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Autumn 2006 - Act•ionLine

by Donald S. Heintzelman | Autumn 2006

The Cormorant Wars

Why Are Government Agencies Killing Double-Crested Cormorants?

An increasingly nasty killing campaign, not unlike a war, is currently being waged in North America against a somewhat prehistoric-looking bird named the Double-crested Cormorant (Phalacrocorax auritus).

This cormorant is a fairly large bird, about 33 inches long, with black plumage, webbed feet, an orange-yellow throat pouch, and two short crest-like areas on the feathered head when in breeding plumage.1The cormorant’s food consists largely of fish — occasionally including some species sought by anglers.

The Double-crested Cormorant is the most widely distributed of several cormorant species breeding in North America. The species is expanding breeding activities into some new locations — sometimes at places where other birds such as Great Blue Herons (Ardea herodius), Great Egrets (Ardea alba) and Black-crowned Night Herons (Nycticorax nycticorax) already are breeding, thereby perhaps providing some degree of competition for potential nest sites and food.

Much research remains to be done, however, to accurately understand the behavioral and ecological interactions of nesting Double-crested Cormorants with other nesting birds — especially in Pennsylvania and Ontario.

In Pennsylvania, during the past half-century, Black-crowned Night Herons have nested on several islands in the Susquehanna River. For example, one nesting colony thrived on Rookery Island near Washington Boro, Lancaster County, until sometime in the 1980s when the birds stopped nesting there and, for unknown reasons, abandoned the island.

Common Egrets and Black-crowned Night Herons also nest on Wade Island in the Susquehanna River at Harrisburg, Pennsylvania, and in 2005, there were also 59 cormorant nests on Wade Island. A slow decline of nesting night herons began on Wade Island extending back some five years before the first Double-crested Cormorants arrived on the island. Hence, currently unknown behavioral and ecological factors seem to be responsible for declining populations of nesting Black-crowned Night Herons on at least two islands in the Susquehanna River in Pennsylvania.

In an attempt to stop declining numbers of state endangered nesting Common Egrets and Black-crowned Night Herons on Wade Island, and without any scientific evidence explaining the reasons for the declines of these birds, the Pennsylvania Game Commission decided to shoot up to 50 Double-crested Cormorants nesting on the island.2 The Game Commission asserts that cormorants compete for the island’s trees and shrubs used as nest supports by egrets and night herons, thereby forcing these birds off the island while also causing the death of some trees and shrubs due to accumulations of cormorant guano on the island’s vegetation.

Several ornithologists, however, protested the cormorant shooting on Wade Island: Along with Stacy Small, former Director of Bird Conservation for Audubon Pennsylvania, and nature writer Scott Weidensaul, a Board Member of Audubon Pennsylvania, I find no scientifically valid reason for killing cormorants nesting on Wade Island.

While a scientific study would be needed to determine the factors responsible for declining nesting Common Egret and Black-crowned Night Heron populations on Wade Island and perhaps elsewhere along the Susquehanna River, the Game Commission’s speculation that cormorants caused recent declines in night herons nesting on Wade Island is contradicted by ornithological studies in the Great Lakes region, where Double-crested Cormorants do not negatively impact regional nesting populations of Common Egrets or Black-crowned Night Herons.

In Ontario, at Presqu’ile Provincial Park, a similar dispute exists regarding shooting in 2006 of nearly 3,000 adult Double-crested Cormorants (collectively some 6,000 during the past several years) on the park’s High Bluff Island in Lake Ontario. It appears the primary stated reason for this cormorant war is to protect other colonial nesting waterbirds, and to satisfy complaints of anglers.3 What are the results of this cormorant management effort by Ontario Parks and the Ontario Ministry of Natural Resources? Thus far, it has cost at least $250,000 per year, and the death of thousands of cormorants. In addition, dangerous levels of mercury pollution emanate from the bodies of decomposing cormorants put into a compost pile, due to mercury pollution of the fish they eat. In fact, in 2005, the contaminant problem forced the transport of mercury-polluted compost to an area landfill, and in 2006 it led to an enlargement of the park’s compost pile in an effort to “dilute” the mercury contamination.4 The disruptive activities associated with cormorant shooting also caused the nesting failure of Red-tailed Hawks (Buteo jamaicensis) in the park.

Various Canadian animal protectionists also documented extreme cruelty during the cormorant shooting activities, with wounded birds suffering for many hours before death, helpless nestling baking in the sun without their parents coming to shade them, and many hundreds of cormorants landing alive and wounded in trees or nearby water without being retrieved where they would suffer painful and lingering deaths.5 One hopes Ontario Parks and the Ontario Ministry of Natural Resources will become responsible agencies and stop their unjustified war on cormorants.

Friends of Animals members can oppose cormorant killing by writing to the following Pennsylvania and Ontario officials:

Carl G. Roe, Executive Director, Pennsylvania Game Commission
2001 Elmerton Ave.
Harrisburg, PA 17110-9797
United States

Susan Grigg, Ontario Ministry of Natural Resources

  • 1. Roger Tory Peterson and Virginia Marie Peterson, A Field Guide to the Birds of Eastern and Central North America (5th ed.; 2002).
  • 2. The Pennsylvania Game Commission’s chief law enforcement officer, John A. Shutter, Jr., claims his agency has the legal authority to kill nesting Double-crested Cormorants: “The reduction of the population of Double-Crested Cormorants on Wade Island will be done under the authority of a Federal migratory bird depredation permit. … We believe this action is necessary to protect a rookery of Black-Crown night barons [sic], which are classified as an endangered species in Pennsylvania. While we did not place notice in the Pennsylvania Bulletin, we did make known our intent through a news release to media outlets.” John A. Shutter, Jr., unpublished letter of May 1, 2006; see also Pennsylvania Game Commission News Release #49-06, “Game Commission Announces Effort to Protect Nesting Colony of Great Egrets and Black-crowned Night Herons on Wade Island” (20 Apr. 2006); and Marc Levy, “Pennsylvania Puts Cormorants on Hit List” - Associated Press (16 May 2006).
  • 3. See MacKay, Barry Kent et al., “Memo to John Ramsay, Ontario Minister of Natural Resources and John Immerseel, Zone Manager, Ontario Parks, Regarding Double-crested Cormorant Killing at Presqu’ile Provincial Park, Ontario” (12 Apr. 2004); Doug McRae, “Sorry and Costly Affair” - The Independent [of Brighton and East Northumberland County, Ontario] (7 Jun. 2006).
  • 4. See “Sorry and Costly Affair” (note 3 above).
  • 5. See Memo to John Ramsay and John Immerseel and “Sorry and Costly Affair” (note 3 above).
Donald S. Heintzelman

Act•ionLine Autumn 2006

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