Bird species diversity and composition in managed and unmanaged tracts of northern hardwoods in New Hampshire

Conservation of biological diversity has become a priority in the natural resource management planning process, yet information on the effects of management practices beyond the scale of single stands is lacking. The objective of this study was to determine whether timber management was compatible with the goal of maintaining forest bird species diversity in the northern hardwoods forest type. Twelve 64-ha study areas, 6 managed for quality sawlogs and 6 not managed for timber, were selected in the White Mountain National Forest, New Hampshire. Managed areas included approximately 60% sawtimber, 20% pole, and 20% sapling even-aged northern hardword stands while unmanaged areas were 100% sawtimber stands $\u3e$80 years old. Young stands were $\u3c$20 ha in size; older stands ranged from about 10 to 140 ha. Bird species abundances were determined in each area from 8-minute counts in June 1989-90 at 16 points spaced 200 m apart. Bird species diversity, as measured by Shannon-Weaver, Simpson, log series alpha, and species richness indices, was greater (P $\u3c$ 0.005) on managed areas than on unmanaged areas. Managed areas included a total of 53 species compared to 33 on unmanaged areas. All 33 species present on unmanaged areas were also present on managed areas. Of 19 species with mean abundances $\u3e$1 individual/area and coefficients of variation $\u3c$50%, the ovenbird was the only species more abundant (P $\u3c$ 0.10) on unmanaged areas, yet ovenbirds were the third most abundant species on managed areas. American redstart, rose-breasted grosbeak, and veery were all more abundant (P $\u3c$ 0.05) on managed areas. The above results suggest small scale timber harvesting can increase forest bird species diversity without loss of any species. These results apply to extensively forested areas of northern hardwoods in the northeastern United States and may not apply in other areas or in areas where harvesting practices are more intensive. Analysis of minute-by-minute bird counts and evaluation of bird surveys for unmanaged areas suggested point counts should be 8-minutes in duration at points $\ge$400 m apart. Travel time between points had a greater effect on efficiency (individuals detected/hour) than count duration. Each point should be surveyed $\ge$3 times, and for a uniform habitat such as mature northern hardwood forest, a minimum of 24 points should be established