The Audubon Societies 245 



complement is subject to but little variation with each species, it is not at 

 all indicative of the fecundity of the bird, for, when the nest is broken up, 

 birds will ordinarily lay again and sometimes will continue laying throughout 

 the season until they are finally successful in raising their young. The case 

 of a Flicker that laid 71 eggs in 73 days has been cited many times, and it is 

 not uncommon now-a-days to develop a strain of domestic hens that will lay 

 over 200 eggs in a season, though if the eggs are not removed, they ordinarily 

 stop laying and begin to incubate when they have laid fifteen to ".twenty. 

 The shape of birds' eggs varies from those that are quite long'and slender, 

 through those that are oval or sharply_pointed, tothose that are nearly spherical. 



EGGS OF THE OSTRICH, HEN. AND HUMMINGBIRD, SHOWING EXTREMES IN THE 

 SIZE OF EGGS OF LIVING BIRDS 



Those of the Hummingbird and Ostrich show extremes of shape as well as size. 

 The large eggs of shore-birds are sharply pointed, so that they will fit together 

 like the pieces of a pie and be more easily covered by the incubating bird. 

 Those of the Murres are pointed for another reason — to keep them from blow- 

 ing off the cliffs where they are laid without pretense of a nest. The ordinary 

 shape of birds' eggs is oval, a shape which keeps them from rolling freely and yet 

 which makes them fit together and be most comfortable for the incubating bird. 

 The parts of the bird's egg are the same as those of the egg of the domestic 

 fowl or the same as those of any animal, for that matter, consisting of the yolk, 

 the albumen, and the shell, with their respective membranes. The yolk is 

 formed entirely in the ovary of the bird, the albumen in the upper two-thirds 

 of the oviduct, and the shell in the lower third, the pigment ordinarily being 

 the last thing added, though with some birds, like the Emu, the successive 

 layers of shell are each pigmented and colored differently from the exterior. 



