This story was originally published in the March-April 2005 issue of the Green Section Record
Urbanization, roads, and other human-induced changes to natural areas continue to alter and degrade wetlands nationwide. As natural wetlands decline in availability and quality, alternative habitats such as created wetlands may become increasingly important to wetland-dependent wildlife. Wetland-dependent birds, often referred to as waterbirds, seem well suited to use created wetlands when appropriate habitat is available.
In urban and suburban areas, golf course ponds have excellent potential to provide valuable habitat in areas that otherwise lack suitable habitat for waterbirds. Anyone who has spent time on a golf course has noticed a variety of birds such as ducks, geese, herons, and the little peeps running along pond shorelines. It seems clear that many species of waterbirds use golf course ponds. What is unclear, however, is what characteristics of golf course ponds are important for waterbird species.
Studying Florida Golf Courses
A two-year study (2001 and 2002) in southwest Florida was conducted to determine the habitat value of golf course ponds to waterbirds. Our objectives were to identify the diversity and abundance of waterbirds using golf course ponds and to evaluate the effects of numerous habitat variables on waterbird use. Habitat and hydrological variabIes were quantified at each pond to determine the relationship between these components and waterbird abundance and species richness. Hydrological variables included trophic status, as an indicator of food availability, and available able shallow water (1.3 feet) habitat around each pond's perimeter. Habitat features included shoreline and littoral zone vegetation type and cover, and adjacent landscape features (e.g., golf course, residential housing, construction, ete.).
All species studied in this project were waterbirds and are defined as any water-dependent bird species." Members from the following orders of birds were surveyed: Ciconiiformes (wading birds), Gruiformes (short-legged and other wading birds), Pelecaniformes (diving birds), Anseriformes (waterfowl), Podicipediformes (grebes), Coraciiformes (kingfishers), and Charadriformes (shorebirds). Birds from these orders represent a variety of bird sizes, morphology, foraging techniques, and major substrate used for foraging (e.g., bare mudflat vs. open water). Because the degradation of wetland habitat has affected nearly all species of wetland-dependent birds, it is important to consider more than one species when determining the functionality of created ponds on golf courses for waterbirds.
Therefore, all waterbird species observed in the ponds or within 5.5 yards of pond edges were included during surveys. Species were categorized into six foraging guilds, defined by their major foraging techniques, food types and substrates listed for each species as well as personal observations of foraging birds on golf course ponds. Foraging guilds were used in the analysis of waterbird site selection because there were normally too few observations to conduct separate analyses for each species. Twelve golf courses were surveyed during this study, nine owned by Bonita Bay Group and three by Watermark Communities Incorporated. All golf courses were located in Lee or Collier County in southwest Florida.
Golf courses were selected to provide a diversity of study sites within the study area without previous knowledge of the quality or nature of habitat associated with ponds on those golf courses. A total of 183 golf course ponds from these 12 courses were monitored during the study. Annual surveys were conducted during January through April.
This study focused on birds that were actively using golf course ponds; therefore, only waterbirds observed in the water or within five yards of the water's edge were recorded. Birds that flew over ponds but were not obviously foraging or did not stop at the pond were not included in the analyses.
Shorelin~ vegetation is important for many foraging and nesting birds, as well as for birds seeking shelter and protective cover. During this study, shoreline vegetation was delineated by the pond's waterline because the centers of the ponds were generally too deep to allow growth of vegetation other than purely aquatic plants. Percent cover of shoreline and aquatic vegetation was visually estimated. Percent cover class was used to quantify visual estimates of vegetative cover, which was classified into seven terrestrial and four aquatic categories.
Measurements of the landscape features adjacent to the ponds were taken simultaneously with the shoreline vegetation. The effective foraging area within the littoral zone was quantified to determine its influence on site selection of golf course ponds, particularly by wading birds (e.g., herons and egrets).
Four water-chemistry parameters were measured to determine the tropic status (i.e., biological productivity) of golf course ponds: water clarity and total chlorophyll a, phosphorus, and nitrogen.
Lots Of Waterbirds Recorded
During January-April 2001 and 2002, 10,474 waterbirds were observed during surveys of 183 man-made ponds on 12 golf courses. We observed 42 species of waterbirds (30 in 2001 and 40 in 2002) over both years. The most common behaviors of all birds observed were associated with foraging, and the least common with nesting activities.
Approximately 46% of all waterbirds observed used golf course ponds as foraging habitat. The remaining 54% also may have used the golf courses as foraging habitat, but they were engaged in other activities (resting, preening, etc.) during surveys. The diving birds guild was the most commonly recorded. Anhingas (in 2001) and double-crested cormorants (in 2002) were also observed on more study ponds than any other species. The second most frequently observed guild was Open Water, with little blue herons (Egretta caerulea) most abundant over the two-year study period. The dense vegetation wader guild was observed least.
Larger Ponds, More Waterbirds
The major objective of this study was to determine the influence of pond characteristics of bird use. Differences among golf courses may have due to variables that were not easily captured by analyses, but may have included differences in human use, management practices or locations of the courses relative to other resources that were not quantified during this study (e.g. distance to nesting colonies). However, we did analyze the influence of the total pond surface on each golf course (versus the surface area of individual ponds) on waterbird use and found a significant relationship, indicating the total pond surface area explains some of the variation in average bird abundance among golf courses.
Several major factors appeared to influence waterbird use of golf course ponds at the landscape and individual pond scale. Golf courses with more total pond surface area had more birds on average. Greater pond surface area (in the form of larger or more numerous ponds within the same golf course) may provide advantages such as reduction of effort required of the birds when moving among ponds to find food.
At the individual pond scale, pond size influenced waterbird use by 4 of the 6 foraging guilds. Larger may be able to provide more foraging opportunities and habitat types to support a greater diversity of waterbirds. This relationship has been reported for birds in other freshwater habitats.
However, availability of food, the most crucial feature for determining foraging habitat suitability for waterbirds, includes not only density but accessibility of suitable prey. Many waterbirds are unable to access prey in open-water areas. For example, wading birds and shorebirds are confined to water depths no greater than their leg length. Indeed, the effective foraging area was a better predictor of pond use by the majority of wading birds (open-water waders) than either surface area or perimeter.
Observed differences in bird presence among golf courses may also be related to the golf course location relative to other landscape features important to waterbirds, such as natural wetlands, flooded pastures and roosting or nesting areas. Once a golf course has been selected, birds may then select from available ponds within the course based on more specific pond features such as pond size or vegetation structure and density.
Analysis of waterbird site preference for other pond features resulted in a wide range of habitat variables selected by each foraging guild. However, several similarities exist among the selected variables. For example, trees and shrubs provide roosting and resting habitat for several foraging guilds. Short vegetation in the littoral zone and along the shoreline of the ponds was selected by several foraging guilds, probably because it allowed for increased predator detection while foraging. Ponds with man-made structures such as walls and ledges around the perimeter were avoided by one foraging guild (dipping and dabbling foragers) probably because they impeded movement into and out of the water.
The large number of species of waterbirds observed during this study indicates that golf course ponds are used by many different types of waterbirds, principally as foraging habitat (46%). The extent to which waterbirds used golf course ponds in this study was primarily related to pond size, ability of the birds to access prey and habitat features that influenced security and foraging success. The low densities also suggest there is ample opportunity to increase the value of golf course ponds to waterbirds.
Opportunities For Habitat Improvement
The wide range of habitat variables selected by each foraging guild indicates that providing a diversity of habitat features among ponds within a golf course would provide the greatest benefits to the largest number of species. To accomplish this goal, ponds could be managed as a wetland complex, whereby different ponds or sections of ponds are enhanced or modified to meet guild-specific needs. For example, creating areas along ponds that have dense shrub cover would benefit dense-vegetation waders, trees can provide roosting sites, and the creation of shallow foraging areas will benefit wading birds and numerous other species.
Not only would this type of management strategy benefit waterbirds, but it could also provide greater management options for the golf course. Maintenance problems associated with wet areas along edges of ponds may be ideal for modifications to benefit waterbirds while simultaneously reducing management costs and maintenance challenges. Consequently, opportunities likely exist on many golf course ponds to improve habitat for waterbirds while providing financial savings and generating positive public relations for practices that provide benefits to wildlife.