88 THE CONDOR Vol. XIX 



ure out the biological reasons for the various developments in nidification are 

 comprised in a few pages of printed matter. A. R. Wallace has given an interest- 

 ing theory of the relation of the nest to the coloration of the species building it, 

 in his "Theory of Birds' Nests" (Journal of Travel and Natural History, 1868). 

 This has been discussed and criticised by Dr. J. A. Allen, in the Bulletin of The 

 Nuttall Ornithological Club. A few limited and cursory discussions of various 

 phases of the subject are given in various general works such as Knowlton's 

 "Birds of the World", but no extended study of the subject has been made. 



Just why the individuals of one generation of a given species in the animal 

 kingdom should occupy themselves in any manner with the rearing of the suc- 

 ceeding generations is a philosophical enigma, for after the production and fer- 

 tilization of the egg no physical necessity of their own is satisfied by it. Never- 

 theless we find the beginnings of such care even among the lowest animals. 



Nidification first appears in the vertebrates among the aquatic forms, for 

 among fishes the little stickleback and the pugnacious sunfish guard their nests 

 with great fearlessness, while the humble bullhead, after the eggs are hatched, 

 may be seen leading his dusky young about as they learn the business of fish life. 

 Fish nests are usually very simple affairs, being seldom more than shallow basins 

 in the stream bottom, but when we get among the higher vertebrates we find 

 more ambitious structures. For among all vertebrates the nest has reached its 

 most elaborate development with man, though in the other great group of warm- 

 blooded vertebrates, the birds, it has reached a development in which many nests 

 show a wonderful ingenuity and exquisite care in construction. 



The nesting habit among birds is probably anticipated by the nesting habits 

 which are found among reptiles, as from the ancient reptilian group of Dinosaurs 

 have probably arisen our modern birds. The nesting habits of the higher modern 

 reptiles and some of the more primitive birds are so similar that they can be said 

 to bridge over the gap from the slovenly nidification of the average indifferent 

 reptile to that solicitous care of the young characteristic of the highest birds. 

 Many of the modern snakes deposit their eggs in holes in the ground or in the 

 soft wood of rotten stumps, and turtles dig jug-like holes in the sand. Some 

 tropical alligators deposit their eggs in warm sandbanks, while those found in the 

 cooler latitude of the southern states bring together a mass of rotting vegetation, 

 by the warmth of which the eggs are hatched, after which the young are guarded 

 for a time by the mother. Now this method of nesting occurs among some of the 

 lower birds, though here it is a reversion from, or more probably a special devel- 

 opment of, the general bird type. The interesting fowls which have this primi- 

 tive nesting habit are the Megapodes of the Australian region. Of these, the Aus- 

 tralian Brush Turkey (Catheturus lathami) rakes together a pile of decaying 

 leaves and rotten wood, and in this mound at intervals deposits its eggs, which 

 are incubated by the heat from the decomposition of the nest materials. Other 

 members of this same curious group deposit their eggs in the warm sands of the 

 sea shore, where they are left without further care. 



Similar to this were probably the beginnings of the nesting habit among 

 birds. Careful guarding of the eggs early developed into a definite period of in- 

 cubation, which was made possible by the high temperature of the body. The de- 

 velopment of the four-chambered heart meant the possibility of the great devel- 

 opment of the brain, as this delicate organ was no longer poisoned by quantities 

 of venous blood ; then, with this increase in brain power, could come the dexterity 

 and ingenuity displayed by the average bird in constructing his home. 



