[tn-bird] City Birds Prefer Uptown
- From: "David Aborn" <daborn@xxxxxxxxxxxxxxx>
- To: <tn-bird@xxxxxxxxxxxxx>
- Date: Fri, 9 Aug 2002 08:39:01 -0400
ARIZONA STATE UNIVERSITY NEWS RELEASE
Embargoed until 9 a.m. PST August 8, 2002
Note: This research will be presented at a session at the Ecological Society
of America meeting in Tucson, Arizona on Thursday, August 8, 2002
City Birds Prefer Rich Neighbors
The rich have it all: better houses, better cars, better neighborhoods, and,
it now appears, better bird watching.
The Central Arizona-Phoenix Long Term Ecological Research Project has found
that the bird population has a slightly higher species richness (number of
species) and greater abundance (number of birds in general) in urban Phoenix
than in the surrounding Sonoran Desert, but the real surprise comes in a
recent study that shows that the city birds can be truly discriminating
about where they choose to live. The study's results indicate that bird
populations are influenced by economic factors -- more species live in
wealthy neighborhoods than in middle and lower income areas.
In a study of 15 small community parks located in Phoenix neighborhoods with
distinct socioeconomic classifications ranging from lower to upper income,
Arizona State University ecologists Ann P. Kinzig and Paige Warren measured
the abundance and diversity of both birds and trees. The researchers chose
parks rather than residential yards because these city-controlled spaces
offered comparable environments for the study sites, with a similar
landscape (grass, athletic fields, facilities and scattered trees) but
significant differences in the surrounding neighborhoods.
"What we are seeing is a pretty strong trend in the data," said Kinzig. "We
can't explain bird diversity in the parks by the size of the parks, or the
types or sizes of trees in the parks, which is what we might expect.
Instead, the characteristics of the neighborhood, including the income of
the residents, seem to play a significant role in influencing the number of
species that live in the park ."
Trees and other vegetation are considered to be a major factor affecting
bird populations. But the study's findings on diversity and abundance of
park trees, which are the primary vegetation in the survey sites, do not
correspond with the bird data. While bird populations were found to be most
diverse in upper income neighborhood parks and progressively less diverse in
parks in middle and lower income neighborhoods, tree diversity is actually
highest in lower income neighborhood parks.
The lack of influence of park vegetation is even clearer when the
researchers examined bird abundance (the total number of birds seen,
regardless of species), with summer bird abundance actually being
consistently lower where tree abundance is higher.
The lack of correlation between trees and the bird populations is important,
Kinzig notes, because the variety and number of trees planted are among the
few significant variables present in the make-up of the parks themselves,
and could be affected by economic factors. Tree landscaping is done by the
city, and could conceivably be influenced by the neighborhood's age and
economic status.
Though the study eliminates park landscaping as a factor, it does not yet
pinpoint specific explanations for how neighborhood economic status could
affect bird populations.
"Something that happens in the radius of 200 meters from the park
boundaries is influencing the diversity of birds," Kinzig noted. "Whatever
people are doing is having an influence, because we can't explain it with
the park itself. There's a variety of things - it could be what people are
planting, it could be socio-economic differences in how often you feed
birds, maybe the rich people have more bird feeders...
"It could be something as small as the feral and domestic cats and other
predators that live in the neighborhoods - not just how many people have
cats, but how many of them are prowling around wild and are good at catching
birds, or whether or not people put bells on their necks... Or it could be
zoning; what the city plants on the median strips; or how much industrial
and commercial activity is allowed," she said. "We don't know, but it's
something about the differences in people's lifestyle."
Though the mystery is hard to unravel, there are still some ecological
factors that Kinzig thinks could be relevant.
"We still want to look at reproductive success in the parks. There may be
something that's really influencing reproduction and that has an influence
on the bird community," she said.
"We'll look at food sources during the breeding season. What do people plant
in their yards that birds eat when they breed? Maybe some neighborhoods are
better than others for insects... we need to do arthropod surveys in these
areas. Maybe it's water... dog dishes are important water sources for
birds... maybe it's the distribution of dog dishes.
"We may not need to have all these absolute measures, but we need to learn
fundamentally how these neighborhoods differ from each other," she said.
"Cities are where people live now, and parks are going to provide their
daily access to nature. We have to understand what kind of nature people
will have in their parks, and what determines that."
The urban parks study is expected to continue for three more years, with
periodic updates thereafter.
For more information on urban parks research and on other research of the
Central Arizona-Phoenix Long Term Ecological Research Project, see
<http://caplter.asu.edu>
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