Effects of habitat fragmentation shrub-steppe birds in Southeastern Idaho. (Biology Paper Abstracts).
Catherine W. Rideout*
Our study examines potential effects of habitat fragmentation on shrub-steppe birds in southeastern Idaho. Nest depredation and brood parasitism are known to increase in habitat fragments, which decrease productivity of birds. Our objective is to determine if and how these processes operate in shrub steppe ecosystems in Idaho by monitoring nesting success of shrub-steppe obligate species (Brewer's Sparrows, Spizella breweri, Sage Sparrows, Amphispiza belli, and Sage Thrashers, Oreoscoptes montanus). During 1999, we established study plots in fragmented and continuous habitats, within which we censused birds and monitored nests. We also conducted experiments using artificial nests to determine potential effects of paved highways, two-track roads, and grassland edges (the predominant fragmenting forces) on nest depredation rates. The three sagebrush obligate passerine species comprised 68.8% of birds counted, but their abundance did not differ between fragmented and continuous habitats. Nor did nest density and nest success rates differ between treatments. However, 90% of brood parasitism by Brown-headed Cowbirds (Molothrus ater) was in fragmented habitat. Experiments using artificial nests suggest that nest depredation is greater near shrub/grassland boundaries (69.6%) and lower near paved highways (50.0%), although depredation rates were high in all experiments.
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|Author:||Rideout, Catherine W.; Belthoff, James R.|
|Publication:||Journal of the Idaho Academy of Science|
|Article Type:||Brief Article|
|Date:||Jun 1, 2001|
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