Dummerston Birds are Changing-Hector Galbraith
In the early 1970’s it began to become apparent to ornithologists in Vermont that the State’s birdlife was changing. Changes in land use, such as the reforestation of agricultural land, were leading to major habitat alterations and consequent changes in breeding bird populations. In 1976 work was begun on the Vermont Breeding Bird Atlas, the purpose of which was to map the distribution of breeding bird species, and to provide a baseline against which future distribution changes could be measured. The project, which ran for five field seasons, was spearheaded by the Vermont Institute of Natural Sciences (VINS) and involved the participation of over 200 volunteer fieldworkers. It culminated in 1985 in the publication of The Atlas of Breeding Birds of Vermont, containing distribution maps for over 175 species. It is worth noting that the Vermont atlas project was the first of many subsequently carried out in a number of states – once again, Vermont is ahead of the curve!
The habitat changes that were first noticed in the 1970s have continued apace: the demise of farming in many areas has led to the reforestation of grasslands; urbanization has eaten up rural habitat. Most recently, global change has become important with the advent of global warming. Recognizing these continuing changes, staff of VINS realized that the time was right to repeat the atlas to determine just how bird populations in Vermont were responding. So, beginning in the summer of 2003 field work on the second atlas began.
Given the size of the state and the relatively small numbers of experienced birders it would not be possible to adequately survey all of the state. So, the state was divided up into 179 geographical “blocks”. Each block is 25 square kilometers in area and they were randomly selected from US Geological Survey topographic maps. Each of the blocks were surveyed in the original atlas project and are now being resurveyed for the second atlas.
In Dummerston one block was surveyed in the 1970s and is currently being resurveyed. In addition, a second block was chosen for the current atlas project. What do the results of surveying these blocks tell us about the richness of the Dummerston breeding bird communities, and what changes have occurred between the 1970s and the present? Although the blocks have not been entirely completed, it is now possible to draw some preliminary conclusions:
Dummerston Breeding Bird Communities
Dummerston supports a relatively rich diversity of birds. Totals of 91 and 89 breeding or potentially breeding bird species have been recorded thus far from the two blocks. These high totals are reflections of the diversity of habitats found in the town. Dummerston also supports some breeding species that are relatively uncommon elsewhere in Vermont, Examples include the Carolina wren, the red-bellied woodpecker, and blue-gray gnatcatcher.
Changes Since the 1970s
Since the 1970s a number of bird species have ceased to breed in the original Dummerston block. However, a number of new species have colonized the block. These, which I refer to as “losers” and “gainers”, respectively, are shown below.
Black duck Canada goose
American kestrel Wild turkey
Brown thrasher Turkey vulture
Eastern towhee Red-bellied woodpecker
Eastern meadowlark Least flycatcher
It may come as a surprise to some that birds that we now consider common in the area, such as wild turkey and Canada goose, did not breed here 25 years ago. These species have been introduced and encouraged by state game agencies, explaining their rapid expansion. The colonization by red-bellied woodpecker, Carolina wren, tufted titmouse and turkey vulture are less easy to explain but may be connected with the climatic warming that has occurred over the last three decades. The loss of the kestrel, meadowlark, brown thrasher, and the towhee are all probably connected with the shrinking area of grassland in Vermont, as pasturelands, hayfields, and brushy field borders are being replaced with forest. Why black duck no longer breeds in the area is a puzzle, but this is a species that has suffered a general range contraction in New England so it is likely due to some regional, rather than local, factors.
The current atlas project has two more field seasons to run. After that, it is likely that the results will be compiled in a book. This, together with the results of the 1970s atlas will comprise an important testimony to the changes that are taking place in Vermont bird life in general and in towns like Dummerston.