30 BULLETIN 117, UNITED STATES NATIONAL MUSEUM. 



SUBTROPICAL ZONE. 



The remarkable stratum of life which lies approximately between 

 the elevations of 5,000 and 9,000 feet on the eastern slope of the 

 Andes and extends from Bolivia to Venezuela makes a fold or loop 

 up the Urubamba Valley. In the lower valley its inferior limits 

 merge with the upper border of the humid Tropical Zone in one un- 

 broken sweep of forest; at Santa Ana they are coextensive with the 

 cloud belt below which grassy, treeless slopes reach to the floor of 

 the tropical valley, while from a short distance above San Miguel 

 Bridge (altitude 6,000 feet), at the foot of Machu Picchu, almost to 

 Torontoy, the forests of the Subtropical Zone reach the shores of the 

 river, v/hence, in places, they e?vtend upward to merge with those of 

 the humid Temperate Zone. 



Above Santa Ana the Subtropical Zone is first encountered on the 

 \vestern side of the valley at Idma, and from this point forest extends 

 into the Temperate Zone. 



Birds have been collected in the Subtropical Zone of the Urubamba 

 Valley only at Idma and in the Machu Picchu district. From these 

 localities 105 species have been secured which may be considered as 

 zonaUy representative. Comparison of the results of our work with 

 those of Kalinowski's indicates that this number fairly represents the 

 fauna. It does not, however, fairly represent the fauna of the Sub- 

 tropical Zone of Peru, since in Colombia we obtained 230 species 

 which were distinctively subtropical. The data at hand, therefore, 

 do not warrant a comparison of the bird life of the Subtropical Zone 

 in Peru and ColomJoia, but they do show the remarkable uniformity 

 of the life of that zone, a fact to which I have previously called 

 attention.^^ Thus, of 77 genera secured by us in the Subtropical 

 Zone of the Urubamba Valley, no less than 74 also occur in this zone 

 in Colombia; the genera Kniyolegus, PhyUoscartes, and TMyj>opsis 

 being the only ones absent from Colombia. Of the 104 Urubamba 

 species contained in these genera, 57 are common both to Peru and 

 Colombia. 



TEMPERATE ZONE. 



The Temperate Zone has both a humid and an arid section. The 

 former is found on the more easterly ranges of the Andes, on which 

 are condensed the moisture-bearing winds from the Atlantic. Here 

 well-developed forest reaches an average altitude of 12,500 feet. 

 Above this altitude lies the Puna. The line between the two may 

 be abrupt or the two may merge by an upward extension of bushy- 

 grown areas, the latter forming the arid portion of the Temperate 

 Zone. Heller writes that the forest at Cedrobamba (altitude 12.500 

 feet) ''stops as abruptly as if cut by a knife" and is succeeded by the 

 grassland of the Puna. 



» Bull. Amor. Mus. Nat. Hist., vol. 3G, 1917, p. 135. 



