The distribution of birds in Venezuelan páramos. Bulletin of the AMNH ; v. 162, article 2

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New York : American Museum of Natural History
"Páramos are insular in distribution and thus of interest to biogeographers. In the present paper new data are given on geographical distribution, ecological preferences, relative abundance, general behavior, and breeding of 47 species of birds studied on nine Venezuelan páramos in March-April 1975. Some data obtained in March 1968 and in May 1970 are also included. Páramo vegetation is defined as the open formation growing above the upper limit of continuous montane forest in the Andes of Venezuela, Colombia, Ecuador, and northern Perú. This vegetation consists of grasses, herbs, low shrubs, cushion and rosette plants. Polylepis woodlands constitute true islands of a vegetation type distinct from, but growing within, páramo vegetation. A páramo species is a bird inhabiting one of six ecological categories distinguished within the páramo vegetation. The result of six censuses, carried out at altitudes from 3100 m. to 4430 m. suggest that bird species are unevenly distributed altitudinally in Venezuelan páramos. The way birds utilize four major features of the páramo (Espeletia spp., shrubs, water, and barren ground) is discussed. Geographical patchiness in birds of Venezuelan páramos is analyzed in terms of six variables: (1) incomplete sampling; (2) differences in dispersal ability; (3) lack of suitable ecological requirements; (4) exclusion by interspecific competition; (5) historical reasons associated with human modifications of habitats; and (6) historical reasons associated with Pleistocene fluctuations of climate and vegetation. Three major source areas can be postulated for colonization of páramos (North and Central America, adjacent areas of northern South America, and southern South America). Several species may have colonized the páramos of Venezuela from two or three source areas"--P. 51.
p. 49-90 : ill., map ; 26 cm.
Includes bibliographical references (p. 89-90).