The Food of Birds 147 
masses of animate gelatine. But the fresh-water hydra, 
belonging to the same division as the hydroids, is eaten 
in myriads by ducks and geese. These and many other 
birds are remarkably fond of duckweed, which they 
devour with such evident pleasure that they must enjoy 
jit as much as cats do catnip, or canaries hempseed. As 
the under surface of these small water plants is the fa- 
Fia. 113.—Butterfly with wing torn by bird. 
vourite home of the hydra, they necessarily form a por- 
tion of the food of these water birds. 
Roundworms, flatworms, and leeches are devoured 
by many aquatic birds, while earthworms form a staple 
article of diet with such different species as thrushes, 
woodcocks, and cranes. A favourite morsel of the curi- 
ous apteryx of New Zealand is a gigantic species of worm, 
twelve to twenty inches in length, which is highly phospho- 
rescent. The apteryx seeks its food by night, and when 
