Geography Reference
In-Depth Information
pore. With so much to lose, tropical subdivisions will need to of er birds
much more than they currently do before they too can become subirdia.
Attaining and maintaining a rich avifauna are worthy goals for urban areas.
Birds, even nonnative parrots that have found their way into many temperate
cities, inspire people to care about other species. But enthusiasm for diversity
carries responsibility. It requires us to track worldwide changes and guard
against the loss of a region's distinctive life. House sparrows, European star-
lings, mallards, Canada geese, and rock pigeons—that fab i ve—live in nearly
every city around the world. Within a continent, the number of birds held in
common among cities is greater than the tally of cosmopolitans in less devel-
oped settings, such as forests or grasslands. This is the start of the homogeni-
zation process. By creating cities that birds view as similar—of ering the same
foods, plants, and arrangements of buildings and parks—we are starting to
erase the diversity that we can celebrate. So, while we cheer the parakeets
of Telegraph Hill, we should also recognize that they reduce the uniqueness of
San Francisco by increasing its similarity to tropical cities a hemisphere away.
To be a bird living among
Homo urbanus
is no small feat. It requires a
nimble nature with the ability to colonize new opportunities and persist when
the known world suddenly is transformed. As we celebrate urban diversity,
let's now take a close look at the dynamics of colonization and extinction. The
forest just beyond Seattle has changed in the short time I've studied its birds.
By going among the bulldozers, asphalt pavers, and nail gunners, my students
and I have watched many birds adjust and their populations soar. A few oth-
ers are less fortunate. As we consider how Pacii c wrens face up to the big and
hostile Bewick's wrens, or what happens when traveling juncos, robins, and
sparrows suddenly discover the riches of someone's yard, we can appreciate
how subirdia develops.
