Cormorants on the Comeback Trail in the Prairie State
by John Schwegman
In recent years, Illinoisans have been seeing more and more double-crested cormorants in the state. While once an endangered species here, they now seem well on the way to recovery.
These large black waterbirds are about the size of a small goose and can be mistaken for waterfowl at a distance. Flocks of them fly in lines much like ducks and geese, but their habit of sailing from time to time and their dark color and relatively long tail serve to distinguish them from waterfowl.
At close range their long bill with a hook at the end and their orange throat are good identification characters. The fact that all four toes on their feet are connected by a single web is a clincher if you have a bird in hand.
Cormorants are first cousins of the pelicans and are even more closely related to the anhinga or snakebird of the southeastern states.
Of the five cormorants in the United States, all are restricted to coastal marine areas except the double-crested. It winters in coastal areas, but many move inland in spring to nest along fresh water lakes and large rivers.
The double-crested feeds almost exclusively on fish and it is becoming a common sight to see them diving for fish in the waters of our large rivers and lakes. They often take large fish and bring them to the surface to swallow head-first and whole.
Like herons with which they sometimes nest, cormorants are colonial nesters, building nests of sticks in trees. Their colonial nesting habit makes it relatively easy to locate and count the number of nesting cormorants in Illinois.
Nineteenth century accounts of the birds of Illinois listed the double-crested cormorant only as migrant in Illinois, with the birds seen here supposedly having nested in the lake regions of the upper Midwest.
But there also are old nesting records from along the major rivers of Illinois and the species has probably always been present here as a nesting species.
In 1974 only 12 cormorant nests were known in Illinois. These were in two trees along the Mississippi River at Thomson in northwestern Illinois' Carroll County.
Like the bald eagle and many other fish-eating birds, our cormorants apparently had suffered reproductive failure due to DDT insecticide in the environment.
The double-crested cormorant was listed as an endangered species by the Illinois Nature Preserves Commission in 1971. It was subsequently listed as endangered by the Illinois Endangered Species Protection Board with its first official list of Illinois' endangered and threatened species in 1978.
As with many other species that were threatened by pesticides, cormorants are recovering after the banning of these polluting chemicals.
After 1974, they continued to nest along the Upper Mississippi River where the number of nests in Carroll County increased to 25 by 1979. In 1981 there were 49 nests on the Mississippi and the discovery of two nests on the upper Illinois River indicated that the recovering population was spreading to new breeding territory.
The Mississippi River population increased to 103 nests in 1983 and the cormorants spread to establish five colonies totaling 124 nests in 1989. The new population included colonies near lakes in northeastern Illinois and along the middle Illinois River.
The nest numbers reached 466 at five colonies in 1993, prompting the Endangered Species Board to change the cormorant's status in Illinois from endangered to threatened in 1994.
During the summer of 1995, six colonies were found. Two of these are on the upper Mississippi, two on lakes in northeastern Illinois, one along the middle Illinois River and one at Rend Lake in southern Illinois. The nest total was 676 and DNR bird specialist Vern Kleen says that he thinks more colonies and nests are out there, but were not found.
With double-crested cormorants nesting nearly statewide in increasing numbers, it seems only a matter of time before it is removed from the threatened species list—a living tribute to the value of taking action to clean up our environment.
A benefit of their return is the ease with which these interesting birds can now be viewed. One can hardly drive by Rend Lake on Interstate 57 without seeing several flying or feeding in the lake. The same is true along waterways near other nesting locations.
Keep an eye out for them.
John Schwegman manages the botany program for the Illinois Department of Natural Resources.
Illinois Parks & Recreation • January/February 1996 • 51
Sam S. Manivong, Illinois Periodicals Online Coordinator