To monitor the status of waterfowl populations, the Michigan Department of Natural Resources (MDNR) began surveying abundance of breeding ducks and geese in 1991 and developed goals for waterfowl population and habitat management tied to the spring waterfowl survey. The spring waterfowl survey required flying a series of fixed-width transects using fixed-wing aircraft to estimate statewide abundance of Canada geese (Branta canadensis), mallards (Anas platyrhynchos), mute swans (Cygnus olor), and sandhill cranes (Grus canadensis) among others. To get consistent results, standard operating procedures (SOP) have been implemented and maintained across the years. Since observers did not see all birds from the fixed-wing aircraft, estimation of waterfowl abundance required surveying a portion of transects with helicopters to establish visibility correction factors (VCF). MDNR used the VCF to adjust fixed-wing estimates assuming observers saw all birds in transects flown with helicopters. To potentially improve precision and reduce costs, we developed alternate VCFs and aerial survey designs to understand how the accuracy and precision of the waterfowl population estimate changed from the existing SOP methodology. To meet MDNR standards, we considered alternate population estimates that produced a coefficient of variation (CV) of less than 20% to be acceptable and worth consideration. We found comparable population estimates and CVs from eleven alternate VCFs and three alternate aerial survey designs compared to the SOP.
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