BIRDS AT WORK AND PLAY. 87 
Some birds, as the swallows, make mud houses, after 
9 v) 
the manner of the Mexicans. We often wonder if 
these people got their idea of house building from the 
birds. 
BARN SWALLOW. 
Other birds use sticks and cement, as a man does 
brick and mortar. Some of the sea birds lay their eggs 
on a bare, flat rock. Even these do not roll off from 
the rock, for all eggs are oblong and cannot roll in a 
straight line. We have never seen a perfectly round 
ego. If you take an egg of any kind, as a hen’s egg, 
and try to roll it down the floor or lawn, you will see 
