Geography Reference
In-Depth Information
Rufous hummingbird
The Exploiters:
As the troubled avoiders winked out of new subdivisions,
seven exploiters replaced them. Included were the fab i ve cosmopolitans—
Canada goose, European starling, house sparrow, mallard, and rock pigeon—
plus two locals, the American crow and house i nch. Each species soared in
abundance as soon as clearing began and increased twofold to thirtyfold
during the next decade. All of these species are virtually nonexistent in forest
reserves. Crows, starlings, and i nches were rare at new neighborhoods im-
mediately after clearing began. The others did not colonize until three to i ve
years later. The ability of these species to capitalize on the lawns, lakes, and
nesting niches created in built environments likely explains their regional
success—all except the house i nch and house sparrow are stable or increas-
ing across western North America. Finches and sparrows may be declining in
response to factors beyond settlements, such as the socially transmitted dis-
ease conjunctivitis that af ects house i nches and the loss of small-scale agri-
culture that is of critical importance to house sparrows.
The Adapters:
Far and away the largest group of birds that responded to
development were those that adapted to new opportunities. Twenty-six such
species increased twofold- to one-hundred-fold during the creation of new
