Page:The New International Encyclopædia 1st ed. v. 14.djvu/646

NIDIFICATION. 552 NIDIFICATION. trees, or to the deserted burrow of some mam- mal, especially the prairie dog. Parrots, wood- peckers, kingfishers, mouse-birds, todies, and some others lay their eggs in holes in trees, or in earthen banks, with little or no bedding. Humming-birds (q.v. ) build the most delicate and Ijeautiful nests known; and swifts extraor- dinar}' ones, consisting largely of mucilaginous saliva. (See CuiMNEY-SwiKT; Sala.ng.v.nE.) Many song-birds build on the ground, where the nest is more or less cleverly concealed, but the great majority build in trees'or bu.shes. The most remarkable nests built by any birds are those of the .American orioles or hangnests, and more especially of the weaver-birds (q.v.) of Africa and the East Indies. The perfection of many nests for the purposes to which they are put. and the ingenuity, skill, and apparently aesthetic sentiment displayed by man}' birds, long ago led to some study and much speculation. An e.xcellent book was made upon the subject early in the nineteenth cen- tury — Kennie's Architect tire of Bij-ds (London, 1831). He divided his subjects into such classes as ground-ncsters, squatters, and miners; build- ers of mounds, of umbrellas, of domes; masons; carpenters; platform-makers; basket-makers; weavers; tailors; felters; and cementers. This was purely artificial, but did well enough so long as nests and eggs were treated as things separate from the bird itself. About forty years later Wallace included in his book Contribiition.i to Natural Selection (London, 1870) an essay on "A Theory of Birds' Nests," in which he discussed the subject from an evolutionary point of view, showing the analogy between the method of birds and primitive men in meeting their diverse requirements of shelter out of the ma- terials most available. Wallace places birds' nests in two great classes — a functional, not a structural, classification. The first class includes those in which the eggs, young, and brooding parents are not exposed. To this group belong nests that are built in natural covers, such as holes in trees or in banks and cliffs, as well as nests covered by the bird, such as the suspended nest of the American orioles. To the .seccmd class belong the nests of the ordinary type, cup- shaped and open above, so that the eggs, young, and brooding females are exposed. This contrast in method of nidilication. as he believed, cor- related with the color of the female. As he says: '"When both sexes are of strikingly gay and conspicuous colors the nest is of the first class, or such as to conceal the sitting birds; while, whenever the male is gay and conspicuous, and the nest is open so as to expose the sitting bird to view, the female bird is of dull or obscure colors." The comments and criticisms upon this theory by the Duke of .rg-le. by Prof. .. Mur- ray, and by .f. .A. .Mien (Biillclin Xuttall Ornilh. Club, vol. iii., Cambridge, 187S), and by others more recently, show that it is not so universal in its application or fully explanatory as its author considered it. The hypothesis Was re- stated, with improvements, by Wallace, in Dar- winism (New York reprint. 1880). The more recent philosophic view, well sum- marized by riiapnian (Hirrl Life. New York, ISIIS), is that, apart from and above the various considerations already mentioned, the necessity for protection of the eggs and young from physical accidents, loss of heat, and .seizure by enemies is the real motive; and the superior excellence as cradles of the nests of birds of the higher orders is explained by the fact that these orders are 'altricial' — that is, their young are born in a helpless condition, must be cared for by the parents for a considerable time, and hence both old and young need much better and safer quarters than do the 'precocial' birds, whose joung (e.g. chickens) run about at birth and have no need of a nursery. Wallace also treated of the belief formerly prevalent that birds work by instinct and never fliake any improvement during their lifetime in nest-building. He asserted that the chief mental faculties so exhibited by birds are the same in kind as those manifested by mankind in the formation of their dwellings: that is, essen- tially, imitation, and a slow and partial adapta- tion to new conditions. In answer to the ob- jection that it is not so much tlie material as the form and structure of nests that varies, Wallace replied that such diversities may be explained in a great measure by the general habits of the species, the nature of their tools, the materials they can most easily obtain, and diflferences of habitat and needs that niaj- have occurred within the period of existing species, due to changes in climate, the earth's surface, food, and so forth. Birds learn something, doubtless, in regard to the size, structure, and material of the nest of their own species before they leave it. Wallace quotes a numl)er of cases of birds reared in the nests of other birds that sang only the song of the foster parent, learned while in the nest. Then, too, young birds do not always mate with birds of their own age, and the young bird learns nest-building from its moro experienced mate. It is not unisual to see onft bird of a i)air, say an English sparrow, redis- posing the material that the other bird has just put in place. Several observers have stated that young birds build less perfect nests than old birds, and Wallace quotes one instance in which some yoimg chaffinches were taken to New Zea- land and there set free. They built a nest in the new home which showed •'very little of that neatness of fabrication for which this bird is noted in England." It is an oft-repeated observa- tion that the nests of the Baltimore oriole, when built near the h;ibitations of man. (Iifr<'r in shape and structure from those in the wilds where twine and threads are not at hand, and where there is more necessity of concealment from hawks and snakes. The swallows and swifts of all parts of the world are quick to change their nesting places from hollow trees and rocky clitTs or caverns to the porches, barns, and chimneys of men's habitations, anil changes in the style of their architecture follow. The nests of house wrens and purple martins vary with the situa- tions chosen. The orchard oriole may build a shallow nest in stout brancho or deep ones in swaying willows. Many sin)ilar instances of change in form and inaterial might be adduced, "f'hildren and savages imitate before they originate; birds, as well as all other animals, do the same." so when the environment remains constant, the form and constructive material of birds' nests vary little. HiiooDiNo OF Birds. The eggs of birds are hatched by the steady application of warmth for a sufTicient time to matire the embryo to the stage when it breaks from the shell. This