BIRDS OF NEW YORK STATE 



137 



c Defense of nest and young 



The instinct of the parent to defend the young increases as the 

 latter develop and reaches its highest point as they are leaving 

 the nest. Birds have various vi^ays of responding to the approach 

 of an enemy. Some feign a broken wing, others dart at the 

 enemy, or present a ferocious appearance, while the vast majority 

 merely utter cries of distress which brings out all the other birds 

 of the neighborhood. 



(1) Cries of distress 



Robin Nu Ro74 



(2) Darting at enemy 



Black tern Nu TfB9 



Bittern Nu BiA 



(3) Feigning broken wing 



Killdeer Nu Ke8 



d Nest sanitation 



Most birds keep the nest scrupulously clean, the excrement 

 being removed after each feeding. To facilitate this nature 

 incloses it in a mucous sheath so that it can be easily carried. 

 Some birds, however, regularly devour it. Fish-eating birds are 

 rather unclean and the tops of the tree in a heronry are frequently 

 killed by the chalky excrement. 



(1) Normal 



Red-winged blackbird inspecting 

 Red-winged blackbird cleaning 

 Red-winged blackbird with excrement 

 Meadowlark 



(2) Unclean 



Great blue heron 



3 Growth of feathers 



a General method 



The feathers of a bird are not borne over the entire surface 

 of the skin but on well-defined lines or tracts with bare spaces 

 between that are covered by the overlapping of the feathers. 

 When the real feathers begin to develop, they are inclosed in 

 stiff, bluish sheaths which make these feather tracts very con- 

 spicuous. With most birds these feather sheaths, or "pin 



