Most studies of birds in urban areas have reported a decrease in avian species richness and/or diversity in association with urbanization, although density typically increases. In the southwestern United States, the greatest diversity of breeding birds is normally found in riparian habitats (areas surrounding rivers or lakes). It is estimated that the bird diversity in riparian zones surpasses that of all other western habitat types combined.

In a region characterized by low rainfall and often sparse vegetation, riparian zones act as an oasis for both migratory and resident birds, offering a relative abundance of the critical elements of water, food, and cover. Natural riparian systems are quickly disappearing, however, in response to the demands of a growing human population on these areas for water, recreation, and development, as well as degradation due to factors such as flood control efforts and improper grazing practices. Estimates are that up to 95% of western riparian habitats have been lost or degraded over the past century, and many of the bird species associated with these systems have been driven out or have experienced severe declines.

SOUTHWESTERN GOLF COURSES

Given the extensive loss of riparian systems throughout the West and the potential similarity of habitats on golf courses to those of riparian areas, we were interested in determining whether golf courses might possibly serve as surrogate riparian habitats for breeding birds in the Southwest. We hypothesized that golf courses in the Southwest would not only have greater avian species richness and abundance when compared to the surrounding natural environment, but that the golf courses would also support a greater number of bird species normally associated with riparian areas. The goals of our study were to determine: (1) how the presence of a golf course impacts the native bird community through comparisons of abundance, species richness, diversity, evenness, and productivity between five golf courses and five undisturbed reference areas assumed to represent the original bird communities; (2) whether golf courses support high numbers of typically riparian bird species; and (3) if possible, identify those features of golf courses that are most conducive to supporting high numbers of native and riparian bird species.

STUDY SITES

Our study sites were five golf courses and five paired reference sites in the high desert region of Albuquerque, New Mexico. Courses were chosen to represent a range of vegetation types, course features (e.g., water sources), and landscape settings. The participating golf courses were the Albuquerque Country Club (ACC), Four Hills Country Club (FH), Paradise Hills Golf Club (PH), PaaKo Ridge Golf Club (PK), and University of New Mexico Championship Course (UNM).

A paired reference site was selected for each golf course. Reference sites were nearby natural areas that reflected, as much as possible, the habitat conditions that would have been present prior to the construction of the companion course. The purpose of these reference sites was to provide an avian community baseline. Birds on the reference sites were assumed to represent the original bird community for its paired golf course.

RESULTS OF THE TWO-YEAR STUDY

Golf courses supported a greater number of birds than surrounding natural areas, a response that is common throughout studies of avian responses to urbanization. In contrast to many such studies, we also found increased avian species richness on most of the golf courses, as well as increased diversity. The increase in avian abundance on golf courses was to a large degree at the expense of more specialized native bird species, as has been witnessed in numerous other studies of urbanization effects. We found that a relatively few widespread and abundant species made up the majority of individuals detected (including, but not limited to, house sparrows, house finches, common grackles, and European starlings), comprising from 69% to 76% of the individuals detected on three out of the five courses.

Species richness of native birds was greater on golf courses, in contrast to the results of many other studies of birds in urban environments. This result held across all five of the courses we studied. The abundance of these native birds was not as great as that of cosmopolitan or introduced species, but golf courses supported numerous native bird species that were not components of the avian community in the surrounding natural areas. Of birds that were exclusive to our golf course observations, 54 (83%) were native species that we did not consider to be cosmopolitan or introduced species.

Furthermore, we found strong support for our hypothesis that golf courses would provide habitat for riparian birds. More than 70% of the species observed exclusively on golf courses were riparian associates. The numbers of individuals in this group were relatively low, particularly once we excluded those that are also considered cosmopolitan species (e.g., American robin). Still, 25% of the birds observed on golf courses were riparian associate species that were not represented in our samples of the surrounding natural area bird communities.

Our results add support to the hypothesis that avian species richness and/or diversity does not respond to urbanization in a linear fashion, but instead peaks at a level of intermediate disturbance or development. At the higher levels of urbanization, most of the land area is dominated by buildings or paved areas, and any vegetation is primarily ornamental. Golf courses, however, represent an intermediate level of development in which most of the land area is still vegetated, some areas of native habitat may remain, and trees and ponds are common. Habitat diversity may actually increase under such a scenario, as structural diversity is added through changes in vegetation as well as the introduction of buildings and other structures that may serve as nest sites or perch sites, and openings are created for edge species. Moderate levels of development may increase food resources for some guilds of birds. Scavenging opportunities increase, and areas of lawn or turf are capable of supporting high numbers of ground-foraging birds.

GOLF COURSE OASES IN THE DESERT LANDSCAPE

This potential increase in habitat diversity at low to moderate levels of development is particularly noticeable in the desert landscape. In general, there is a strong positive correlation between bird species diversity and habitat diversity such that any increase in habitat diversity, particularly in a relatively simple landscape such as a desert, is likely to result in increased species richness. The features added to the landscape during the development of a golf course often stand in sharp contrast to those of the desert environment. Courses may provide numerous shade trees, water sources, turf, structures, and vegetation types that are not available in the surrounding natural areas.

The impact of a golf course on avian community composition in the desert environment appears to be very different from that of one that may be constructed, for example, in a forested area. In other studies, increased development in hardwood forests led to a loss of canopy-foraging or bark-gleaning birds, since canopy trees were lost from the habitat. This is consistent with the observation that the loss of bird diversity is likely when development occurs in an area that had an initially high diversity of habitats.

ECO-FRIENDLY CHARACTERISTICS OF PAAKO RIDGE

In addition to increased habitat diversity, the greater native species richness at PaaKo, and the continued dominance of its avian community by native species is likely attributable to the extensive areas of undisturbed native vegetation on the course. Increased numbers of native bird species and the ability to exclude invasive avian species are associated with the amount of native vegetation present.

WHAT WE LEARNED

Golf courses in the high desert area of Albuquerque have the potential to support large numbers of native bird species. In addition, the resources and habitat diversity provided on these courses may mitigate, to some extent, the loss of riparian systems in the Southwest. However, the conservation value of golf course habitats in this desert region could be improved to support greater numbers of native birds and exclude more invasive exotics or pest species by increasing the complex vertical structure and diversity of plant species composition in the out-of-play areas on the courses, and, in particular, by increasing the extent and usage of native plants. Such improvements, even on a very small, localized scale, have the potential to effect changes in bird species composition, and golf courses that are dominated by native vegetation may support significant numbers of native bird species.

Our data showing increased species richness of native birds, and particularly high numbers of riparian species on these courses, demonstrate that these golf courses may be capable of providing valuable stopover habitat for the numerous species of migratory birds that utilize riparian corridors in the Southwest. The potential for desert golf courses to serve as surrogate riparian areas for these species has important conservation implications, as many migratory birds in the western U.S. are currently experiencing population declines associated with the loss of riparian habitats.

Editor's Note: For a more complete report of this research, including comparative tables of observed bird species, methodology, and graphs of the results, visit the USGA's Turfgrass and Environmental Research Online at http://usga-tero.msu.edu/v04/n14.pdf. TERO publishes the results of studies funded through USGA's Turfgrass and Environmental Research Program.

Michele Merola-Zwartjes, Ph.D., and John P. Delong, Ph.D., USDA Forest Service, Rocky Mountain Research Station, 333 Broadway SE, Suite 115, Albuquerque, NM.