museum specimens. Not until we have the patience and skill to watch and to find 

 the most deadly enemies which threaten the nests and eggs of birds, their number 

 and modes of attack, can we hope for successful solutions to the thousand and 

 one problems which offer themselves. What we know in respect to eggs is frag- 

 mentary and rests on so slight a degree of proof that every theory is attacked and 

 reattacked in turn. 



Supposing that the eggs of the early forms of birds were round — that being 

 the most typical form of a single cell — we find many variations in shape among 

 the eggs of living species. Many of the eggs which are laid in hollow trees still 

 retain the primitive spherical form, perhaps an advantage in keeping the eggs in a 

 close group in the center of the floor of the cavity. 



So characteristic of the eggs of birds is the pear shape — one end blunt and 

 narrowing to the other — that they have given to it its name — oval. In the eggs of 

 certain sea birds which breed on the narrow ledges of perpendicular cliflfs this 

 oval shape is carried to an extreme, and apparently for an excellent reason, 

 mechanical, but of inestimable value to the birds. Eggs laid in such positions are 

 of course especially exposed to danger from the wind or from some sudden move- 

 ment of the birds, which generally nest very close together. Were it not that the 

 eggs, on account of their peculiar shape, describe an arc of very small diameter 

 when they roll, doubtless a far greater number would roll ofif and be dashed down 

 upon the rocks below. Among the plovers, sandpipers and phalaropes we again 

 find a peculiarly pronounced pyriform shape of egg, serving in these instances a 

 very apparent and useful end. These birds almost invariably lay four eggs, which 

 are of large size in comparison with the birds, and their shape allows them to be 

 fitted closely together, each forming one of the four segments, their points all but 

 meeting in the center. Thus the little body of the parent is large enough to cover 

 them all, which would be impossible were the eggs arranged at random. The 

 eggs of grebes are peculiar in having both ends alike. 



The number of eggs which a bird lays has been found to bear a definite rela- 

 tion to the amount of danger to which the species is exposed ; but when we come 

 to the water birds — the rails, gallinules, ducks and geese — we find an extensive 

 group whose nests average a dozen eggs in each set. Explanations are ready for 

 this ; the birds themselves are exposed to unusual peril, from weather as well as 

 from active enemies, since they mostly emigrate to the extreme North and nest 

 in the edges of marshes, where the sitting birds, eggs and young are all subjected 

 to freezings, floods and countless marauders that depend largely upon them for 

 food during the Arctic summer, so that a heavy annual recruiting must be made 

 to repair losses. Few birds are liable to so many misfortunes and mishaps as the 

 water fowl, except perhaps the big and pugnacious swans, who can take better 

 care of themselves, and lay only five eggs or fewer. The long-legged wading 

 birds also, such as the storks, ibises, herons and the like, are fairly safe in breeding 

 season, because they nest in trees, as a rule, and consequently we here find only 

 two to four young in the annual brood ; so with the snake birds. 



668 



