106 Bulletin American Museum of Natural History. [Vol. XXXVI, 



Cacicus vitellinus Leistes nnlitaris 



" hsemorhous affinis Icterus auricapillus 

 " ixropygiaMs pacificus " mesomelas salvini 



Amblyoercus solitarius " hondae 



" holosericeus flavirostris ' " xanthornus xanthornus 



Cassidix oryzivora violea ' Megaquiscalus major assimilis 



Molothrus bonariensis atronitens ^ ■, ^ . , 



„ „ 1. • • Family Corvidce 



" ' cabamsi ■' 



" " asquatorialis Cyanocorax affinis affinis 



Agelaius icterocephalus icterocephalus " violaceus / 



THE FAUNAS OF THE TROPICAL ZONF. 



The Colombian-Pacific Fauna. — Th3 fauna for which I propose this 

 name is one of the most circumscribed and sharply defined, and possibly 

 the most strongly characterized of any fauna of tropical South America. 

 Certainly no other area of similar extent in the Tropical Zone has so many 

 birds which are peculiar to it. 



In brief, this fauna occupies the entire humid Pacific coast region of 

 tropical South America. This includes the whole extent of the Colombian 

 coast and the more northern portions of the coast region of Ecuador. Its 

 southern limits are marked by the northern limit of what may be termed the 

 Equatorial Arid Fauna. 



The boundaries of these faunas remain to be determined. Roughly 

 speaking they may be found in the Province of Manavi, where the Arid 

 Fauna finds its northern limit near Bahia Caraque. The humid Colombian- 

 Pacific here recedes from the coast and extends south of Bahia Caraque in the 

 region of heavier rainfall near the base of the Andes. 



Northward, the Colombian-Pacific Fauna contributes an important 

 element to the composite life of the lower Cauca-Magdalena district, which 

 it enters through the forested region at the end of the Western Andes; north- 

 westward it continues into the Tuyra region of eastern Panama, where it is 

 also associated with Cauca-Magdalena species, which, like Ostinops decu- 

 manus and Donacobius atricaplllus albivitta, are of purely eastern origin. 



Many Central American species appear to have been derived from this 

 small but important area, and its influence may be traced even into southern 

 Mexico; but as a fauna, we may perhaps set its northern boundaries in the 

 Tuyra River system of eastern Panama. 



Climatically, the Colombian-Pacific Fauna is distinguished by an excep- 

 tionally heavy rainfall. Exact meteorological data are lacking, but, as else- 



1 Ranging upward to Subtropical Zone. 



2 Ranging upward to the Temperate Zone. 



