Todd-Carriker: Birds of Santa Marta Region, Colombia. 93 



they have entered the region by way of the Venezuelan Andes rather 

 than by the Eastern Andes. 



Such evidence as this points unmistakably towards a former con- 

 nection of the Sierra Nevada with the mountains in northern Ven- 

 ezuela, the general trend of which is similarly parallel with the coast 

 line, but which appear to approximate the northeastern spur of the 

 main Andean system very closely, although the two are not actually 

 joined above the elevation of 4,500 feet at the present time. 17 The in- 

 dications are that these coast mountains are the remnants of an an- 

 cient system which originally was much more extensive, and reached far 

 out into the Caribbean Sea, beyond the chain of islands known as the 

 Leeward Islands (embracing the Dutch West Indies, Los Roques, 

 Orchilla, Blanquilla, etc.). At this period the Sierra Nevada de Santa 

 Marta must have formed the westernmost extension of this great 

 system, which was a prominent feature of the geography of the south- 

 ern continent long before the Andes were elevated above the general 

 level. Possibly the several genetically isolated Sierra Nevadan species 

 may have originated independently at this time, but if so they must 

 have developed with the mountains standing at the same level, instead 

 of as a result of a gradual elevation over a given area, as was prob- 

 ably the case with the Andean forms. This statement is predicated 

 upon the fact that the mountain system in question was in existence 

 prior to the Tertiary, when we believe that evolution of avian forms 

 was at its height. Subsequently to this period, after the Venezuelan 

 Andes were thrown up, a connection with them was established, suf- 

 ficient to carry the fauna of the Subtropical Zone from one to the 

 other. It would seem as if the coast range must have received by far 

 the larger part of its Subtropical forms from this source. Subsequent 

 erosion or subsidence has since destroyed the connection, and subsi- 

 dence on a grand scale, leaving only the tops of the former mountains 

 above the level of the sea in the form of islands, has completely 

 separated the two ends of the once continuous chain, inducing- further 



17 Cf. Sievers, Petermanns Mitteilungen, XLII, 1896, pi. 11. It should be 

 explained that up to this point we have used the term " Venezuelan Andes " 

 to cover both the Andes of Merida and the coast range. There is known to be 

 some difference between the Subtropical Zone faunas of these two ranges, 

 which we hope to discuss in another connection, but this circumstance need 

 not affect the validity of any conclusions we may reach with reference to the 

 Sierra Nevada. 



A 



