Geography Reference
In-Depth Information
Australian researchers suggested that increasing native vegetation, especially
on the ground and among the shrubs, may reverse Perth's losses, much as was
the case for London.
The long-term transitions at places like Lake Barcroft, inner London, and
Kings Park reveal slight changes in the membership of bird communities and
substantial changes in the abundance of the birds that remain throughout a
period of urbanization. In all cases, the birds that were most common before the
expansion of urban or suburban lands declined in numbers, while a set of those
that were initially rare increased. In Virginia, for example, the wood thrush
held thirty-one territories in 1942, but only two in 1979. In contrast, the num-
ber of cardinal pairs during this time increased from i ve to thirty-eight. Dr.
Rob Blair, a pioneer in the study of urban birds and professor at the Univer-
sity of Minnesota, categorized species by such responses to urbanization as
avoiders, exploiters, or adapters.
Avoiders are those species that are extinguished or decline precipitously
over time as urbanization intensii es. In the eastern United States, some avoid-
ers are the forest specialists such as the red-eyed vireo, ovenbird, and wood
thrush. In western Australia avoiders are the ground pouncers. In London
they are the cavity nesters such as the jackdaw and species with special needs
such as the skylark, wryneck, and nightingale. What we do—pave, turf, light,
pollute, fragment, disturb, and make noise—they cannot tolerate.
Adapters, on the other hand, are mostly native species that thrive on natu-
ral young, open, shrubby, and dissected native habitats. They i nd and adjust
to these situations in our cities and towns, even if the natural habitat is only
approximated by the built condition. Adapters are tramps easily dispersing
across our world. If they were plants, we'd call them weeds. They live fast,
prodigious lives and die young. Their natural strategy is to track environmen-
tal disturbance—they are the i rst to colonize lands perturbed by hurricanes,
i res, tsunamis, or glaciers. Because our cities produce and maintain the sort
of features that follow disturbance—grassy meadows, brushy slopes, or rocky
