Wednesday, August 14, 2013

Cormorant Conundrum

Double-crested Cormorant (c) John Ashley
A Double-crested Cormorant cruises the sunset waters of Ninepipe reservoir

The Double-crested Cormorant (Phalacrocorax auritus) is a Montana native with an image problem. The species survived a DDT-caused population crash during the 1960's only to have their current recovery greeted with considerable disdain in some quarters.

Of the six North American Cormorant species, the Double-crested is the only one that makes it very far inland from coastal waters. They are summer visitors to Montana, and the Cormorants that summer on the east side of the Rockies generally spend the winter along the Gulf Coast, from Texas to Florida.

Cormorants went missing from Montana during the 70's and early 80's. A slow recovery that started in the 90's suddenly boomed during the last 5-10 years in our state. Across the continent, Cormorant numbers have similarly blossomed during the last 30 years.

Instead of viewing this recovery of a native species as a huge success, many people in the fishing industry felt threatened by competition from a fishing bird. Many of these folks weren't around when cormorants were common, 40+ years earlier, so this was seen as a "new" threat. Because of the public outcry, the U.S. Fish and Wildlife Service was compelled to draw up a new Cormorant conservation plan in 2003. Under the current rules, a total of 160,000 Cormorants are allowed to be legally killed each year. On average, "only" about 40,000 are killed each year in 13 states, not counting many thousands of eggs that are intentionally oiled or crushed each summer.

In 2006, biologists conducted a study to find out what Cormorants were really eating at Canyon Ferry Reservoir, near Helena. What they found would surprise most people. The birds ate mostly fish and smaller amounts of amphibians and crustaceans, and the fish eaten were mostly small - less than 6" long - from mostly bottom-dwelling and schooling species. Their diet broke down this way: 44% stonecat (catfish), 13.2% trout, 13.2 suckers, 15.5% dace, 6.6% sculpins, and 7.7% crayfish.

This study showed that the Cormorant diet at Canyon Ferry was composed of 87% non-game fish and 13% game fish (trout). In other words, Cormorant diets just barely overlapped with human fishing interests. But it was too late to change the public's negative perception of these birds.

Cormorants eat fish, and they always have. People enjoy catching fish, for fun and for food. But until we acknowledge which fish species the Cormorants actually eat - and don't eat - the Cormorant will remain a native bird with an undeserved image problem.