How Man Affects Birds
Can man and bird live side by side? If not, how far apart should they be. Are some friendlier than others? According to a study by the Wildlife Conservation Society (WCS), impacts to bird communities from a single rural, exurban residence can extend up to 200 meters into the surrounding forest. The study also determined that sensitive bird species such as the hermit thrush and scarlet tanager prefer unbroken forests with no houses. Others, like the blue jay and black-capped chickadee, seem to like having, and often thrive with, human neighbors.
As part of the study, scientists sampled the presence of 20 species of birds both near and far from 30 rural residences in the Adirondack Park. Calculating their occurrence at increasing distances from the residences, they determined that human-adapted species are 36 percent more likely to occur near the homes than in the surrounding mixed hardwood-conifer forests, and that human-sensitive species were 26 percent less likely. Beyond 200 meters, occupancy rates were similar to the surrounding forest.
The Blue Jay is one of the commonly known human friendlies and is is resident through most of eastern and central United States and southern Canada. It breeds in both deciduous and coniferous forests, and is common near and in residential areas. It is predominately blue with a white chest and underparts, and a blue crest.
The Adirondack Mountains are contained within the 6.1 million acres of the Adirondack Park, which includes a constitutionally protected Forest Preserve of approximately 2,300,000 acres. About 43% of the land is owned by the state, with 57% private in holdings, heavily regulated by the Adirondack Park Agency. The Adirondack Park contains thousands of streams, brooks and lakes, most famously Lake Placid.
The report appears in the current online edition of the Journal of Landscape and Urban Planning. Authors of the study are Drs. Michale Glennon and Heidi Kretser of the Wildlife Conservation Society.
Rural exurban development is residential development existing outside of cities and towns, and is generally characterized by larger lot sizes (5-40 acres or more) and lower density than suburban development. Exurban residences exist within an otherwise unaltered ecosystem.
Exurban homes change the environment by bringing vehicles, noise, lights, pets, people, and food sources into the forest, as well as by physically altering and fragmenting habitat. These changes can have myriad impacts, including altered species behavior and composition, increased human wildlife conflicts, new predator-prey dynamics, and decreased biotic integrity.
Biological integrity is associated with how pristine an environment is and its function relative to the potential or original state of an ecosystem before human alterations were imposed. the accepted definition is "the capability of supporting and maintaining a balanced, integrated, adaptive community of organisms having a species composition, diversity, and functional organization comparable to that of the natural habitat of the region." The implications of this definition are that living systems have a variety of scales relative to which they exist, that one can quantify the parts that sustain or contribute to a system's functioning and that all systems must be seen in the context of their environments and evolutionary history.
"Adirondackers take great pride in their surroundings and try not to unduly disturb the natural setting in which they live," said WCS Adirondack Program Science Director Michale Glennon. "A key finding of the study is that the ecological footprint of development can be much larger than its physical footprint. We found that even a small home and lawn can change bird communities some 200 meters away, which means more than 30 acres of the surrounding landscape, depending on what types of activities are occurring on the residential property. It is important that we learn how birds and other wildlife react to particular kinds of human activities, and find ways to minimize the negative impacts for wildlife in exurban areas."
The study found that species sensitive to human impacts include the black-throated blue warbler, black-throated green warbler, hairy woodpecker, hermit thrush, ovenbird, scarlet tanager and the winter wren. The presence of some species, like the scarlet tanager (adult males are bright red with black wings and tail while females are yellowish on the underparts and olive on top) are a good indicator of undisturbed forest health.
The study was modeled after one conducted in a shrub-oak ecosystem in Colorado where scientists calculated a 180-meter ecological effect zone based on their results. Glennon and Kretser believe that the similar results in two different ecosystem types may indicate that human behaviors associated with exurban homes play a larger role in shaping avian community characteristics nearby than do habitat alterations created by construction and clearing.
While breeding bird communities were used to measure the impacts of exurban development in the study, the authors note that birds can serve as valuable indicators of overall biodiversity.
For further information see Birds and Man.
Blue Jay image via Wikipedia.