352 Observations on the 
the level of the sea) we find nine species, of which two only are 
confined to this region or its localities, the others also belonging to 
the second or third zone of latitude, where they live in plains where 
the temperature is nearly the same, and the surface of the country 
presenting nearly the same aspect as in the elevated zone. Such 
species have found, in the course of their migrations, regions ana- 
logous to those they inhabited in the southern plains. 
The third zone of elevation (comprehending all heights exceeding 
11,000 feet above the sea) presents nine species, among which there 
is only one Alpine bird, the others pertaining to Patagonia and the 
Pampas. 
From the preceding observations it may be inferred that the 
birds of prey always follow the same law of geographical distribu- 
tion as the other series of birds. It is even among them that we 
most frequently find in the third zone of elevation, or in the third 
zone of latitude, which corresponds to it, the reappearance of the 
same species, instead of merely an analogous species, as happens in 
some genera of the following orders. 
The nature of the country must doubtless exercise much in- 
fluence on the place of residence of every species. Such as range 
over the greatest extent of surface offer a proof of this. The con- 
dor, for example, which extends from the most southern countries 
as far as the line, never deviates in its migrations from the vicinity 
of dry and arid mountains ; its appearance in Patagonia is owing to 
the attractions afforded by the high shores of the sea, the neighbour- 
ing mountains of San-Jose, and the analogous nature of the coun- 
tries to those which are its appropriate abode. The same thing may 
be said of the Buteo tricolor, D'Orbig. and the Falco aguia, Temm. 
which belong in particular to mountainous localities. Certain spe- 
cies, however, are exempted from this influence, for the common 
caracara, and the two species of cathartes, inhabit indifferently, 
under all the zones, either plains or mountains, provided there exist, 
where trees are wanting, either bushes or cliffs of rock on which 
they may perch. 
If we examine the distribution of the species in reference only to 
their particular localities, we will see, for example, that very few 
of them inhabit the large forests, and when they do so, it is only 
the outskirts, never the interior, as has been hitherto supposed. 
The districts which most abound in birds of prey, and which they 
love to frequent in preference to others, are those that are either 
slightly elevated, or rather entirely flat, with scattered tufts of 
wood, extensive marshes, and numerous natural waters, the banks 
of which are always wooded. Even the great Harpy, (Harpy ia 
