BURROWING-OWL 4i 
but mostly so during the breeding-season, when 
prey is very abundant, the floor and ground about 
the entrance being often littered with castings, green 
beetle-shells, pellets of hair and bones, feathers of 
birds, hind quarters of frogs in all stages of decay, 
great hairy spiders (Mygale), remains of half-eaten 
snakes, and other unpleasant creatures that they 
subsist on. But all this carrion about the little Owl’s 
disordered house reminds one forcibly of the im- 
portant part the bird plays in the economy of nature. 
The young birds ascend to the entrance of the burrow 
to bask in the sun and receive the food their parents 
bring; when approached they become irritated, 
snapping with their beaks, and retreat reluctantly 
into the hole; and for some weeks after leaving it 
they make it a refuge from danger. Old and young 
birds sometimes live together for four or five months. 
I believe that nine-tenths of the Owls on the pampas 
make their own burrows, but as they occasionally 
take possession of the forsaken holes of mammals to 
breed in, it is probable that they would always 
observe this last habit if suitable holes abounded, 
as on the North American prairies inhabited by the 
marmot. Probably our Burrowing-Owl originally 
acquired the habit of breeding in the ground in the 
open level regions it frequented ; and when this 
habit (favourable as it must have been in such un- 
sheltered situations) had become ineradicable, a want 
of suitable burrows would lead it to clean out such 
old ones as had become choked up with rubbish, 
to deepen such as were too shallow, and ultimately 
