SCRATCHING BIRDS. 167 
Fig. 135.—Domestic Pigeons. 
from the arctic regions, discolor and fill the ocean to the 
extent of mighty kingdoms. To talk of hundreds of mil- 
lions of individuals of the same species habitually associ- 
ated in feeding, roosting, and breeding, without any re- 
gard to climate or season as an operating cause in these 
gregarious movements, would at first appear to be whol- 
ly incredible, if not borne out by most abundant testi- 
mony. The approach of the mighty feathered army with 
a loud rushing roar, and a stirring breeze, attended by a 
sudden darkness, might be mistaken for a fearful tornado. 
For several hours together the vast host, extending some 
miles in breadth, still continues to pass in flocks without 
diminution. At the approach of the Hawk their sublime 
and beautiful aerial evolutions are disturbed, like the ruf- 
fling squall extending over the placid ocean.” Audubon 
calculated, estimating one of these flocks to be a mile in 
width, and allowing two pigeons to each square yard, 
that it numbered eleven hundred and fifteen millions, and 
that the quantity of food necessary for its supply must 
