 |
William
McDonough suggests that "A building should be judged by the number
of birds that can be heard singing outside of the building." The
merit of a building should be assessed according to the health of
natural environment outside, and one way to measure health could be
taking songbird counts. This is an admirable idea, but is it a
realistic way to judge the impact that a building has on its
surrounding environment? How could one transform this idea into a
testable methodology? What are the complexities and limitations?
There is an
opportunity to explore this idea with the new Visitor Education
Center at the North Carolina Botanical Garden. The Botanical Garden
has recently broken ground for the three buildings pending LEED
Platinum certification. Many green building practices are being
implemented, including a geothermal heating and cooling system and
local building materials.
The 10-acre parcel of land that will
host the visitor center was once a farmed area. From approximately
1750 to 1920 it supported crops that may have included cotton and
corn. The forest that was cleared several months ago was 80-100
year-old Shortleaf Pine (Pinus echinata) forest with an
invading hardwood understory. Recently there was a Southern Pine Beetle
infestation that resulted in many dead trees and openings in the
canopy. Surrounding the cleared area is mature mixed hardwood
forest, American Beech-Maple on lower slopes and Oak-Hickory on
upper slopes. Approximately 500 acres of such hardwood forest
extends south of the property where it sits close to Jordan Lake.
 |
When thinking about the environmental impact of a building on birds, it is important to start with an inventory of expected avifauna. We obtained a weekly frequency checklist for all birds recorded in Orange, Durham, and Chatham Counties in 2007 from the Chapel Hill Bird Club (Chapel Hill Bird Club 2007). The list was compiled by Will Cook, a local bird enthusiast who is also a research associate at Duke University. It contained 342 species, which was a bit unwieldy for our purposes, and we started by shortening it to a list of forest songbirds. A songbird has typically been defined as a small bird, usually of the Passerine order, or perching birds, including Thrushes, Tanagers, Orioles, Warblers, Finches, and Sparrows (Ehrlich et al. 1956). This narrowed the list to 159 species.
The weekly frequency checklist assigns an abundance level each week to each species. A species can be labeled as abundant, common, fairly common, uncommon, occasional, rare, very rare, or accidental. Species labeled as "rare" mean that they may be present, but are not seen most years. Species labeled as "very rare" mean that they are not present most years. Species labeled as "accidental" mean that there have been five or fewer reports of the species in 25 years. The next shortening of the checklist excluded all species that had assignments of rare, very rare, or accidental throughout the entire year of 2007. This narrowed the list to 111 species.