14 Annals of the Carnegie Museum. 



Ecological Conditions. 



The ecotogical conditions in the region under discussion are ex- 

 tremely diverse, ranging from arid, cactus-covered wastes to humid 

 tropical forest, and from torrid .lowlands to eternal snows. Since a 

 knowledge of this subject is essential to a proper understanding of the 

 distribution of bird-life in the region we propose to discuss it at some 

 length. 



Caribbean Lowlands. — The general physical and floral aspect of the 

 littoral and lower foothills exhibits a wide variation according to 

 locality. The northeastern portion, where it adjoins the Goajira Pen- 

 insula, is an arid, sandy waste, with very little rainfall. Except im- 

 mediately along the streams the vegetation consists of a variety of 

 cacti and thorny scrub. Of the cacti there are two species in great 

 abundance, the giant cactus and a variety of prickly pear, the former 

 growing to a height of from twenty to thirty feet, with many branches, 

 and with the main trunk often ten to twelve inches in diameter. The 

 thorny scrub consists of several kinds, but practically all the trees and 

 shrubs are furnished with thorns to a greater or less extent. The 

 fringe of vegetation along the streams consists largely of deciduous 

 trees and shrubs, many of which are represented in the " dry forest " 

 of the semi-arid lowlands and foothills contiguous to Santa Marta. 



The section of semi-arid lowlands and foothills extends along the 

 coast from the Cabo de San Juan de Guia to a point near Rio Frio, 

 south of Cienaga, and thus occupies the northwestern part of the gen- 

 eral region. The flora of this part differs but little in species from that 

 of the arid portion just described, but greatly in the relative propor- 

 tions of the various species represented. Cacti are present on the 

 coastal plain, but are much less abundant, and consist largely of the 

 giant cactus, while the more arboreal forms of a thorny nature are 

 preponderant. Along the streams there are the usual deciduous treea, 

 with additions of other non-deciduous kinds which have followed the 

 watercourses down from the hills. On the whole the coastal plain 

 here has relatively less sand and a much greater density of vegetation. 



That part of the coast lying between these two sections is heavily 

 forested, and will be described in detail further on. 



Foothills. — The semi-arid foothills are of two classes, those lying 

 contiguous to the sea and separated from the main mountain mass, 

 and the foothills of the San Lorenzo and Horqueta and of the Sierra 



