Geography Reference
In-Depth Information
community changes. This was evident in the Virginia woods studied by John
Aldrich, and it was striking to us as we counted birds around Seattle. Pacii c
wrens rule unsettled forests. In our reserves 14 percent of all birds were these
diminutive wrens. Nearly one of every two birds in forests was either a Pacii c
wren, chestnut-backed chickadee, Pacii c-slope l ycatcher, Swainson's thrush,
or American robin. During the early years of construction a new group takes
control. Violet-green swallows are the kings of this subirdia, accounting for
8 percent of all birds living in developments shortly after the start of construc-
tion. One of every three birds is a swallow, American robin, spotted towhee,
American crow, or chestnut-backed chickadee. As neighborhoods age, swal-
lows and robins remain atop the list of most abundant suburban birds. Grad-
ually, towhees and chickadees are bumped out of the top i ve by starlings and
juncos, such that in established subdivisions one of every three birds is a
swallow, robin, starling, crow, or junco.
It is a common feature of plant and animal communities, especially those
in temperate climates, to be composed of a few very successful species and
many very rare ones. This was evident to various degrees in each community
we sampled. As forests are settled, rare species accumulate substantially faster
than do successful dominants. Some of the rare exploiters and adapters are
just getting a foothold in new, suitable habitats. Other avoiders are barely
hanging on in the pieces of their former haunts that remain. Despite having
many rare species, common suburban birds share the wealth; the most com-
mon species included only about one of every ten birds we encountered. In
deeply urban places, such as the central business districts of large cities, this
is not the case. There, nearly every bird is a pigeon, house sparrow, or starling.
Not so in subirdia.
The changing nature of bird communities in our neighborhoods is a
quick reaction to the dramatic changes settlement brings to the land. I'll never
forget driving past a newly cleared lot just a few blocks from my home. I had
surveyed the birds on that lot four times each summer for the previous twelve
