1917.] Chapman, Distribution of Bird-life in Colombia. 153 



levels than we have found them in Colombia, possibly in response to local 

 conditions peculiar to that miniature transcontinental republic. The close 

 relation existing between Colombia and Costa Rican subtropical bird-life 

 is most striking. In many cases, the same species is common to both 

 countries. In others, slightly differentiated races of the same species occur, 

 and in others still, unquestionably representative, but now distinct, non- 

 intergrading species are found. A list is appended of the species which may 

 properly be considered as belonging to these classes. It shows that some 

 sixty-odd species of Colombian subtropical birds are present or represented 

 in Costa Rica, and usually also in western Panama. About twenty-three 

 of these are found on the subtropical crests of the mountains of eastern 

 Panama, but between these localities these species are not known to occur. 

 An orographic map shows that the Subtropical Zone of the northern end of 

 the Western Andes is separated from the subtropical crests of the mountains 

 on the Colombian-Panama boundary by a tropical area of approximately 

 seventy-five miles in width; while the Subtropical Zone of eastern Panama 

 is separated from the same zone in western Panama by not less than three 

 hundred and fifty miles. Doubtless some of the species in the following 

 list will be found in the intervening area. Thus far, however, not one of the 

 species included in the appended table has been recorded from between 

 eastern and western Panama and more than two-thirds of them are unknown 

 from between the northern end of the Western Andes and western Panama. 

 In other words, there is an apparent hiatus in their range of somewhat over 

 four hundred miles. This statement is based not alone on published data, 

 but on the examination of numerous specimens, including those contained 

 in Goldman's fine collection from the Canal Zone and adjoining territory 

 and eastern Panama which, through the courtesy of the Biological Survey, 

 I have been permitted to see. Goldman reached the subtropical Zone on 

 Mt. Pirri and found there most of the subtropical species listed under 

 Eastern Panama in the subjoined table. None of these, however, was 

 taken elsewhere, though in his work in and near the Zone he collected on 

 Cerro Azul at an altitude of 3000 feet. 



Anthony and Ball, of the American Museum Panama Expedition of 

 1915, discovered a number of subtropical species (including the distinct 

 Scytalopus panamensis) on the crest of Mt. Tacarcuna, at an elevation of 

 about 4500 feet. But Richardson's extensive collections from the Tropical 

 Zone of eastern Panama, as might be expected, contained none of the species 

 which characterize the higher, subtropical altitudes. If then thiese sub- 

 tropical species are not found in the tropics immediately below the zones in 

 which they occur, it is of course not to be expected that they will occur in 

 the tropics elsewhere. Consequently, the absence of subtropical altitudes 



