91 
“ Whilst studying the fauna of the Russian steppes, he (Syevertsofif) 
once saw an eagle belonging to an altogether gregarious species (the 
white-tailed eagle, Haliaetos albicilla) rising high in the air ; for half 
an hour it was describing its wide circles in silence, when at once its 
piercing voice was heard. Its cry was soon answered by another 
eagle which approached it, and was followed by a third, a fourth, and 
so on, till nine or ten eagles came together and soon disappeared. In 
the afternoon Syevertsoff went to the place whereto he saw the 
eagles flying. Concealed by one of the undulations of the steppe, he 
approached them, and discovered that they had gathered around the 
corpse of a horse. The old ones, which as a rule begin the meal first 
—such are their rules of propriety—already were sitting upon the hay 
stacks of the neighbourhood, and kept watch, while the younger ones 
were continuing the meal, surrounded by bands of crows. From this 
and like observations Syevertsofif concluded that the white-tailed 
eagles combine for hunting. When they all have risen to a great 
height they are enabled, if they are ten, to survey an area of at least 
twenty-five miles square ; and as soon as any one has discovered 
something he warns the others. Of course it might be argued that a 
simple instinctive cry of the first eagle, or even its movements, would 
have had the same effect of bringing several eagles to the prey, but in 
this case there is strong evidence in favour of mutual warning, 
because the ten eagles came together before descending towards the 
prey, and Syevertsoff had, later on, several opportunities of ascer 
taining that the white-tailed eagles always assemble for devouring 
a corpse, and that some of them—the younger ones first—always keep 
watch while the others are eating. In fact the white-tailed eagle— 
one of the bravest and best hunters—is a gregarious bird altogether, 
and Brehm says that when kept in captivity it very soon contracts an 
attachment to its keepers.”—^Kropotkin, pp. 348-g.) 
Longfellow testifies to similar conduct on the part of 
the vultures. 
“ Never stoops the soaring vulture 
On his quarry in the desert, 
On the sick or wounded bison ; 
But another vulture watching 
From his high aerial look-out, 
Sees the downward plunge, and follows ; 
And a third pursues the second, 
Coming from the invisible ether— 
First a speck and then a vulture, 
Till the air is dark with pinions.”