CHECKS UPON INCREASE OF USEFUL BIRDS. 355 
some States farther west, and that they are not numerous 
enough to fully control the insects on which they feed. 
It is certainly desirable, then, to take measures to increase 
the number of useful birds, and any inexpensive means of 
accomplishing this end is worthy the most careful consider- 
ation of thoughtful people. 
‘When one is asked what controls the numbers of birds, 
he finds himself at a loss for a ready answer. There are 
many well-understood checks upon their increase; others 
are more obscure. We can understand, for example, why 
the larger game birds and shore birds have decreased in 
numbers; but it is difficult to see why the Dickcissel or 
Black-throated Bunting has disappeared from the Atlantic 
seaboard and is now seldom found east of the Alleghanies, 
why the Red-headed Woodpecker has so nearly disappeared 
from Massachusetts, or why certain resident species as well 
as certain migratory species are common one season and 
uncommon the next. 
To effectually protect birds we must first understand the 
chief causes of mortality among them. Comparatively few 
wild birds die from disease or old age. Most of them per- 
ish from lack of food, the severity of the elements, or the at- 
tacks of their enemies. The destruction of birds by storms, 
great and widespread as it is, probably never occurs over 
regions extensive enough to utterly exterminate any species. 
Their destruction by starvation and cold is usually coextensive 
only with the area of severest storm. Under normal condi- 
tions the decimated species usually repopulate the country in 
afew years. Many young birds are killed by storms in the 
nesting season. Many migrating birds are blown into the 
sea and drowned. Fortunately for the birds, they are ordi- 
narily enabled by migration to avoid the severity of winter ; 
but they are unable in this way to escape the destructive 
agencies set at work by man along their lines of migration. 
In annual, perennial, widespread, and complete bird destruc- 
tion, man takes the lead among all other forces of nature. 
1905; and as copies of this report— The Decrease of Certain Birds and its 
Causes; with Suggestions for Bird Protection —can be obtained of the secretary 
of the Board at the State House, its conclusions will not be reiterated here. 
