Tuesday, October 05, 2010

Birds and Drought: Winter Birds

In a grassland-oak savannah in southeastern Arizona, Carl and Jane Bock found that ground-foraging, seed-eating birds were 3 times more abundant one year after a 2-year drought ended than in the previous winter. Details from their abstract:
As a group, 19 species of ground-foraging, seed-eating birds (e.g., doves, quail, sparrows, towhees) were 2.7 times more abundant on the exclosure than on adjacent grazed grasslands during the first winter. These same species were 1.7 times more abundant on the exclosure during the second winter and were 2.9 times more abundant on both sites combined after the drought had ended. A second group of 24 avian species with different foraging ecologies (e.g., predators, frugivores, arboreal insectivores) did not differ between treatments or years. High-density, short-duration rotational grazing, coupled with a drought, left the land in a substantially denuded condition through two winters and negatively affected a variety of resident and migratory birds dependent on ground cover and seed production for over-winter survival.

Bock, Carl E., and Jane H. Bock. 1999. Response of winter birds to drought and short-duration grazing in southeastern Arizona. Conservation Biology 13: 1117-1123. URL: http://onlinelibrary.wiley.com/doi/10.1046/j.1523-1739.1999.98313.x/abstract [Abstract only]

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