134 THE UNIVERSITY OF THE STATE OF NEW YORK 



(a) Lack of fear 



Blackburnian warbler Nu WAS 



Ring-necked pheasant Nu PjR6 



(b) Active defense 



Least' bittern Nu BiL24 



6 Hatching 



On the tip of the upper mandible of the young birds in the 

 shell a small pointed tooth develops which by the twisting of 

 the young bird cuts through the shell and permits the youngster 

 to escape. Ordinarily no help is needed from the old bird but 

 occasionally she gets impatient, especially in the presence of 

 danger, and assists the young one to break the egg. With some 

 species the eggs are always broken in two pieces with very even 

 edges — a cap being cut off from the larger end. As soon as the 

 young have hatched the egg shells are removed or eaten by the 

 old bird. If an egg proves infertile and does not hatch, it may 

 be thrown from the nest or it may be left in the bottom. 



a Normal breaking 



Virginia rail Nu RVS 



Note that the fourth bird is breaking through the shell. 

 Gallinule Nu GcF52 



b Method in grouse family 



Young pheasants Nu PjR4 



Young grouse Nu GuRS 



c Removal of shells and bad eggs 



Pied-billed grebe removing shell Nu GsP4 



Bobolink egg removed Nu Bo4 



The Young 



1 Condition at hatching 



The young of birds at hatching are of two types, precocial and 

 altricial. The grebes, loons, gulls, terns, ducks, marsh birds, 

 shore birds and fowllike birds have precocial young and other 

 birds have altricial young. 



o Precocial 



Their eyes open immediately after hatching and they are 

 clothed in thick down. They are able to run about or swim as 



