22O Descriptive Zoology. 



the wings ; but the ducks shed their wing quills all at once 

 and for a time are unable to fly. Some birds shed the 

 claws, and the puffin sheds the outer covering of the beak. 



Migration of Birds. Comparatively few of the birds 

 that we see during the year reside with us permanently. 

 If one makes a list of the birds that remain through the 

 winter, he misses many of his summer acquaintances. The 

 crow, jay, nuthatch, chickadee, some of the woodpeckers, 

 several sparrows, the hawks and owls, and a few others 

 are left, when the rest have flown southward. Why do 

 they go ? The common answer is, " Because they cannot 

 endure the cold." But if one examines the feathers he 

 finds little difference between the robin and the jay, or the 

 bluebird and the sparrow. It is chiefly a question of food. 

 The robin and the bluebird live mostly on insects and 

 worms. As winter approaches these birds can no longer 

 find this sort of food in northern latitudes, and they seek 

 a warmer climate, not so much because they cannot stand 

 the cold as because insects and worms cannot stand the 

 cold. Woodpeckers are insectivorous, yet remain ; but 

 they can get the larvae from the trees about as well dur- 

 ing the winter as in the summer. The large majority of 

 the birds that remain with us during the winter are either 

 seed-eating birds, like the grouse and sparrows, or car- 

 nivorous, as the hawks and owls. Some are omnivorous, 

 like the crows and jays. Some birds, such as the swal- 

 lows, are very regular in the times of their migrations. 

 Others are irregular, and some birds migrate or not, 

 according to varying conditions. We must keep in mind 

 the bird's marvelous power of flight ; in a short time he 

 can cover a very great distance. 



Parasitic Birds. Perhaps the most common example 

 of the parasitic habit is seen in the common cowbird. 



