1917.] Chapman, Distribution of Bird-life in Colombia. 75 



The presence of heavy tropical forest in the southern part of the Mara- 

 caibo basin has been made known to me by W. H. Osgood and Ned Dearborn, 

 both of whom have visited this region in the interests of the Field Museum. 

 As above remarked, I do not know whether this forest is connected with 

 that of the lower Magdalena Valley by a belt of foothill forest, such, for 

 example, as we found above Villavicencio; but at the east it appears to be 

 bordered by the arid coastal region and Venezuelan Andes. It seems, 

 therefore, to be an isolated area; nevertheless, it lies at the door through 

 which many species have entered the Cauca-Magdalena fauna. Its con- 

 nections to the eastward are of much importance, but I have no information 

 Concerning them. 



Of the Santa Marta forest, M. A. Carriker, Jr., our authority on that 

 region, writes me that on the Carribbean or northern side, from about 

 Cabo de San Juan de Guia, to a point known as Camarones, the forest of 

 the Sierra Nevada extends right to the coast. He adds: "Whether there 

 is any forest connection between the Sierra Nevada and the Cerros Negros 

 (Eastern Andes) on the watershed between the Rio Hacha and Rio Cesar, 

 I do not know; most likely there is some such connection, although I am 

 not of the opiuion that it is heavy forest. This watershed is very low." 



The forest west of the Sierra Nevada, Carriker writes, "extends west- 

 ward to the shores of the Cienaga Grande .... The region between Cienaga 

 Grande and the Magdalena is swampy and contains many sluggish water- 

 ways and is inundated frequently. ..." 



Unforested Tropical Areas. — That part of the Tropical Zone in Colombia 

 not covered by heavy forest growth may be grouped under four heads: (1), 

 the Llanos; (2), the Caribbean; (3), the upper Magdalena and (4) the 

 upper Cauca or Cauca Valley proper. Aside from these major divisions 

 there are semi-arid pockets like the upper Dagua on the western slope of 

 the Western Andes, bare foothills such as exist above Dabeiba, or brush- 

 grown valleys like that of the lower Rio Negro, but these and similar local 

 variations do not affect the general truth of our classification. 



The Llanos occupy that part of Colombia lying east of the Andes and 

 north of the Rio Guaviare. Of them Rice {I. c, p. 139) writes : " The Llanos, 

 extending from the Cordillera to the Orinoco river, and from the Arauca 

 to the Guaviare, are covered with dense, tall grasses, from which here and 

 there rise groups of palms and bushes and belts of trees. They are well 

 watered by innumerable streams, varying in volume and size from immense 

 rivers to rivulets, which in winter season overflow the lower lands." 



Of the Llanos of San Martin the same author writes : " To the east they 

 are broken by swales, swamps, and eminences of mesa and scarp formation 

 which push the Humadea river northeast and deflect the Ariari southeast. 

 The high Llanos, at the foot of the forested hills are usually rocky, and semi- 



