Geography Reference
In-Depth Information
were too small to carry even the lightest radio tag. So, we banded (ringed)
nearly two hundred of them and crashed through the brush, among the bull-
dozers, and between the new rows of houses hoping to i nd our marked nee-
dles in the proverbial haystack. This sort of mark-resighting study is common
among ornithologists, but we'd be the i rst to use it to track the movements of
birds in response to human settlement.
To catch each wren, we lured them into i ne-meshed “mist” nets that we
placed strategically throughout their territories. We quickly removed the en-
tangled wrens and kept them calm in soft, dark bags as we prepared to ai x to
each of their tiny legs a unique combination of colored plastic rings. A uniquely
numbered aluminum band issued by the federal Bird Banding Laboratory
would accompany these color bands. The combination of bands gave each
bird a personal identity that we could see with binoculars, thereby allowing
us to note its place of residence without having to catch it again. It takes only
a few minutes to tag each wren, and then the hard work begins.
Just as John Aldrich mapped the territories of forest birds in Virginia, we
now mapped every location where we encountered each wren—banded or
not—in each of our developing subdivisions, forest reserves, and established
neighborhoods. Over the next twelve years we mapped more than seven hun-
dred territories and determined how their placement varied from year to
year. Though we tagged many wrens and studied many more territories, we
resighted barely half of the breeders in reserves and only a third of them in
developing subdivisions. Annual losses were high, in some instances because
of death and in others because of the movement that so intrigued us.
An annual mortality rate of 50 percent is not unusual for small birds
such as wrens, so the birds we failed to i nd in forest reserves likely perished
from natural causes. The greater disappearance rate in developing suburbs
suggested heightened mortality, greater movement, or some combination of
both. Kara gave us good evidence that at least some wrens l ee development and
settle on distant territories where they continue to breed. All the wrens we
