Abundance and productivity of birds over an elevational gradient

Abstract

This study is investigating the abundance and productivity of birds breeding in four forest types over an elevational gradient in conifer forests of the southern Sierra Nevada of California to identify the most productive habitats for each species, and to examine elevational shifts in abundance, especially as they relate to temperature and precipitation. Species richness and abundance decreased with increasing elevation, although higher elevations were important for cavity-nesting species. Abundance and nest success varied across years and forest types. Dark-eyed juncos (Junco hyemalis) were most abundant at the lowest and highest elevations and had their highest nest success in the lodgepole pine (Pinus contorta) forest type. Excluding the ponderosa pine (Pinus ponderosa) forest type, where they were rare, dusky flycatchers (Empidonax oberholseri) were least abundant in true fir sites but had their highest nest success and productivity there. Abundance vs. nest success and number of young fledged were both negatively correlated, suggesting that dusky flycatchers were unable to assess the probability of successfully nesting in a given habitat prior to settling. In accordance with expectations, 15 species exhibited downslope elevational shifts following severe winters in 1995 and 1998, and six species exhibited upslope shifts.

Parent Publication

• Proceedings of a Symposium on the Kings River Sustainable Forest Ecosystem Project: Progress and Current Status

Citation

Purcell, Kathryn L. 2002. Abundance and productivity of birds over an elevational gradient. In: Verner, Jared, tech. editor. Proceedings of a Symposium on the Kings River Sustainable Forest Ecosystem Project: Progress and Current Status. Gen. Tech. Rep. PSW-GTR-183, Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 121-132