Individual study: High nesting failure due to cowbird parasitism in pinyon-juniper woodland within 4 km of grazing
Goguen C.B. & Mathews N.E. (1998) Songbird community composition and nesting success in grazed and ungrazed pinyon-juniper woodlands. Journal of Wildlife Management, 62, 474-484
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Exclude grazers from semi-natural habitats
A study from 1992-5 in New Mexico, USA (Goguen & Mathews 1998), found no significant differences in songbird abundance or species richness between pinyon-juniper woodland sites that were actively grazed and sites from which livestock grazing had been excluded for 20 years (39 species on ungrazed sites, 36 on grazed). However, the authors argue that the slow growing woodland may not have had time to recover over the study period. One species, the western scrub-jay Aphelocoma californica, was more common on ungrazed sites. The authors note that over 75% of blue-gray gnatcatcher Polioptila caerulea, solitary vireo Vireo solitarius and western tanager Piranger ludoviciana nests were parasitised by brown-headed cowbirds Molothrus ater, raising concern that pinyon-juniper woodland habitat close to grazed areas could act as a population sink for songbirds due to cowbird parasitism.