An evaluation of the minimum habitat quality standards for birds in old-growth ponderosa pine forests, northern Arizona

摘要

I studied breeding birds and vegetation in 6 largely pristine old-growth ponderosa pine (Pinus ponderosa) stands and in 3 logged stands that just met the USDA Forest Service's minimum habitat quality standards for old-growth ponderosa pine. Bird populations were similar in all stands. However, brown creepers (Certhia americana) and hermit thrushes (Cattarus guttatus) were low in abundance or absent in 2 of the minimum stands, yet were common in all other stands. Both species preferred cool, moist microenvironments for nesting and/or foraging; conditions that appeared lacking in the more xeric minimum stands. Both species are characteristic of boreal forests, which are cooler and wetter than ponderosa pine forests. I suggest that unlogged old-growth ponderosa pine forests create microhabitats that approximate conditions in more boreal forests. The minimum standards on drier sites appear inadequate in maintaining creeper and thrush habitat. Suggested modifications of the standards include, among others, canopy cover ≥ 50%.