Only a few close observers of bird life know them well. Warblers are important in nature and to man. 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. Some feed in the tops of the taller trees, where they flit about incessantly. 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.
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.