_Size._--Name birds as large as a robin or larger, nearly as large, half as large, much smaller. _Colors._--Which sex is more brilliant? What advantage are bright colors to one sex? What advantage are dull colors to the other sex? Which have yellow breasts, red patch on heads, red or chestnut breasts, blue backs, black all over? _Habits._--Name the birds that walk, jump, swim, live in flocks, sing while flying, fly in undulations, in circles, have labored flight. Such books as Wright’s “Birdcraft” (Macmillan, N. Y.), Clark’s “Birds of Lakeside and Prairie” (Mumford, Chicago), and Pearson’s “Stories of Bird Life” (B. F. Johnson, Richmond), will be of great help. The last book is delightfully written, and is one of the few treating of bird life in the South. =Economic Importance of Birds.=--Farmers find their most valuable allies in the class _aves_, as birds are the deadliest enemies of insects and gnawing animals. To the innumerable robbers which devastate our fields and gardens, nature opposes the army of birds. They are less numerous than insects and other robbers, it is true, but they are skillful and zealous in pursuit, keen of eye, quick, active, and remarkably voracious. The purely insectivorous birds are the most useful, but the omnivorous and graminivorous birds do not disdain insects. _The perchers and the woodpeckers should be protected most carefully._ The night birds of prey (and those of the day to a less degree) are very destructive to field mice, rabbits, and other gnawing animals. Some ignorant farmers complain continually about the harm done by birds. To destroy them is as unwise as it would be to destroy the skin which protects the human body because it has a spot upon it! It cannot be repeated too plainly that to hunt useful birds is a wrong and mischievous act, and it is stupid and barbarous to destroy their nests. [Illustration: FIG. 311.--SCREECH OWL (_Megascops asio_). =Question:= Compare posture of body, position of eyes, and size of eyes, with other birds.] [Illustration: FIG. 312.--GOSHAWK, or chicken hawk.]