%6 THE STORY OF THE BIRDS. 
Some of the fowl forms and others perhaps can de- 
tect, hours afterward, that the human hand has been 
in their nests. Others who hunt solely by sight have 
this sense less developed, and the nostrils are almost 
entirely suppressed in some pelican forms. 
There are some unexplained appearances of the 
voluntary suppression of odor in the game birds 
which are rather well attested. These may be due to 
its dissipation during flight, or the suppression of skin 
secretions during fright, as often happens in any 
animal. 
