46 The Bird 



summer, or may drop out as soon as begins the hard 

 work of building the nest or feeding the young, with which 

 labor they might interfere. 



To return for a moment to the fall moult. If a spar- 

 row or lark should shed all of its large wing-feathers 

 simultaneously, it would have slight hope of ever living 

 long enough for new ones to grow out again. If such 

 defenceless birds were compelled to hop helplessly along 



FIG. 28. Wings of English Sparrow, showing two feathers of each wing being 



moulted simultaneously. 



the ground, weasels and cats would be able to catch 

 hundreds of them without effort. This is avoided in all 

 land birds by the moulting of only a pair of primaries, 

 as the large flight-feathers are called, at a time, one from 

 each wing. This process usually starts with the pair 

 farthest from the front of the wing, and the second pair 

 does not fall out until the first pair of new feathers is 

 nearly of full size. Thus all danger of a crippled flight 

 is avoided. 



One of the most interesting phases of Nature is the 

 way she provides for exceptions to what we are pleased 

 to call her laws. Some birds, unlike those mentioned 



