BIRD LIFP: in the URUBAMBA valley of PERU. 



37 



S5° 9<f es* BO* 75* 70* 65* 60' SS* SO* 45" 40" 5S' 30* 2S* 20' 



Fig. 3.— semi-diageammatic representation of the kange of upucerthia, a genus of the tree- 

 less SOUTH TEMPERATE ZONE, WHICn HAS EXTENDED ITS RANGE FROM PATAGONLV TO COLOMBIA OVER 

 THE TREELESS PUNA OR PARAMO ZONE OF THE ANDES. COMPARE WITH MAP SHQ-WING RANGE OF THE 

 GENUS HeUOCHERA, WHERE THE MARKED ENVIRONMENTAL DIFFERENCES BETWEEN TROPICAL AND 

 TEMPERATE FORESTS, SEPARATED BY BUT FEW MILES, ARE BEUEVED TO HAVE RESULTED IN THE DEVEL- 

 OPMENT OF THE DISIINCT TYPES CHARACTERIZING THE HUMID TEMPERATE ZONE, WHILE SPECIES OP 

 THE PATAGONIAN PLAINS RANGE 4,000 MILES NORTHWARD OVER HIGH ANDEAN PLAINS WITH ONLY 

 SLIGHT DIFFERENTIATION. 



