Referring
to an inner-city bird perched on a neglected dumpster as an
avian cockroach or feathered rat may well raise appreciative
nods. In fact, the ability of vast numbers of birds to make
their homes in cities regularly calls upon the ingenuity of
people to establish bird-free zones. This situation is not
restricted to North America. In Moscow, for example, to keep
Hooded Crows from sliding down renowned and easily scratched
gold-leaf on onion domes, recordings of falcons and Northern
Goshawks (the crow's major predators) were played and
trained falcons released. Animal rights activists
periodically disapprove of such niche-emptying efforts, but
when birds are in conflict with people, it is the avian
populations that are reduced and the human populations
appeased. But not all city dwellers
consider urban birds as candidates for extermination. More
and more people, in addition to those who enjoy feeding
pigeons and sparrows in parks, are viewing their avian
neighbors with interest. For birders who cannot often
venture into a natural setting there is a wealth of avian
activity to watch right in the city. Some urban birds become
uncharacteristically tame and relatively simple to observe.
It is easier, for example, to witness the maintenance of
dominance hierarchies in slow-gaited city pigeons (Rock
Doves) than in their fast-flying country cousins. Similarly,
city crows, park ducks, outdoor restaurant House Sparrows,
and parking lot Brewer's Blackbirds are more approachable
than their rural brethren. The artificial concrete and
steel ecosystems of cities, including occasional small,
manicured parks, can support a surprisingly large number of
birds. The birds are often most visible where people have
congregated to buy, sell, eat, and discard food. The
commensal relationship (whereby birds vacuum up bits of food
that people do not value for themselves -- items dropped,
discarded, or purposely provided) is evident near benches in
city parks, in playgrounds, sports stadiums, and the parking
lots of fast-food restaurants, at deserted farmers' markets
and fairgrounds, around refuse disposal areas, and at window
ledge feeders. Urban birds differ from wild
populations in several ways, besides just being easier to
observe. A number of ornithologists have looked at the ways
birds have adapted to urban foraging. For example, in cities
that lie in the snowbelt, birds may seek underground heating
ducts over which plants can grow, and have also learned to
feed in areas illuminated by artificial light where they can
prolong their foraging schedule. In another case, although
feral (country) pigeons usually eat twice a day, filling
their crops at each session and digesting the food between
the feeding bouts, city pigeons face a less predictable food
supply, and are much more opportunistic, having a relatively
irregular feeding schedule. Beyond foraging strategies,
however, we know little about other aspects of urban bird
behavior. Do different neighborhoods, for example, support
different dialects in House Sparrows? Do fluctuating
population sizes and uncertain resources cause changes in
avian behavior? Will, for example, group territoriality
eventually evolve so that gangs of grackles, European
Starlings, and blackbirds stake claims when the available
"turf" is limited? And how do fluctuations in the number of
city birds affect their avian predators? Domestic pigeons,
for example, are the favored prey of Peregrine Falcons. If
the number of pigeons is reduced, will Peregrines living
around urban areas resort to a different prey or suffer
substantial losses? In the 1940s a scarcity in feed led to
such a reduction in the German pigeon population and
resulted in a decline of Peregrines. As yet, however, no
parallel trends have been described or predicted in North
America. Urban habitats favor species
that are less affected by toxic substances flowing through
cities, that are better able to adapt to artificial light,
to communicate over the noise of traffic and automation, to
breed successfully on human built structures, and to rebound
after city council decisions to decimate their populations.
As more of the natural habitat of Earth is destroyed, urban
birds will become more "typical" of our avifauna. As
tongue-in-cheek evolutionists claim, birds may, indeed, be
feathered dinosaurs. Many species of birds may soon follow
the dinosaurs into extinction, but it seems likely that
urban birds will be around as long as there are people to
build cities. SEE: Helping
to Conserve Birds -- Local
Level;
Feeding
Birds;
Dominance
Hierarchies;
Population
Dynamics;
Habitat
Selection;
Commensal
Feeding. Copyright
® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl
Wheye.