4 GEOGRAPHICAL RACES.

of climate upon the color and size of birds;* (6) the relation of a bird’s color to its haunts and habitsflr Besides these general subjects which enter into our study of the life-history of every bird, we have the special instances of intelligent adaptation to changed conditions of life, and. most interesting of all, the relation between structure and habits, or the part played by a bird‘s habits in determining the form of its bill, feet, wings, and tail. Tints the Crook—billed I’lover of New Zealand turns over or probes under stones and shells in search of food, not because its crooked bill makes an excellent lever or probe, but it has acquired a crooked bill through this habit. Again, the Gallinules of certain islands in southern seas are flightless, not because their wings are too small to support them, but because after having,r flown to these islands they had no further use for wings. which in time, through dis- use, became so small that the birds have lost the power of flight. In other words, it is not because their wings are small that they do not fly, but because they do not fly their wings are small.

But to enlarge upon these problems which confront the philo- sophic ornithologist would require a Volume. It is important, how- ever, that the student should have in the beginning at least a general idea of the effect of climate on the size and color of birds and the migration of birds. The first is well illustrated by our Bob—white or Quail. In New England. at the northern limit, of its range, it is a fine, large bird with a light-brown back and a white breast narrowly barred with black. As we proceed southward it becomes smaller. the brown is of a deeper shade. the black bars of greater extent. Finally, when we have reached the humid region of southern Florida, the minimum in size is attained. the back is dark. rich chestnut barred with black, and the breast is almost wholly black. No one who compared this small. dark Florida Quail with the large. pale Quail of New England would consider them the same species. lint on examining a series of Quails from all the Atlantic States one sees how g: 'adnally this change in color and decrease in size occurs. and that nowhere would it be possible to draw a line separating the two extremes. They are species in process of formation still connected by a chain of natural links.

()ri'iithology presents many similar cases. They illnst 'ate two laws in the evolution of animals—deer*ase in size southward and greater

*Ri-ad Part III of Dr. I. A, Allen‘s Mammals and “'inter Birds of East Florida, Bull, Mus. Comp, )tll.. vol, ii. No. 3. (‘mnbridgin 1871.

+Consnlt Ponlton‘s Colors of Animals :1). Appleton s; (‘0. 189(1): Berl- dard‘s Animal (‘oloration (Macmillan K’ (‘o.): Keeler‘s Evolution of the Colors of North American Land-birds (Occasional Papers of California Academy Of Sciences. iii, 18931 ; also reviews of last two works in The Auk. x. D493, pp. 18!)» 199, 373i380.