File:The American Museum journal (c1900-(1918)) (17973345939).jpg

Title: The American Museum journal
Identifier: americanmuseumjo04amer (find matches)
Year: c1900-(1918) (c190s)
Authors: American Museum of Natural History
Subjects: Natural history
Publisher: New York : American Museum of Natural History
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: Biodiversity Heritage Library

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THE AMERICAN MUSEUM JOURNAL CLIMATIC Vx^RIATION IN COLOR AND SIZE OF SONG SPARROWS. Illustrating Evolution by Environment. I HE first exhibit of several designed to illustrate variation in the color and size of birds due to climatic agencies, has recently been placed in the local bird hall and is here figured. It includes the leading types of Song Sparrows, a species which is particularly susceptible to the influences of its environ- ment, no less than twenty climatic varieties, geographical races, or subspecies of this wide-ranging bird being known. Observe that east of the Rocky Mountains, in a region where climatic conditions are quite uniform, only one well-marked sub- species of Song Sparrow is found; but that west of the Rocky Mountains, where there are widely varying climatic conditions, sixteen subspecies of Song Sparrow are known, twelve of them from California alone. Note the striking relation between the colors of the various races and the aridity and the humidity of the areas they inhabit. Thus the palest-colored race, the Desert Song Sparrow (No. 5, Melospiza cinerea fallax), inhabits the most arid portion of North America, the desert region of Nevada, Arizona and southeastern California, where the annual rainfall averages about six inches; while the darkest-colored race, the Sooty Song Sparrow (No. 2, Melospiza cinerea riifina), inhabits the most humid portion of North America, the coast region of British Columbia and south- ern Alaska, where the annual rainfall may reach one hundred and twenty-five inches. Note that, in obedience to the law that animals increase in size toward the north, the largest race, the Aleutian Song Spar- row (No. I, Melospiza cinerea cinerea), is the most northern, and, the smallest race, the Mexican Song Sparrow (No. 6, Melospiza cinerea mexicana), is the most southern. Between the lightest and darkest, the smallest and largest. Song Sparrows, however, there is comj)letc intergradation in accordance with the change in the conditions which afi^ect their color and size. f. m. c. I 8

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