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Ecological Aspects of Bird Distribution in Tropical Africa

James P. Chapin
The American Naturalist
Vol. 57, No. 649 (Mar. - Apr., 1923), pp. 106-125
Stable URL: http://www.jstor.org/stable/2456453
Page Count: 20
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Ecological Aspects of Bird Distribution in Tropical Africa
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Abstract

The general conclusion to be drawn from my map is that although temperature may be a distributional factor of weight, it acts most visibly along certain critical lines, as that, for instance, where occasional frosts first occur. Such a line may be a rough boundary for the tropical life zone, altitudinally as well as on the north and south. Other similar lines are found as the subarctic region is reached, and on mountains, where trees disappear. Within the limits of the tropical zone, temperature alone has no further effect on distribution; humidity now becomes the predominating factor. Its effect upon bird distribution is produced through the development or the paucity of vegetation, the relation between plant associations and their bird inhabitants being particularly close in the African tropics. Avifaunal lines of demarcation are never more sharply defined than the changes in composition and habit of the vegetation. A difference in plant associations may also serve as an isolating factor, just as often as altitude. More than likely, the isolation by altitude, indeed, is again secured through changes of the montane plant-formations.

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