Geography Reference
In-Depth Information
Because the adapters we studied rely on the removal of dense forest cover
to produce open lands for grasses, shrubs, and the rich mosaic of resources
found along forest edges, they also decline in abundance as such “early suc-
cessional” habitats mature and revert to forest. Any early successional habitat
that was on a Breeding Bird Survey route in the 1960s would gradually lose its
appeal to our adapters as it became more of a forest and less of an opening or
edge. Only with new disturbance—a i re, severe wind, l ood, or volcanic
eruption—would forest be converted back to habitat adapters favor. The odds
are simply stacked against seeing an increase in adapters at any given location—
maturation is certain, but disturbance is not. So by returning to the same loca-
tion each year to count birds, as is done to estimate regional trends, it is almost
inevitable that adapter numbers will go down, as will the proportion of routes
that cover recently disturbed ground. This does not necessarily mean adapters
are declining in other places; where there is disturbance, they should l ourish.
A better assessment of population trends for adapters would come from
standardized counts during the summer months in many cities and other nat-
urally disturbed areas. The only such count is the annual tracking done by
Project FeederWatch. In this ef ort, citizens count the birds they see in their
yards and report the results to scientists at Cornell University's Laboratory of
Ornithology. Tens of thousands of “citizen scientists” participate in this ef ort
each year. Although some of our adapters are not evaluated through Project
FeederWatch, most of those that are have increasing or stable population
trends. Three species—pine siskin, rufous hummingbird, and song sparrow—
are declining at feeders as well as along Breeding Bird Survey routes.
As the population of some birds increases and that of others decreases during
the construction of a neighborhood, the relative makeup of the entire bird
