Response of Breeding Bird Populations to Habitat Changes in a Giant Sequoia Forest

Thirty species from the montane forest formation com- prised most of the breeding bird population of a giant sequoia forest, with a density ranging from 188 to 311 pairs per 100 acres (40 ha). When some 22 tons of living and dead trees per acre in the brush or sapling layer of this forest were eliminated by cutting, piling and pre- scribed burning, the change in character of vegetation and the openness of the low vegetation zone led to changes in species composition but not in total biomass of the avifauna. This was true because thickets of small trees were the least important vegetation for bird feeding or nesting; the upper canopy and understory were most important, followed by the ground and trunk categories. Two species of ground-feeding and. nest- ing birds and a third ground-nesting species disappeared after treatment. Nesting flycatchers and robins increased in numbers. Compared with results from areas where wildfires or logging operations have made sub- stantial changes in cover type and set succession back severely, this degree of habitat modification resulted in relatively small avifaunal changes.