No family of birds is more difficult for a beginner to identify than the warblers. Reasons for this fact are various. In the first place, warblers are small and agile, and usually inhabit treetops, where it is hard to see their plumage. The number of the species is large,—155 species are known, 74 of which are found in North America, and 55 in the United States alone. Some of the males wear a “Joseph’s coat of many colors”; some of the females are so different from their mates as to puzzle an observer, and the young birds frequently differ from both parents. Then, too, most warblers are not gifted songsters, but utter only a weak trill. A number of them are seen only during their migration to northern woods; they linger too short a time to become more than passing bird-acquaintances.

Warblers are insectivorous and do not arrive until the earth teems with insect life. Most of them depart for the South as soon as insects begin to decrease in number or disappear. They are very shy and migrate at night.

Many are the disasters that befall them when they journey near the sea-coast. In Dr. Wells W. Cooke’s article entitled “Our Greatest Travelers” are the following statements: “It is not to be supposed that these long flights over the waters can occur without many casualties, and not the smallest of the perils arises from the beacons which man has erected along the coast to insure his own safety. ‘Last night I could have filled a mail-sack with the bodies of little warblers which killed themselves striking against my light,’ wrote the keeper of Fowey Rocks lighthouse, in southern Florida.

“Nor was this an unusual tragedy. Every spring the lights along the coast lure to destruction myriads of birds who are en route from their winter homes in the South to their summer nesting-places in the North. Every fall a still greater death-toll is exacted when the return journey is made. A red light or a rapidly flashing one repels the birds, but a steady white light piercing the fog proves irresistible.”[136]

Few people realize the great good done by warblers. Mr. Forbush says that in migration they seem to possess enormous appetites. A Hooded Warbler was found to catch on the average two insects a minute or one hundred and twenty an hour. At this rate the bird would kill at least nine hundred and sixty insects a day, in an eight hour working day!

Dr. Judd reported a Palm Warbler that ate from forty to sixty insects a minute. In the four hours he was under observation he must have eaten nine thousand, five hundred insects. Mr. Forbush says that he has seen warblers eating from masses of small insects at such a rate that it was impossible for him to count them.[137]