388 PRACTICAL ZOOLOGY 



Squirrels. Some individual squirrels are habitual nest 

 robbers. This includes all species, but the red squirrel is the 

 worst culprit. Where squirrels have the nest-robbing habit, 

 they may do more harm among birds than any other mammal 

 except the cat. They are active, can climb to almost any bird's 

 nest, and can defend themselves when attacked by the parent 

 birds. Red squirrels and gray squirrels will rob nests either on 

 the ground or in trees, taking eggs or young as they find them. 

 The chipmunk usually molests only those nests that are on or 

 near the ground. 



Rats and Mice. Rats and mice kill some birds. Probably 

 the tree-climbing, white-footed or deer mouse is one of the great- 

 est enemies that birds have among these smaller mammals, 

 but under natural conditions it is held in check by owls. 



Hawks. A very few species of hawks are probably the most 

 destructive native natural enemies of birds. All other hawks 

 kill comparatively few. The sparrow hawk, a great insect killer, 

 kills fewer birds than the others, and is regarded as a friend to 

 the farmer ; but there are three species of pernicious hawks : 

 the American goshawk, the Cooper's hawk, and the sharp- 

 shinned hawk. The goshawk is an uncommon or periodical 

 winter visitant, but the other two are fairly common, and in- 

 dividually are probably the most destructive of all the natural 

 enemies of birds. They are slaty or bluish above, with rather 

 short, rounded wings, and long tails. When flying at any 

 height, they progress by alternate periods of flapping and soar- 

 ing. They may be known by their shape and by their manner 

 of flight. 



Owls. All the owls kill birds, but most species kill but few. 

 They live mainly on mammals, particularly rodents like mice, 

 rabbits, and hares, on the increase of which they constitute an 

 effectual check. 



Crows and Jays. The crows, jays, and magpies have ac- 

 quired a world- wide reputation as nest robbers. The common 

 crow and the blue jay manage to live up to their reputation. 



