1917.] 



Chapman, Distribution of Bird-life in Colombia. 



147 



Fauna are those of its zone. It cannot be said to have arid sections. When 

 the humidity falls below the point required to produce the forests which 

 Subtropical Zone species require, the zone practically disappears and its 

 place is taken by an upward extension of the Tropical Zone and a downward 

 extension of the Temperate Zone. 



Aside from representative forms of species of general Subtropical distri- 



Fig. 16. Distribution of Formicarius rufipectus. A species of the West Andean Subtropical 

 Fauna which occurs in eastern Panama, western Panama and Costa Rica but is unknown in the inter- 

 vening Tropical Zone. It is represented in the Subtropical Zone of eastern !^cuador by F. thoracicus. 

 1. Formicarius rufipectus rufipectus. 2. F. r. carrikeri. 



bution in Colombia, we have taken thirty-one species peculiar to the West 

 Andean Fauna, but only twenty-two peculiar to the East Andean Fauna. 

 Nevertheless, as we have seen, the West Andean Fauna occupies a compara- 

 tively restricted, isolated area, and at the south, whence it seems evident 

 subtropical life was derived, it is entirely cut off from corresponding areas. 



