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Bird population and community studies at HBEF
Black-throated Blue Warbler female on nest
Black-throated Blue Warbler female on nest

Principal Investigators:
Richard T. Holmes, Dartmouth College (richard.t.holmes@dartmouth.edu)
Nicholas L. Rodenhouse, Wellesley College (nrodenho@firstclass.wellesley.edu)
T. Scott Sillett, Smithsonian Institution (silletts@nzp.si.edu)

Collaborators:
Thomas W. Sherry, Tulane University (tsherry@mailhost.tcs.tulane.edu)
Michael S. Webster, Washington State University (mwebster@wsu.edu)

Date Prepared: March 2003

Introduction and Overview

Bird populations have been studied at the HBEF and surrounding sections of the White Mountain National Forest since 1969. The research focus has examined a variety of topics, ranging from the role of birds in ecosystem nutrient cycling and energy flow (Holmes & Sturges 1973, 1975, Sturges et al. 1974, Gosz et al. 1978), to bird-insect interactions (Holmes & Schultz 1978), bird foraging behavior in relation to insect availability (Holmes et al. 1978, Holmes & Robinson 1981, Robinson & Holmes 1982, 1984), bird community structure (Sabo & Holmes 1983, Holmes et al. 1979, Sherry & Holmes 1985, Holmes et al. 1986), bird reproductive success, survival, nest predation, etc. (Holmes et al. 1992, 1996, Rodenhouse & Holmes 1992, Sloan et al. 1998, Sillett et al. 2000, Sillett & Holmes 2002), and bird population regulation (Rodenhouse et al. 1997, 1999, in review, McPeek et al. 2001, Sillett & Holmes, in press). Additional studies have been conducted on the ecology of some of the same migratory species in their Neotropical wintering areas (Holmes et al. 1989, Holmes & Sherry 1992, Marra et al. 1993, 1998, Marra and Holmes 2001).

As background for all of these ecological and behavioral studies, we have quantified bird abundances on 10-ha study plots near watershed 6 at HBEF from 1969-present and on three replicate plots in nearby parts of the White Mountain National Forest from 1986-2001. These data provide information on long-term population trends of birds occupying these largely undisturbed northern hardwoods forests (Holmes & Sherry 2001, see Fig. 1). Data are archived in Datasets.

Graph of long term patterns in bird abundance

Figure 1. Long term patterns in bird abundance at Hubbard Brook (1969-2000) and on three replicate sites in the White Mountain National Forest

These long-term data show a marked decrease in the total number of birds occupying the study sites. On the main Hubbard Brook study area, total numbers of birds (all species combined) have declined from 210-220 individuals/10 ha in the early 1970s to 70-90/10 ha in the 1990s and early 2000s (Fig. 1, Holmes & Sherry 2001). Of the 24 regularly occurring species, 12 have shown significant population declines, three have increased significantly, and nine have remained relatively constant in abundance. Generally similar population levels and patterns of population change have been recorded on the replicate sites. Probable causes of these trends are diverse and differ among species. Most can be accounted for by individual species’ responses to events occurring primarily in the local breeding area, especially responses to temporal changes in forest vegetation structure and annual changes in food (insect) availability (Holmes & Sherry 2001).

These changes in bird abundances over the study period have led us to focus our current research on the factors and processes that limit and regulate populations of migratory birds. Such information is not available for any migratory species, and is essential for conservation and management of migratory bird populations. Selected aspects of our current research are described at the links below. The broad focus is on population regulation and limitation of migratory bird populations, but include more specific research programs on bird distributions, nesting ecology, behavioral ecology and mating systems, ecology of nest predators, and other topics.

Literature Cited
see list of Publications of the Hubbard Brook Ecosystem Study


Current research in avian ecology at HBEF

Other recent and on-going projects