Nests and Eggs of Birds 1 1 



prepared from his knowledge of the known differences in the sizes of birds pro- 

 ducing them, yet there are noticeable surprises even in this respect. But the 

 attempt to account for the striking differences in shape, color, and markings of 

 eggs seems an almost hopeless one, yet such attempts have been made, though, it 

 must be confessed, with varying degrees of success. Theoretically we may be 

 justified in presuming that the lowest of existing birds, that is those that are 

 supposed to approach most closely to their reptilian ancestors, should produce 

 eggs or have habits of nidification showing the closest approach to the reptiles. 

 An examination of the facts, however, shows that this relationship is capable of 

 demonstration to a limited degree only. In the first place, it appears that much 

 is still to be learned regarding the oology of existing reptiles. Broadly speaking, 

 the eggs of all reptiles are white in color and spherical or ellipsoidal in shape. 

 Nothing is at present known regarding the eggs of either the ancient reptilian or 

 avian ancestors of our birds, although, as Shufeldt has suggested, it is by no 

 means impossible that such remains may sometime be found, especially those of 

 the Toothed Birds. Fossil eggs of turtles have been obtained, as well as fossil 

 or subfossil eggs of a few species of birds, but they throw little or no light on the 

 question at issue. It is, then, from this hypothetical starting-point that all the 

 marvelous diversity observable in the eggs of living birds has been developed, 

 but the steps by which it has been accomplished are, and must perhaps remain, 

 obscure. Natural selection has doubtless played a most important role, though 

 the "whys and wherefores" are far from being satisfactorily answered. There 

 are certain salient groups of facts that stand out boldly, yet the exceptions are so 

 numerous and marked as to prevent establishing any adequate chain of cause 

 and effect. Thus practically all birds that nest in holes, such as the Woodpeckers, 

 Kingfishers, Bee-eaters, Rollers, Hornbills, Barbets, Puff-birds, Trogons, 

 Toucans, Parrots, Parakeets, and Swifts, lay white eggs, yet the coordinate 

 groups of Owls, Hummingbirds, and Pigeons, that build an open nest, also lay 

 white eggs, while many birds that habitually nest in holes lay spotted or even 

 richly colored eggs. Again, it is often possible to trace a marked similarity in 

 pattern of coloration throughout nearly all the species of a whole natural family, 

 or a large genus, but for which "the conditions of environment offer no explana- 

 tion, since it as often occurs in cosmopolitan groups as in those of local distribu- 

 tion, and which, in the present state of our knowledge, seems wholly inexplicable." 



Theory of Birds' Nests. So, also, are we without an adequate theory of 

 birds' nests. "Why the thousands of species of birds," says Dr. J. A. Allen, 

 "build each a peculiar nest, differing more or less in situation and architecture 

 from those of all other species, is a question which has yet received no satisfactory 

 answer. As a rule the nest, including its location, the materials and manner of 

 its constructure, is as distinctive of the species as the number, size, form, and color 

 of the eggs, or, in some instances, as any fact in its history, not excepting even the 

 details of structure and coloration of the bird itself. Why this is so we can perhaps 

 explain when we can satisfactorily account for the diversity of song that is scarcely 

 less a scientific characteristic." 



The attempt has been made to explain it on the ground of a connection bet ween 



