People living in higher socioeconomic areas are likely to see a wider diversity of bird species in their parks, according to Paige S. Warren, who holds a joint appointment as a research scientist in the Department of Biology at Virginia Tech and the Center for Environmental Studies at Arizona State University. Warren is working on a study that eventually will provide information on how humans interact with and affect their environment.
Warren and two colleagues at Arizona State, Ann P. Kinzig of the Biology Department and Center for Environmental Studies and Chris Martin of the Department of Plant Biology, are investigating the relationship between socioeconomic level and the diversity of bird populations in urban neighborhood parks. Their work is part of the Central Arizona-Phoenix Long Term Ecological Research Project. Although there have been few studies of this sort, "it is well known that humans actively construct biological communities in their gardens, yards, and neighborhood parks," the researchers said in a summary of their study presented at the annual meeting of the Ecological Society of America.
The scientists studied 15 small Phoenix-area community parks whose surrounding communities had varying socioeconomic groups, from lower to upper income. They chose parks because they had similar characteristics but different surrounding neighborhoods. "We found that neighborhood socioeconomic status is the strongest correlate of bird diversity in these parks, even when other features of the park are accounted for," Warren said. "In other words, higher bird diversity occurs in upper-socioeconomic areas."
Conversely, they found that higher bird populations--usually of three major imported species (pigeons, European starlings, and English sparrows)--existed in middle or lower socioeconomic areas in cities. Although they have theories, they have not yet determined the cause of this phenomenon.
From five different locations in and around each park, the scientists counted the number of species and the number of individual birds. They also measured the structure of the vegetation in those parks. They then used stepwise regression, a statistical technique, to put in order of importance the possible explanations for a certain pattern of birds in the park.
They found that the lifestyle indicator, or socioeconomic status, was more important to bird diversity than the size of the parks or the types or sizes of trees in the parks as expected, according to Kinzig. In fact, they found that there were fewer birds where trees were more abundant. Lesser factors included the diversity of vegetation and the position of the park within the city.
The social characteristics considered included such things as income, food preferences, and cultural characteristics. "We think these will correlate with the landscape they create," Warren said, "the plants they put in their yards, bird feeders, bird watching, whether they have cats that roam." The height and types of vegetation and trees in the landscapes around the parks--whether it is of a native or imported variety, whether it is of a type that birds feed on, whether there are shrubs to vary the living space--all affect the bird populations, Warren said.
However, Warren said, the variation in bird diversity might occur through no fault of the people in the neighborhoods. "People have different preferences for different kinds of environments, but they may also have different abilities to realize their environmental preferences based on their income," she said. "The end result is that people in different neighborhoods have different access to nature in their neighborhoods and parks."
She and her fellow researchers are working with social scientists to find other indicators of social conditions. They will also look at other ecological characteristics that vary by neighborhood, such as the availability of insects that birds might feed on. They will combine the new information with the data they have collected already and are now analyzing. The immediate goal is to determine the differences in neighborhoods that account for the differences in bird species found there. The ultimate goal of the three-year study is to help determine the ways different human characteristics affect the environment.
PR CONTACT: Sally Harris (540) 231-6759 slharris@vt.edu
Researchers:
Paige Warren, 540-231-2715, pawarre1@vt.edu
Ann Kinzig at kinzig@asu.edu