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Abstract
Riparian habitats throughout the Southwest have been altered directly and indirectly by human activities. Many migrant songbird species specific to riparian communities during the breeding season are experiencing population declines. Conversely, the Brown-headed Cowbird (Molothrus ater) benefits from fragmentation of, and livestock grazing in and near riparian habitat. Brood parasitism by cowbirds may accelerate the process of local extirpation of small, remnant populations of migratory songbirds. Cowbird trapping programs have successfully reduced brood parasitism of the Least Bell’s Vireo (Vireo bellii pusillus) and Southwestern Willow Flycatcher (Empidonax traillii extimus) in riparian habitats of California. This removal technique has not been used commonly in riparian habitats of other states but may be beneficial if a significant problem is identified. Preliminary surveys should be conducted to determine abundance and distribution of cowbirds, and nests of potential hosts should be monitored to assess rate of parasitism. It is not likely that remnant populations of migratory songbirds can sustain parasitism rates greater than 30%. We provide trapping, habitat restoration. and research suggestions to improve management strategies for cowbird host nesting in riparian zones.
Parent Publication
Citation
Schweitzer, Sara H.; Finch, Deborah M.; Leslie, David M., Jr. 1996. Reducing impacts of brood parasitism by Brown-headed Cowbirds on riparian-nesting migratory songbirds. In: Shaw, Douglas W.; Finch, Deborah M., tech coords. Desired future conditions for Southwestern riparian ecosystems: Bringing interests and concerns together. 1995 Sept. 18-22, 1995; Albuquerque, NM. General Technical Report RM-GTR-272. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. p. 267-276.
