Raptor es of South America. 



353 



destructor, Sw.) which perhaps more than any other species may 

 be considered a forest bird, always follows the banks of rivers. 



By dividing all these birds into three classes, and considering the 

 number of species which inhabit, first, the wooded lands which we 

 have just described ; secondly, the arid plains merely covered with 

 small bushes ; and finally, the mountains ; the amount of species in 

 the wooded plains will be thirty-three, that is, more than three- 

 fourths of the whole species observed ; in the arid plains it will be 

 nineteen, that is, less than the half of that number, and sixteen, or 

 rather more than a third, for the mountains. It will be understood 

 that these numbers include the species which continually pass from 

 one locality to another. 



From all these observations it follows that the number of species 

 decrease proportionally as we advance from the warm regions to the 

 pole, or as we ascend from the low-lying lands of the tropics to the 

 summit of the Andes : and nearly for the same reason, they like- 

 wise diminish in their passage from wooded tracks to plains, and 

 from plains to mountains. The following little table affords, in a 

 condensed form, a comparative scale of this system of decrease in 

 the number of species. 









ZONES. 









o ^ 



O G 



Op Latitude. 

 ( Scale ofdegrees) 



o a> 

 . '3 



o 0> 



Of Elevation. 



Above the level of the sea 



(to 15° of latitude.) 



O _<U 



^ '3 



O 0) 



5 s- 



Of Habitation. 

 According to the na- 

 ture of the country. 



O.a, 

 • o 

 O V 



3 8- 



1st, 



From 11° to 28° 



28 



From to 5,000 feet. 



2S 



9 

 9 



VVoody places, marsh- 

 es, natural waters. 



33 



2d, 



From 28° to 34° 



19 

 17 



From 5,000 to! 1,000 f. 



Arid& shrubby plains 



19 



3d, 



From 34° to 45° 



Upwards of 1 1 ,000 feet. 



Elevated mountains 



16 



It may be asked why the greatest number of rapacious birds in- 

 habit warm regions, and particularly places in which marshes occur 

 and detached tufts of wood. The reason is, that the majority of 

 South American birds of prey do not feed solely on small birds and 

 quadrupeds, like the greater part of European species, but likewise 

 on land and aquatic reptiles which abound in such situations, as 

 well as on fishes and even insects. In America the falcons are the 

 only Raptores which habitually pursue birds and mammiferas ; all 

 the others eat animals of every description ; a circumstance which 

 made Azara * .suppose that the American birds of prey might share 

 the characteristic indolence of the inhabitants of this quarter of the 

 world. They are in reality much less active than those of Europe, 

 with the exception of the Falconida?, which every where exhibit 

 * Voyages dans I'Amerique Meridhmale, Tom. iii. p. 5. 



