Once waterfowl energy demands have been calculated, the next step is to determine how much energy is available to waterfowl in each habitat type on the landscape. First, the total acreage of various waterfowl habitats
must be quantified. In the past, this would have required tedious, land-based habitat surveys. Today it is accomplished via high-powered computers with special software used to map and analyze layers of geographic information (see "Quantifying Waterfowl Habitat
The second step in quantifying the waterfowl energy supply is determining how much food is available in various habitat types. Foraging habitats used by waterfowl ranging from agricultural fields to bottomland hardwood forests are sampled using a variety of techniques. Estimates are made of the biomass of seeds, submersed aquatic vegetation, roots, and tubers, as well as invertebrates and other animal foods. Data from recent research on waterfowl feeding habits are used to ensure that only important waterfowl foods are considered in these estimates.
The final step is to determine the energy values in the various foods waterfowl consume. This is usually accomplished by conducting experimental feeding trials on captive waterfowl. Test foods of a known quantity are fed to waterfowl held in metabolic chambers, where researchers capture all the birds' waste during a post-consumption fasting period. A method known as "bomb calorimetry" is then used to determine the amount of energy in the test food and collected waste. Subtracting the energy in the waste from the gross energy of the raw food provides an estimate of the amount of energy waterfowl are able to extract from each type of food. Together, the product of habitat acreage, food availability, and food energy provide an estimate of the total energy supply available to waterfowl in each habitat type.
By comparing waterfowl energy supply-and-demand data on key migration and wintering areas, DU and its partners can determine whether adequate foraging habitat is available to support desired waterfowl populations. Areas with foraging habitat deficits are targeted for additional habitat restoration and enhancement work. In places where adequate or even surplus foraging habitat exists, protecting the current habitat base is a top priority. Through these planning efforts, we can help ensure that waterfowl always have enough food during migration and in winter to survive and return to their breeding grounds in prime condition.
Quantifying Waterfowl Habitat Geographic Information Systems (GIS), supported by innovative computer hardware and software, and remote-sensing techniques have made it possible for waterfowl habitat managers to assess the extent and distribution of waterfowl habitat across vast areas. Ducks Unlimited and several partners are currently in the process of updating the National Wetlands Inventory, which will classify and digitally map all wetlands across the United States. This effort will also determine how many acres of each wetland type remain in key waterfowl breeding, migration, and wintering areas. In addition, GIS technology and remote-sensing techniques enable DU and its partners to monitor trends in wetland habitat quantity and quality on key waterfowl landscapes across the nation.
Dr. John Coluccy is director of conservation planning at DU's Great Lakes/Atlantic Regional Office in Ann Arbor, Michigan.