188 FRIENDS WORTH KNOWING. 
The logic of the case is simple; birds will assemble 
chiefly where food for themselves and their young is in 
greatest abundance, and where they are least exposed to 
enemies. These two prime conditions of prosperity, with 
many favorable concomitants, man’s art supplies to the in- 
sessorial birds, which, on the other hand, suffer little direct 
injury from his contact. Yet some species seem little af- 
fected by the civilizing of the country, either in numbers 
or habits, while others increase rapidly on the first settle- 
ment of a region, and then decrease again. Of this class 
are the prairie-hen (Cupidonia cupido) and the mallard. 
“They find abundance of food in the corn and wheat 
fields; while the population is sparse and larger game so 
abundant, they are hunted very little; but as the popula- 
tion increases they are gradually thinned out, and become 
in some cases exterminated. Other birds, as the quail, are 
wholly unknown beyond the frontier, and only appear af- 
ter the country has been settled a short time. Still others, 
woodland species, appear in regions where they were never 
known before, as groves of trees are planted, and thick 
woods spring up on the prairies as soon as the ravages of 
the fires are checked.” 
Striking examples of how some of our birds have accept- 
ed this tacit invitation to make men their confidants occur 
