Raptor es of South America. 351 
to an elevation from to about 5000 feet above the level of the sea, 
as far as the 12th degree, an elevation of which we believe the mean 
temperature to be equivalent to that of four or five degrees of lati- 
tude without the tropics, it willjjbe seen, that there must be a de- 
duction from the grand total, of all the species inhabiting this lati- 
tude only in consequence of the extreme height of the Andes. The 
number will thus be limited to twenty-eight, an amount which still 
approaches to two-thirds of all the species observed. At the same 
time the species differing, and peculiar to the second and third zones 
of elevation, give a minimum number of only ten, without including 
such as likewise inhabit a less elevated zone. 
The second zone of latitude (from the 28th to 34th degree) by no 
means presents so many species as the first ; but the diminution is 
gradual, consisting either of the half, if we include all the species 
found at every height of the latitudinal zone, or of a third only, if 
we limit the comparison to those of the zone properly so called ; for 
we then find nineteen species, nine of which belong to the plains, 
and ten to the mountains. Here, therefore, it appears that the num- 
ber of species is as great, or at least equal, on the mountains ; while 
in the first zone of latitude, the birds of the plains were most nume- 
rous. Among these species, four only are proper to the plains, the 
rest being either alpine or of the third zone. 
The third -zone of latitude, (from the 34th to the 45th degree) 
comprehends the smallest number of species, for we have not found 
in it more than seventeen, all of them in the plains or slightly ele- 
vated tracks which stretch from the shores of the sea to the foot of 
the Cordilleras of Chili. The proportion is less than a third com- 
pared with the total amount of species in the first zone of latitude, 
and nearly a half viewed in reference to the number of species of 
the same zone of which we speak. Among the latter, eight are 
likewise found on the summits of the Andes, and nine are Patago- 
nian, or frequent either the dry plains or sea shores of the zone. 
Let us now consider the distribution of the birds of prey relatively 
to the height of their abodes, comparing at the same time the spe- 
cies of the zones of elevation with the species of the zones of lati- 
tude in regard to the most southern. 
Thejirst zone of elevation (from to 5,000 French feet above 
the level of the sea) includes the species which, from the 27 of" 
latitude for example, live always in the plains, but the difference 
of temperature is so inconsiderable, that all the species, at least 
such as are not confined to districts of a particular kind, occupy 
indifferently the lowest and the most elevated situations. 
In the second zone of elevation (from 5,000 to 11,000 feet above 
