Cormorants diet causes lake officials to worry

From the Galion Inquirer -

A pilot study to determine the diet of double-crested cormorants on western Lake Erie is being conducted by several local agencies. Many sport anglers are concerned about the rapid increase in nesting cormorants and the possible adverse affect on local fish populations. The study may give some indication of possible negative impacts on Lake Erie's ecosystem.

The colony on West Sister Island has grown from 180 breeding pairs in 1992 to close to 1,500 in 1996. "We need to understand how the growing population of these birds may be impacting other wildlife both in and around the lake," said Mark Shieldcastle, biologist with the Division of Wildlife. Besides the concern for the fishery, another growing concern is the potential for habitat destruction and nesting competition with wading birds. West Sister Island is a crucial nesting site for black-crowned night herons, great egrets and great blue herons and supports the largest colonies of these wading birds in the Great Lakes.

The ammonia-rich droppings from large colonies of cormorants can destroy island vegetation, including many immature trees, shrubs and ground cover where the wading birds nest. Cormorants may be responsible for declining numbers of herons and egrets which depend on the islands for nesting.

Double-crested cormorants are slender, black birds often seen flying low in single file formation across the water or standing erect on rocks or dock poles. Adults measure 29 to 36 inches in length with an average wingspan of 54 inches. Both males and females are solid black with a yellow-orange patch on the throat, a double head crest of upcurled feathers on each side of the head and a long tail. These birds are federally protected under the Migratory Bird Treaty Act.

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