Realm: Terrestrial
Climate: Temperate
Biome: Temperate broadleaf and mixed forests
Central latitude: 43.910000
Central longitude: -71.750000
Duration: 45 years, from 1970 to 2015

959 records

52 distinct species

Across the time series Piranga olivacea is the most frequently occurring species

Methods

This study was conducted in the Hubbard Brook Experimental Forest. a 3076-ha sector of the White Mountain National Forest. West Thornton. Grafton County. New Hampshire. USA. Our study took place on the 10-ha forest plot de- scribed by Holmes and Sturges (1975). which is located on a relatively steep (20-25%). south-southeast facing slope at an elevation of 500 to 600 m and adjacent to the lower third of watershed 6. the reference area for many of the Hubbard Brook ecosystem studies. The study plot was situated within a large tract of unfrag- mented and relatively homogeneous northern hard- woods forest. > 5 km distant from. and at an elevation 300 m above. the nearest human settlement. The only human-caused disturbances near the study area were on three experimental watersheds. 13. 10. and 22 ha in extent. which were logged by clear-cutting in 1967. in 1970. and from 1973 to 1975. respectively. The nearest of these was 0.6 km from the edge of our plot. the others were 1 and 2 km away. Although some for- est-dwelling birds moved to these areas in mid and late summer to feed on ripening fruit. we have no evidence that birds settling and breeding on the study area were in any way affected by these logged areas.Bird populations Bird censuses were conducted in a consistent manner in each of the 16 summers. These census methods have been described in detail by Holmes and Sturges (1975). Briefly. they involved: (1) Timed censuses. Two ob- servers moved at a rate of 50 m/6 min along parallel transect lines. 1 00 m apart. and recorded all birds heard or seen within 50 m on either side of the line. Since the 10-ha plot was 500 m long and 200 m wide and these lines ran 50 m in from the long sides. the entire plot was surveyed in a 1-h census. From these records. the numbers of individuals observed on the plot were then tallied. A minimum of two such censuses was conducted each week from late May through mid-July. (2) Territory-mapping. The positions of individual males (and females when seen). especially those en- gaged in simultaneous singing with neighbors. were plotted on a gridded census map. From these records. the territories of the males of many species could be delineated. (3) Mist-net captures. Forty to 50 mist nets. located at 50-m intervals on the census grid. were op- erated for 6-8 h/d. usually 1 or 2 d/wk from late May through early July in all years except 1980. Each cap- tured bird was given an aluminum band plus a unique combination of colored plastic bands. Capture and re- capture frequencies provided additional information on the presence of birds on the plot. including females and occasionally floaters. (4) Detailed observations. These provided information on nesting events and on the occurrence of females associated with males. Data from all methods were pooled and used to es- timate the total numbers of adult birds of each species living on the 1 0-ha study area during the breeding pe- riod. late May to early July. Final density estimates were adjusted for territories occurring only partly on the plot (i.e.. if a territory of a mated pair was half off the study area. only 0.5 male and 0.5 female for a total of one bird was counted) and for unmated males. The data therefore represent the total numbers of adult in- dividuals occupying 10 ha of northern hardwoods. For comparisons with most other studies. the numbers of individuals estimated to be on our plot should be di- vided in half to approximate the numbers of breeding pairs. These methods were most efficient for estimating the numbers of relatively small. mostly passerine birds that inhabit these forests. but also most woodpeckers and the one hummingbird species (see Table 2). We were unable to census adequately the raptors (Red-tailed Hawk. Buteo jamaicensis; Broad-winged Hawk. B. platypterus; Sharp-shinned Hawk. Accipiterstriatus; and Barred Owl. Strix varia). Ruffed Grouse (Bonasa um- bellus). Chimney Swift (Chaetura pelagica). and Pi- leated Woodpecker (Dryocopus pileatus). which were present in this forest but ranged over an area much larger than our 10-ha plot. These low-density species are not included in our analyses. Insect Sampling We used two methods to estimate the abundance of larval Lepidoptera (caterpillars). First. during periods of relatively high caterpillar densities (specifically sum- mers 1969 through 1973). we collected their fecal pel- lets (frass) falling from the forest canopy. Following the procedures of Gosz et al. (1973). we placed 20 funnels (each 20 cm in diameter) lined with filter paper and attached to 1 m tall stakes in a rectangular array on the census plot. with adjacent funnels 100 m apart. Frass was collected from the funnels at 2-4 d intervals. dried at 70'C for 48 h. and then weighed. Second. in 10 summers. caterpillars were censused directly on foliage by visually searching at least 80 50- leaf samples (i.e.. 4000 leaves and supporting petioles and twigs) at z2-wk intervals. For this paper. only data from caterpillar counts on beech foliage in the forest understory are presented. because (1) it was cen- sused in more seasons than any other type of foliage. (2) caterpillar abundance there was representative of that occurring on the foliage of other forest trees (R. T. Holmes and J. C. Schultz. personal observation). and analyses of the vertical distribution of caterpillars in this forest showed few if any differences in their abundance among the canopy. subcanopy. and sapling strata (J. C. Schultz and R. T. Holmes. personal ob- servation). Foliage profile measurements For recording changes in the vertical distribution of foliage. we measured the foliage density profile. using the method of MacArthur and Horn (1969). Six sep- arate vertical transects were made along a randomly placed sample line at each of 20 sites located 100 m apart on the study area. The measurements were av- eraged for each site. and then means and standard de- viations of foliage densities at each of seven vertical strata were obtained for the plot as a whole. Data were taken on the plot in 1972-1973 and again in 1982 at the same locations. Student's t tests were used to detect differences in foliage density within each stratum be- tween sampling periods. Unit of abundance = DensityPer10Ha, Unit of biomass = NA

Citation(s)

Holmes, R. T. & Sherry, T. W. (2001) Thirty-year bird population trends in an unfragmented temperate deciduous forest: the importance of habitat change. The Auk, 118, 589–610.
Holmes, R. T. & Sturges, F. W. (1975) Bird community dynamics and energetics in a northern hardwoods ecosystem. Journal of Animal Ecology, 44, 175–200.
Holmes, R. T. & Sherry, T. W. (1988) Assessing population trends of New Hampshire forest birds: Local versus regional patterns. The Auk, 105, 756–768.
Holmes, R. T., Sherry, T. W. & Sturges, F. W. (1986) Bird Community Dynamics in a Temperate Deciduous Forest: Long-Term Trends at Hubbard Brook. Ecological Monographs, 56, 201–220.