Lake Ontario and the upper end of the St. Lawrence River, near the Thousand Islands, cormorants are being blamed for a decline in the smallmouth bass population. Some biologists argue, however, that small fish such as alewife and smelt make up most of the cormorant's diet, with only a minor component coming from "pan-fry" fish.

Advocates of cormorant control have proposed a variety of means, including shooting, oiling of eggs, disturbing nesting birds, and destroying nests. The environmental and ethical issues related to each control method have become part of the ongoing cormorant controversy.