XX 



THE ECONOMIC RELATIONS OF MAMMALS AND BIRDS 



It is probable that all mammals that eat flesh of any sort will devour 

 birds when they are hungry, if they have the opportunity. They are of 

 course more destructive to ground-nesting species, but also easily get 

 young birds of tree-nesting species just after they leave the nest and 

 have not yet achieved dexterity on the wing, and occasionally succeed 

 in capturing adult tree-nesting birds that feed upon the ground, such as 

 robins. 



Swine eat the eggs of both wild birds and poultry and sometimes 

 kill the birds. In cities and about farms the mammals most destructive 

 to wild birds are domestic cats, many of which, though not usually at- 

 tempting to catch adult birds, feel an irresistible impulse to spring upon 

 every young bird seen fluttering on the ground in the effort to fly. The 

 domestic dog also sometimes catches wild birds and an occasional well 

 fed individual acquires the habit of killing chickens and turkeys, not 

 for food, but from sheer blood-lust, just as others acquire the sheep- 

 killing habit. 



Other members of the cat and dog families (Canidae and Felidae) 

 are definitely known to kill birds and probably all do so to some extent. 

 Audubon and Bachman long ago remarked that the wildcat "makes 

 great havoc among the chickens, turkeys and ducks of the planter." 1 

 Dixon found that bird remains constituted 3.1 per cent of the contents 

 of 1 1 8 wildcat stomachs examined by him. 2 Foxes sometimes kill birds, 

 though their preference is for rodents. In the lair of one were found 

 the remains of 76 short-eared owls (8 adults) and a number of grouse, 

 ducks, plover and curlew, besides rats and voles. 3 



The brown house rat eats wild birds and their eggs and is said to 

 "kill more young chickens than any other animal." 4 Some species of 

 squirrels and chipmunks, especially the red squirrels, are known to 

 kill young birds, but do more damage by eating the eggs of both tree- 

 nesting and ground-nesting species. 6 Muskrats take some wild birds, 



1 Quoted in Howell, N. Amer. Fauna, No. 45, p. 42, 1921. 



2 Dixon, Journ. Mammalogy, vi, 36-38, 1925. 



8 Fisher, Yearbook U. S. Dept. Agric. for 1894, p. 225, citing Adair, Annals 

 Scottish Nat. Hist., Oct., 1893. 



4 Fisher, Yearbook U. S. Dept. Agric. for 1908, p. 193. 



"Thorns, Are squirrels bird enemies? Bird-Lore, xxiv, 206-207, 1922. Stoddard, 



120 



