For almost 40 years, the Division of Fish & Wildlife has conducted four waterfowl surveys annually to measure long-term trends in duck and goose populations. These surveys are carried out via a small plane with a pilot and biologist aboard, taking similar routes and using the same techniques each time. Each survey is flown using the same east-west transects to minimize data bias and allow for across year comparisons. Traditionally and as dependent on weather, flights were usually conducted in mid-October, mid-November, mid-December and the second week in January. The January flight coincides with the nation-wide mid-winter waterfowl survey conducted by the U.S. Fish and Wildlife Service. The traditional once-monthly state surveys cover most of the primary waterfowl habitat in Delaware, as identified by previous waterfowl biologists. The survey area approximately covers the eastern half of the state, and is divided into 11 zones. Since 2010, timing of the aerial surveys have been modified. They are now flown twice monthly, but only in the zones that coincide with greatest waterfowl abundances as identified from analyzing 40 years of survey data.
With any survey method, not every duck and goose can be seen equally well from a plane. The surveys give fairly accurate information about geese, due to their large body size. Some duck species such as wood ducks and sea ducks, are difficult to count due to the wetlands they inhabit or similar plumage characteristics.
Although imperfect, surveys are a useful tool for a waterfowl manager. The importance of conducting these counts and collecting this data provides strength to wildlife managers making informed policy decisions. Examples using long-term population trend data include setting season limits and dates and habitat management. In most cases no single survey count is especially important in itself, but cumulative counts have revealed important changes to waterfowl use of Delaware's wetland habitats over the years.
For example, the state's waterfowl surveys, along with similar surveys conducted in other Atlantic Flyway states, detected declining migrant populations of Canada geese in the 1990's; the reduced use of the Christiana marshes by ducks after Interstate 95 was constructed; and increases in duck abundances at Prime Hook National Wildlife Refuge after successful phragmites and water control. Winter counts are used as a measure of Tundra Swan and American Black Duck annual production. These data are also used in setting season frameworks for Atlantic Brant and other species.
Waterfowl counts are conducted within the following zones:
Zone 1 - Pennsylvania State line south to the Delaware Memorial Bridge (statewide).
Zone 2 - Delaware Memorial Bridge to the C&D Canal (statewide).
Zone 3 - C&D Canal to line from Liston Point to Kenton (statewide).
Zone 4 - Liston Point to Route 6 Smyrna (statewide).
Zone 5 - Route 6 Smyrna to Route 8 Port Mahon (statewide).
Zone 6 - Route 8 to Big Stone Beach, east of Route 113.
Zone 7 - Big Stone Beach to Broadkill River, east of Route 1.
Zone 8 - East of Route 1 from Broadkill River to Lewis-Rehoboth Canal, south of Gordon's Pond.
Zone 9 - South of Gordon's Pond and all of Rehoboth Bay.
Zone 10 - All Indian River Bay west to Millsboro and south to Salt Pond.
Zone 11 - Salt Pond south to Maryland state line and west to Route 17.
Waterfowl Survey Data
Waterfowl Survey Data from 1974 to present can be viewed at http://dnrec.alpha.delaware.gov/dnrec-open-data/
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