WINTER FOOD OF THE PARTRIDGE.—SOMERS. 79 
contain little nutritive matter, they are yet always succulent and 
tender, and supply them with the only green food which they can 
procure during our subarctic winter.. The kalmia leaves, you 
will observe, are sear and coriaceous, just as we find them persist- 
ing on the plant during autumn and winter. 
The birch catkins contain the male flowers of this tree locked 
up in their winter sleep. They yield, on analysis, both carbona- 
ceous and nitrogenous matter, and supply, though in limited 
quantity, matters requisite to the nutritive demands of the 
tissues of our Partridge: but, as they contain, also, a large quan- 
tity of insoluble and unassimilable matter, their digestion requires 
to be slowed, so that the soluble and assimilable matter may be 
separated and prepared for absorption into the blood. The firm 
fronds contain a small quantity of starch and mannite, with a 
percentage of nitrogenized matter; they are probably of most 
service supplying to the tissues certain inorganic proximate 
principles which are necessary to their well-being. Salts of 
soda, potassia and lime abound in ferns. These substances are as 
much food requisites as those of organic origin. 
In birds the nutritive processes and circulation are more rapid 
than in mammals, their great muscular activity induces rapid 
tissue change ; they, therefore, require a large amount of food. 
Hence birds are constant feeders. In them, too, the digestive 
process is quick in action, and a diminution in their food supply 
is severely felt and soon shows its effects——they emaciate, lose 
their activity, and become slow and torpid. 
It is well known that birds, considering the size and weight of 
their brains, are uncommonly intelligent. This applies particu- 
larly to the class of birds under consideration, which become 
proverbially shy and cautious in localities where they are much 
sought for by sportsmen; in seasons when food is scarce they 
very often, owing to their diminished activity, become an easy 
prey to the gun. 
In endeavoring to account for the eating of the kalmia leaves 
by the Partridge, and the innocuousness of this plant to the bird 
itself, we may premise that it is taken, not for its nutritive 
value, but because it acts indirectly by preventing tissue change.. 
