172 
OUR BIRDS IN WINTER. 
bills in the water. Now, these fishes are not 
always to be obtained, and a supply of food 
depends very much upon the elements ; be- 
sides, the sand, as you all know, retains a 
great deal of heat ; the sun, shining down upon 
it, warms it thoroughly, and the eggs laid 
upon it are kept as warm as if their parent 
were sitting upon them. 
But I have not shown why the eggs were 
laid so late, for, if the birds by instinct depend 
upon the sun to hatch them, why not lay them 
in June, for the sun of that month is as warm 
as that of any other part of the season. 
The reason is this, the young of these 
Terns, or Sea Swallows, are fed entirely upon 
small fishes ; young fishes that are hatched and 
grown during the spring and early summer. 
Now if the eggs had been laid, and the 
chicks hatched earlier than their food was 
ready, what would they have to support them ? 
Nothing ; they would starve, just as our young 
ones would, if the caterpillars and worms and 
insects should die all at once. 
It was noticing the Sea Swallows, and 
