In order to study dispersive altitudinal behavior of birds as an adaptation to the mountain, there were conducted biweekly census by the ?Points Method?, between October 2009 and September 2010, in 33 fixed points in ?Serra da Estrela?, Portugal, since 400 to 1993 meters of altitude. The birds community presents a high specific diversity (n=133 species). The resident species present a major representativeness (n=58; 48%), while the remaining are migratory. From the variation of population numbers of resident passerines, it appears that ?time? and ?altitude? presents a significant influence in their relative abundance, evidence of pronounced seasonal altitudinal movements. Of these, 35% perform altitudinal movements (n=14), being possible to distinguish four variation patterns of altitudinal distribution: (1) species distributed mainly by higher areas during reproduction and by the basal areas in winter (n=6 species); (2) species distributed mainly by higher areas during reproduction and uniformly throughout the altitudinal gradient in winter (n=1 species); (3) species distributed uniformly across the altitudinal gradient during reproduction and mainly in the basal areas in winter (n=5 species); (4) species in spite of distributing themselves preferentially by basal areas throughout the hole year, during reproduction they suffer a decrease of the effective in basal floors in detriment of an increase in higher areas (n=2 species). Only 31, 5% of the variation of abundances is related with biophysical factors, while the variables related to habitat and time of the year, present major significance than climatic factors. It is concluded that the altitudinal movements aren?t a direct response to climatic factors but to the changes that they induce in the biotypes. The largest proportion of the variation is justified by biological factors such as availability of resources and competition.

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