1917.] Chapman, Distribution of Bird-life in Colombia. 161 



arid divisions. The first is characterized by a dense low forest of thickly 

 branched, sturdy trees on which grow numerous epiphytes and parasites, 

 including a great variety of mosses. Allen's description of the Laguneta 

 region (Expedition No. 3) gives an excellent idea of Temperate Zone forest. 



The arid portions of this zone include bush-grown or treeless slopes, and 

 the Savanna of Bogota, with its exceptionally favorable haunts for plains- 

 and marsh-loving species. 



The bird-life of the Temperate Zone is composed of an exceedingly 

 interesting combination of species obviously derived from lower zone forms 

 of the same latitude and from forms inhabiting the same zone at a different 

 latitude. 



Thus, Zenaida ruficauda ruficauda, Z. r. antioquice, Troglodytes musculus 

 columboe, and Agelaius icterocephalus bogotensis are racial, intergrading 

 representatives of Tropical forms of the same latitude. While, though 

 now specifically distinct, Penelope montagni, Trogonurus assimilis, Andigena 

 hypoglaucus appear respectively to be zonal representatives of P. cristata, 

 T. -personatus, and A. nigrirostris, all of which are found in the adjoining 

 lower zone. 



Of the second group, or true Temperate Zone species which have ex- 

 tended their range to the higher parts of the Andes from a latitude where 

 this range reaches sea-level, Porphyriops melanops bogotensis is but a slightly 

 differentiated form of P. m. melanops of Paraguay, Scytalopiis niger is found 

 unchanged at sea-level in Chile, and Catamenia analis schistaceifrons is an 

 intergrading form of C. analis analoides which is foxmd on the coast of Peru. 



One of the most interesting results of our study of zonal life is the dis- 

 covery that two forms of Streptoprocne zonaris inhabit the Andes; one, S. z. 

 albidnda, occurring in the Tropical and Subtropical Zones; the other, iS. z. 

 altissima, in the Temperate Zone. Although these closely related forms, 

 when feeding, are doubtless associated, we have found no intergrades be- 

 tween them. The latter indeed, more closely resembles S. z. zonaris of 

 southern Brazil than it does S. z. albicincta, and it is not improbable that it 

 has been derived from zonaris through extension of range with increasing 

 altitude in the Andes, rather than from albicincta. The latter, however, is 

 also a racial representative of zonaris. Hence apparently two forms ha\'ing 

 a common ancestor with which both intergrade, meet as species. 



We must look not only to more southern, but to more northern latitudes 

 if we would discover the ancestral type from which certain species of the 

 Temperate Zone in Colombia were derived. Possibly no more convincing 

 proof of the northern origin of a Colombian Temperate Zone race could be 

 asked for than is furnished by Otocoris alpestris peregrina, a common species 

 of the Bogota Savanna, to which it appears to be restricted. 



