1917.] Chapman, Distribution of Bird-life in Colombia. 71 



Zone islands are not infrequent, I know of no pass below 10,000 feet, tlie 

 average height of the range may be said to be about 11,000 feet, and its 

 summit is therefore largely in the Temperate Zone. 



The Eastern Andes also possesses several snow peaks and numerous 

 Paramo Zone islands. So far as we have learned, at only one point, imtil 

 one approaches the northern extremity in Colombia, do they fall below the 

 Temperate Zone, the pass at Andalucia between the upper Magdalena Valley 

 and the Caqueta region having an altitude, as determined by Miller, of only 

 7000 feet. 



In addition to these main branches of the Andean system, all of which ' 

 are connected at their base north of the Ecuadorian boundary, Colombia 

 possesses three other mountainous areas; the Baudo-Panama, what may 

 be called the Amazonian, and the Santa Martan. The Baudo mountains, 

 lying west of the upper Atrato form the true Pacific Coast Range. They 

 are said to attain an altitude of 5500 feet, making their summit subtropical. 

 In discussing the northward extension of the Subtropical Zone into Central 

 America, evidence is presented which is believed to indicate that this range 

 once possessed a greater altitude connecting it with the mountains of the 

 Panama boundary at the north, and Western Andes at the south, at which 

 time it formed a fourth Colombian branch of the Andean system on which 

 the Subtropical Zone was carried into eastern Panama. 



Little is known about the mountains lying east of the Eastern Andes on 

 upper Amazonian drainage (as before remarked), but I can find no evidence 

 of their having an altitude of over 3000 feet, and if this be true, they do not 

 reach above the Tropical Zone. Hamilton Rice "^ writes that the Sierra 

 Chiribiquete "may be a counterfort thrown out from the Suma Paz, and 

 is a chain of crag-like peaks and hog-backs rising to an altitude of over 

 2800 feet." He doubts the existence of the Tunahi or Padavida range, 

 shown by Codazzi. 



The zoological evidence supports the geological belief that the Santa 

 Marta mountains are of independent formation and have had no connection 

 with the Andes. As such, the life of this group above the Tropical Zone, 

 is insular and the study of the geographical origin of its forms is a clearly 

 circumscribed problem, supplemental to that presented by the life of the 

 main Andean chain. 



Aside from these smaller mountain groups, it is obvious that the exten- 

 sion, almost the entire length of Colombia, of three distinct, high mountain 

 ranges, effectively cuts up the Tropical Zone through which they pass into 

 several sections each of which is more or less segregated from the other. 



1 Geog. Journ., 1914, p. 144. 



