16 BIRDS 



twenty-four hours), are of greater value than the seniors. 

 Even seed-eating birds feed insects to their nestlings: an 

 indigo buntingmother does not hesitate to ram a very large 

 grasshopper down her very small baby's throat after she 

 has nipped off the wings. 



Partnerships in Nature 



Just as many insects have resorted to curious and in- 

 genious devices to avoid the birds' attention, so many 

 trees, shrubs, and plants, with ends of their own to be 

 gained, take great pains to attract it. Some insects mimic 

 with their coloring that of their surroundings: one must 

 look sharp before discovering the glaucous green worm on 

 the glaucous green nasturtium leaf. Some, like the milk- 

 weed butterfly, secrete disagreeable juices to repel the 

 birds, and other butterflies, which secrete none, fool 

 their foes by bearing a superficial resemblance to it. 

 Others, like the walking-stick, assume a form that can 

 scarcely be distinguished from the objects they frequent. 

 With what pains does the caterpillar draw together the 

 edges of a leaf and hide within it, sleeping until ready to 

 emerge into its winged stage, if by chance a pair of sharp 

 eyes does not discover it at the beginning of its nap, and 

 a sharper beak tear it ruthlessly from the snug cradle! 

 Children who gather cocoons in the autumn are often dis- 

 appointed to find so many already empty. They forget 

 that thousands of hungry migrants have been out hunting 

 every morning before they left their beds. No cradle yet 

 woven is too rough for some bird to tear open for the 

 luscious, fat morsel within. To the Baltimore oriole 

 looking for a dinner, the strong cocoon of the great ce- 

 cropia moth yields one as readily as another; and I have 



