218 THE PHILOSOPHY OF BIRDS' NESTS. 
the materials of a nest? Consequently, they all lay 
in holes of trees, the tops of rotten stumps, or in 
deserted ants’ nests, the soft materials of which they 
can easily hollow out. 
Many terns and sandpipers lay their eggs on the 
bare sand of the sea-shore, and no doubt the Duke of 
Argyll is correct when he says, that the cause of 
this habit is not that they are unable to form a nest, 
but that, in such situations, any nest would be con- 
spicuous and lead to the discovery of the eggs. The 
choice of place is, however, evidently determined by 
the habits of the birds, who, in their daily search 
for food, are continually roaming over extensive tide- _ 
washed flats. Gulls vary considerably in their mode of 
nesting, but it is always in accordance with their struc- 
ture and habits. The situation is either on a bare rock 
or on ledges of sea-cliffs, in marshes or on weedy shores. 
The materials are sea-weed, tufts of grass or rushes, 
or the débris of the shore, heaped together with as 
little order and constructive art as might be expected 
from the webbed feet and clumsy bill of these birds, 
the latter better adapted for seizing fish than for 
forming a delicate nest. The long-legged, broad-billed 
flamingo, who is continually stalking over muddy flats 
in search of food, heaps up the mud into a conical 
stool, on the top of which it lays its eggs. The bird 
can thus sit upon them conveniently, and they are 
kept dry, out of reach of the tides. 
Now I believe that throughout the whole class of 
birds the same general principles will be found to hold 
