354 Observations on the 
their characteristic vivacity. This, indeed, is easily accounted for 
from their mode of life, for they are obliged, more frequently than 
others, to perch at the margin of waters or on the outskirts of woods, 
in order to watch the egress of a frog, a lizard, or an insect, which 
they immediately seize and devour on the ground. They are there- 
fore seldom seen hovering after the manner of our ' e Jean le Blanc,"* 
or our eagles ; for even the Aguia Eagle and the Buzzards, which 
hover most, are observed to do so only for a short time in the day, 
especially in the morning. 
We have noticed among many kinds of American birds of prey 
a sociable instinct wholly unknown to those of Europe, which, with 
the exception of vultures, never unite in flocks. The vultures of 
America are as sociable as those of Europe. They assemble in order 
to devour dead bodies ; and the caracaras, their faithful imitators, 
congregate like them on the same carcases, with a like degree of 
familiarity and confidence ; but in these associations the caracaras 
are probably more influenced by the desire of obtaining a kind of 
food common to both, than by any really sociable feelings. The 
case is different from those assemblies of birds of the same species 
belonging to other tribes, which move from one place to another in 
flocks, alight together on the margin of the same lake, perch on the 
same tree, or even the same bush, in the vicinity of waters and in 
wooded plains, and rarely separate, at least during their movements 
over the country ; for we are yet ignorant whether they congregate 
for an annual migration. However this may be, the birds posses- 
sing this property are the Cymindis with hooked bills (genus Ros- 
tramus, Less.) which in this manner continue in company at least for 
three months in the year, as we assured ourselves by actual obser- 
vation on the frontier of Paraguay. 
The leaden coloured Buzzard (Falco plumbeus, Lath.) has the 
same habits. We have seen them in the skirts of woods resting in 
large flocks on the same dead tree for a whole day together, some of 
them pursuing birds and others reposing, the latter taking wing 
when their companions returned to their perch. It is surprising to 
meet with this social instinct among birds whose mode of life seems 
calculated to render them jealous, quarrelsome, and solitary : and, 
indeed, with the exceptions just mentioned, rapacious birds always 
live alone without experiencing any of that attraction which brings 
animals into companionship with others of their kind. Even in the 
season of love, these voracious birds scarcely remain together in pairs 
for more than two months, when they again separate and take no 
further notice of each other. It is true that, during this interval, 
* F. brachydactylus, Wolf. 
