Double-crested cormorants common at Lake

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By Sylvia Brockner

One of the most common birds at Evergreen Lake and the most asked about is the double-crested cormorant. For many years, cormorants were largely seacoast birds, found along the rocky cliffs on both the Atlantic and Pacific coasts.

There were only four records of cormorants in Colorado prior to 1912, and these were considered to be “rare winter visitors” in western Colorado.

In 1931, the first breeding record was reported by Bailey and Neidrach, with a total of eight pairs nesting at Barr Lake. By 1939, that colony had 30 pairs, and by 1995 it had 248 pairs.

By 1995, the state population had increased to 1,000 pairs — a large and rapid increase in 64 years. They nest in a group of trees, or if trees are not available will nest on the ground. They are now spread fairly well around the state, except for the Western Slope. They will nest near any body of water that has an adequate supply of fish to feed the colony. They are found today in the reservoirs northeast of Denver, at Barr Lake and other plains reservoirs such as those near Pueblo, west to the San Luis Valley and some in north-central Colorado and almost on the Wyoming border. With colonies or birds seen all around the Western Slope, it is expected that they will be seen there soon.

Cormorants live almost entirely on fish but also consume crayfish, crabs and shrimp. Double-crested cormorants, banded in Colorado in summer months, were found along the Texas and Mexican Gulf Coast in winter. Which means many of the birds nesting here now may find themselves in crude oil this winter.

Cormorants usually have three or four young a year, but may have more. These birds have been used by man for centuries to catch fish for human consumption. The fishing is done by placing a ring around the bird’s neck so that it cannot swallow the fish it catches. The cormorant then swims back to the boat, where the owner removes the fish from its mouth and sends it out again. This is no longer an economical way to fish, so it is not done anymore. But it is still done in the imperial household for its cultural interest and as a tourist attraction.

Cormorants’ eyes are adjusted for both aerial and underwater vision. When fishing, they actually pursue the fish under water, swimming with their wings and their webbed feet, following the fish with their underwater vision.

Our double-crested cormorant has two feather tufts on the top of the head or crest during the breeding season. These feathers are shed after the season is over, and the rest of the year they are not a method of identification. Cormorants are difficult to identify if you are where several species occur. It is accomplished mostly by the color of their bare, unfeathered face. We have only the double-crested cormorant in Colorado as breeding birds, but once in a while one of the young, eager birders from Fort Collins or Boulder finds one of the unusual cormorants. These are birds that have probably been blown in on a storm. They seem to hang around for a few days and then disappear.

The double-crested cormorant do not breed before they are 3 years old. They are pushy birds and take over the best locations in a colony. As the cormorants increase in the colony, the great blue herons decrease.

Most fishermen dislike cormorants because they believe they eat all the sport fish, but actually studies have shown the cormorants usually eat the slowest-moving fish in the pond and are actually helpful to the fisherman by removing the slow-moving fish and frogs and other non-sport fish, leaving the better-grade fish for man.

Cormorants are interesting birds, for in spite of the fact that they fish for their food under water, they have never developed waterproof feathers. Their feathers are not waterproof, and after a few dives they become waterlogged. Then they must leave the water and get up on a perch where they can dry their wings by extending them wide to the sunshine.

The greatest harm they do is to the land beneath their colony. Their guano is so hot it burns all the plant life it falls on. This means most of the plant life dies off, and the island is in a very erodible condition; soon it erodes away or there is not enough cover to shelter other birds or animals.

So far they have not tried to nest at Evergreen Lake, and I sincerely hope they will not. They can become a real problem. They are seen regularly drying their wings on the sandbar at the inlet and on the dam where the fishing is good. They swim very low in the water and are often thought to be loons.