Forest Preserve District of Cook County, Illinois
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Terns
Nature Bulletin No. 688   October 6, 1962
Forest Preserve District of Cook County
Seymour Simon, President
Roberts Mann, Conservation Editor

TERNS
Since prehistoric times, many kinds of water birds have been congregating in vast colonies to nest and rear their young. Some continue to do so on remote coasts, lonely islands, and sequestered refuges. Until the enactment of a federal law in 1913, supported by treaties with Canada and Mexico, they were not protected.

By that time a few species had become extinct and others, such as the Royal and Gull-billed terns, almost wiped out by periodic raids for the eggs on their nesting colonies. Several species -- notably the egrets and the Roseate, the Least and the Common terns -- slaughtered during nesting seasons to supply the millinery trade with their beautiful plumage, had also been nearly exterminated.

In the latter part of the 19th century and the first decade of this one, women wore big hats adorned with furbelows and feathers. Egret plumes, the wings and breasts of terns, and elegant little birds such as the Least Tern -- stuffed and mounted in jaunty poses -- were in great demand. Public opinion aroused by Audubon societies, and the Plumage Act ended that and saved them.

Many people confuse terns with gulls but, although closely related, they have noticeable differences. Most terns are slim and stream-lined. They are often called "sea swallows" because of their long narrow wings, long forked tails and swift graceful flight. Excepting the chunky gull-billed tern, they have long tapering bills and fly with them pointing downward; whereas a gull' s bill is shorter, hooked at the tip, and in line with the body when flying.

Gulls are more heavily built, with broader wings and square or rounded tails. Both terns and gulls have webbed feet, swim easily, and gulls commonly alight on water to feed or rest. Gulls are valuable as scavengers. Terns prefer live food and seldom aligm on water but plunge headlong into it to capture prey beneath the surface. On the coast of Maine we saw a fishing vessel put out nets and fill her holds with tons of fish where thousands of terns were circling, shrieking and diving into a dense mass of herring driven to the surface by a hungry school of bluefish.

There are about 50 species of terns and nearly all are seabirds but four of them are common in the interior of North America, either as migrants or as nesting birds. The Black Tern is most numerous. It is about 9-1/2 inches long, with a 20-inch wingspread -- slightly larger than a least tern. Its tail is shorter than those of most terns and notched instead of forked. In summer, the upper parts are slate gray but the head, neck and body are black.

At McGinnis Slough and similar areas in the forest preserves it is interesting to watch them zigzag swiftly over the water, capturing insects on the wing, or hovering above shallow places in search of minnows, tadpoles and crayfish. They nest on old muskrat lodges or floating piles of vegetation and lay three eggs heavily marked with dark brown spots and blotches .

Forster's Tern, common as a migrant, occasionally nests on sloughs in this region. About 15 inches in length, it has a long forked tail, pure white under parts and wings, black ear patches on its white head, and an orange bill. The Common Tern, very similar, rarely nests here but is frequently seen during migrations. The Caspian Tern which, like the black, common and least terns, breeds around the world in the northern hemisphere, occasionally stops here when migrating. It is heavy, broad- winged, with a black head, and the largest of this tribe -- 21 inches long, with a 53-inch wingspread.

The Sooty and the Noddy Terns inhabit tropical islands such as the Dry Tortugas west of Key West. The Arctic Tern, abundant in the far north, is famous because some of them migrate to and from the Antarctic -- a round-trip flight of 22,000 miles.


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