BIRDS OF NEW YORK 51 



not be true of the Red-winged blackbird, Crow blackbird, the woodpeckers 

 and many others, but the accounts given by early writers of the tremendous 

 multitudes of "maize thieves," as the blackbirds were called, create a 

 greater impression because the birds were concentrated about the few 

 plantations, whereas now they are scattered over thousands of square 

 miles which formerly were covered with forests. 



The general law of variation in abundance seems to be as follows. Birds 

 which prefer the open country begin to increase as the forests are cut off, 

 and many which live in the forests themselves increase as long as the 

 clearings are few and scattered. As the cultivation of the country pro- 

 gresses and a large percentage of the forests has been cut off, the hawks, 

 owls, grouse, jays, Pileated and Hairy woodpeckers, tanagers and many 

 wood-warblers and thrushes decrease in number. When the swamps are 

 drained there are fewer nesting places for snipe, rails, bitterns and Marsh 

 wrens. As the pasture and meadow lands increase in area, birds like the 

 Bobolink, Meadowlark, Vesper sparrow, Killdeer and Bartramian sand- 

 piper find favorable nesting places and increase. 



But as the modern style of agriculture develops, new dangers arise to 

 threaten the field birds. Late plowing and extensive cultivating and 

 early mowing destroy great numbers of eggs and young birds. A high 

 stage of agriculture is likewise accompanied with danger from the spraying 

 of fruit trees and potato plants, as birds are often killed by eating cater- 

 pillars which have been poisoned. The cutting of all dead limbs and trees 

 also destroys the nesting sites of flickers. Downy and Red-headed wood- 

 peckers, chickadees, wrens and bluebirds. On many well kept farms, 

 also, the barns are so tightly closed that swallows are unable to gain entrance. 

 Thus in many ways the increase of native birds is discouraged, unless arti- 

 ficial means is taken to counteract the evil by such methods as erecting 

 boxes and woodpecker stubs, cutting swallow-holes in the barn, cultivating 

 and plowing around the nests, and watching out for the young birds when 

 mowing. 



In thickly settled districts the danger to many species is further increased 

 by the abundance of telegraph and telephone wires, electric lights, plate- 



