Forest Preserve District of Cook County, Illinois
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Spring Warblers
Nature Bulletin No. 190-A   April 30, 1965
Forest Preserve District of Cook County
Seymour Simon, President
Roland F. Eisenbeis, Supt. of Conservation

Maytime, to the bird lover, is warbler time, when swarms of these colorful little "butterflies of the bird world" stop briefly to feed and rest as they migrate, in wave after wave, toward their nesting grounds. Some of them come from Central America; some from Brazil and Peru. Some of them will nest as far north as stunted trees and shrubs occur in Alaska, northern Canada and Labrador. A few of certain kinds will nest here, but most of them are here today and gone tomorrow. Only a few close observers of bird life know them well. Most folks call them "wild canaries" and let it go at that.

Warblers are important in nature and to man. We are indeed fortunate that they come when they do, in countless numbers; and that they travel only at night, stopping to feed and rest during the day. For it is in May, when the flower buds and leaf buds are opening on our shrubs and trees, that myriads of insects are emerging to gorge themselves upon the tender juicy blossoms, twigs and leaflets. And all during May, these insects are searched for and eaten by the warblers: birds tailored for the job, which, as Dr. E. Laurence Palmer said, "must be done by birds so small that their weight will not break the finer twigs; birds small enough to probe the little places; birds that are active, hungry and numerous. .

Some feed in the tops of the taller trees, where they flit about incessantly. Others are usually found in the shrubs or smaller trees; including at least one that seems to prefer fruit trees in blossom. Some may be seen anywhere from the treetops down to dense brush near the ground; including one that feeds chickadee-fashion, hanging upside down near twig ends, picking insects from the undersides of leaves. The Black and White Warbler, one of the first to arrive, searches up and down the tree trunks and larger branches like a brown creeper or a nuthatch. Some kinds prefer vegetation near streams, ponds and marshes. And there are a few -- notably the Ovenbird, and the tail- wagging Palm Warbler -- that do all or most of their feeding on the ground.

A few species eat seeds and small berries, but insects in the egg, larva, pupa and adult stages make up most, if not all, a warbler's diet. Some are expert at catching gnats, flies, moths and other insects on the wing. Thus the warbler tribe is of tremendous importance in controlling plant lice, scale insects, caterpillars, cankerworms, moths, bugs, beetles and a host of other injurious insects.

Of 38 kinds observed in spring migrations thru the Chicago region, only 4 or 5 are abundant. About 20 more are common or fairly common. A few kinds, especially the Myrtle Warbler, begin to appear in April; a few kinds do not arrive until some time late in May and are still here in June; but there are three or four days, usually about May 15, when it is possible to see more warblers and more kinds of warblers than at any other time. To do so, you should get up at daybreak. And to study them you need a pair of good binoculars, Roger Tory Peterson's "Field Guide to the Birds", and the "Audubon Bird Guide (Eastern Land Birds)". The male warblers are all singing joyously when they arrive here in spring, and if you can learn to recognize the distinctive calls of the various species, it will help you to find them and distinguish the adult males from the yearlings and the females which have a different and more modest plumage. When they return in the autumn, they do not sing and the males of most species appear to be different birds, having molted and assumed a plumage closely resembling that of the female.

Woodlands bloom and warblers warble in the month of May.

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