FACTORS IN ANIMAL LIFE 
varying degrees of excellence — that is, first nests in 
the spring. The second nest of any species is likely 
to be a more hurried and incomplete affair. Some 
species are at all times poor nest-builders, as the 
cuckoos and the pigeons. Other birds are good nest- 
builders, as the orioles, the thrushes, the finches, 
the warblers, the hummingbirds, and one never finds 
an inferior specimen of the nests of any of these 
birds. There is probably no more improvement in 
this respect among birds than there is among insects. 
Ihave no proof that wild birds improve in singing. 
One does not hear a vireo, or a finch, or a thrush, or 
a warbler that is noticeably inferior as a songster 
to its fellows; their songs are all alike, except in the 
few rare cases when one hears a master songster 
among its kind; but whether this mastery is natural 
or acquired, who shall tell ? 
What birds learn about migration, if anything, 
TI do not see that we have any means of finding out. 
It has been observed of birds reared under artificial 
conditions that the young males practice a long time 
before they sing well. That this is true of wild birds, 
there is no proof. What birds and animals learn by 
experience is greater cunning. Does not even an old 
trout know more about hooks than a young one? 
Birds of any kind that are much hunted become 
wilder, even though they have not had the experience 
of being shot. Ask any duck or grouse or quail 
hunter if this is not so. Our ruffed grouse learns to 
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