Simple facts about Double-crested Cormorants

Double-crested Cormorants are being systematically eliminated from the Great Lakes basin by a joint concerted effort by state and provincial fish and wildlife government agencies primarily to appease an irate sport fishing lobby that have long accused the bird of eating ‘too many fish’.

In some cases, such as Point Pelee National Park, government agencies argue that double-crested cormorants are ‘destroying’ trees and ground vegetation and must be killed to ‘preserve biodiversity’. This argument is being made across the southern Great Lakes where cormorants typically nest in trees.

Parks Canada is part of a broader partnership that includes the Ontario Ministry of Natural Resources, and the U.S. Fish and Wildlife Service whose mandate is to actively kill cormorants throughout the bird's nesting habitat and migration route - leaving no place safe for these birds anywhere.

Like wolves, the double-crested cormorant is being scapegoated for political reasons – to appease an aggressive sport hunting and fishing lobby. But here are some “straight-shooting” facts about double-crested cormorants:

Double-crested cormorants are a North American migratory bird native to Ontario.
They nest on the Great Lakes in the spring and summer, and winter in the southern United States.
They are black birds found in large nesting colonies ranging from several hundred to several thousand birds. Their colonies are typical of other colonial waterbirds found throughout the world.
The large dense colonies during nesting periods serve as a natural barrier against predators that feast on cormorant eggs and chicks. These predators include other colonial waterbirds such as gulls and herons. Populations are self-regulating once colonies become too dense.
The largest colony in North America is found on the Columbia River estuary in Washington State at 15,000 nesting pairs. The largest recorded colony was in Baja, Mexico at 300,000 birds in 1913.
While their colonies may be dense, colonies are not numerous across the Great Lakes.
They prefer to nest on isolated islands, both on the ground and in trees.
Tree nesting cormorants will eventually kill the host tree through the deposit of their guano.
The process of killing trees prematurely is a naturally occurring process found throughout the natural world. Beavers kill trees by damming creeks and flooding forest areas. Natural wildfires also kill trees. These trees eventually become “snags” providing habitat for an array of wildlife such as woodpeckers and den dwelling animals. Snags eventually breakdown into soil.
Thirty years ago, these birds were on the verge of extinction on the Great Lakes. Toxic pollution almost wiped them out. As a result, toxic chemicals such as DDT and PCBs were banned.
Double-crested cormorants are currently reoccupying their ecological role within the Great Lakes system.
Cormorants feed exclusively on live fish and are considered to be a skilful predator.