138 ON THE INSTINCTS OF BIRDS. 
sideration. But, even supposing this notion to be 
correct, it does not in the least affect the instinctive- 
ness of the act, unless we conclude, with Darwin, 
that instinct has nothing to do with any of those 
actions which result from the repeated efforts of the 
muscles under the conduct of the sensations or de- 
sires—an opinion so manifestly erroneous that it does 
not require a formal refutation. 
The habits and manners of birds are sometimes so 
greatly modified by the exercise of the intellectual 
faculties, that in many cases it becomes extremely 
difficult, if not impossible, to determine what is due 
to their influence ; but that no small portion of intel- 
ligence is exhibited in the following imstances will 
scarcely be denied. 
The White-headed Eagle and several of the Gulls, 
which prey upon the finny inhabitants of the waters, 
frequently save themselves the trouble of fishing by 
robbing their more expert and less powerful congeners 
of the fruits of their industry, occasionally compelling 
the objects of their violence even to disgorge their 
undigested food *. 
* The late John James Audubon, Esq., the celebrated author 
of the splendid work on ‘American Ornithology,’ informed 
me that when the White-headed Eagle pursues the Fish- 
Hawk or Osprey for the purpose of depriving it of its prey, 
it does not, in the first instance, attempt to rise above it, as 
stated by Wilson in his ‘Ornithology of the United States 
of America,’ vol. iv. pp. 90 & 91, but, following it closely, 
urges it from below to as great an elevation as possible, 
