THE BIRDS 



421 



be thrust down a slender hole to stick insects and bring them out to eat. 

 One of the woodpeckers, the yellow-bellied sapsucker, has become harm- 

 ful, for it has discovered that it can dig holes in trees and sap will fill 

 the holes. Then it can suck this sap out as its food. 



>to by Chas. 



Schwartz 



Fig. 27.12. 



A red-headed woodpecker at the entrance to its nest. Note how the tail 

 is used as a brace to give the bird more power for its pecking. 



The Cowbird. Cowbirds are one of the few birds that are parasitic. 

 They lay their eggs in other birds' nests and allow foster parents to feed 

 and care for their young offspring. The female cowbird spends most 

 of her time during the nesting season searching for recently built nests 

 in which the clutch of eggs is not complete and the parents have not 

 yet started incubating. When she finds such a nest she picks up one of 

 the eggs in her bill and flies away with it. Early the next morning, 

 usually before sunrise, she slips into the nest and replaces the missing 

 egg with one of her own. When the rightful owner of the nest comes 

 to lay another egg, she finds the number of eggs unchanged and usually 

 does not notice that one of the eggs is different in size and color. There 

 is an interesting hypothesis to explain this odd practice of the cowbird. 

 The old name for this bird was buffalo-bird, because it always fed around 

 the great herds of American buffaloes that once inhabited our great 

 plains. Since these buffaloes were great wanders, the cowbirds often 

 found themselves far from their own nest when the time came to lay an 



