Reproductive-Cycle and Nesting Success of Mountain White-Crowned Sparrow (Zonotrichia-Leucophrys-Oriantha) in Central Sierra-Nevada
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[edit] Author(s)
- Morton, M. L.
- Osborn, J. M.
- Horstman, J. L.
[edit] Journal
Condor 74.2 (1972): 152-63.
[edit] Abstract
The Mountain White-crowned Sparrow (Zonotrichia leucophrys oriantha) breeds in the high-mountain meadows of the western United States and southwestern Canada and winters in the southwestern United States and northern Mexico ( AOU 1957). Apparently, the Rocky Mountains and the Sierra Nevada provide the greatest amount of habitat suitable for reproduction, but the Cascades and small ranges within the Great Basin also harbor breeding populations (Banks 1964). The habitat elements essential for reproductive success include grass, bare ground, dense shrubs or scrub conifers, water, and on the periphery, tall conifers ( DeWolfe and De- Wolfe 1962). These elements are contained in certain mountain meadows that are often very small and widely separated and which may change in terms of suitability from year to year. This results in a disjunct distribution of breeding birds with as few as one pair at a given locale. Naturally, this has made it difficult to study the breeding biology of these birds and even to describe with accuracy the breeding range. In early June 1968, we looked for 2. 1. oriantha in known breeding areas in the Sierra Nevada and found them in substantial numbers near Tioga Pass, Mono County, California. We then began a 3-year study of their breeding biology. Herein we report on various aspects of the reproductive cycle in this population.
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