May Duck Breeding Population and Habitat Survey
This survey is the start of the "waterfowl year" in terms of data collection. The "year" will continue until the following March when sandhill cranes are counted. This aerial survey is conducted in the US and Canada and provides annual breeding population estimates for most duck species in North America, an assessment of breeding habitat conditions, triggering levels for harvest regulation through Adaptive Harvest Management and an assessment of population objectives in the North American Waterfowl Management Plan.
There are 49 strata (areas sampled based on habitat type and stability and waterfowl nesting density) in Canada, Alaska, North Dakota, South Dakota and Montana (see map) in which 1.3 million square miles (3.3 million square kilometers) are sampled (Waterfowl Population Status 2002). It costs $262,000 and takes 1,300 days to complete (Cooperative Migratory Bird Surveys in North America - 2002).
This survey became operational in the early 1950's and air/ground comparisons (aerial survey visibility corrections) in 1961 (Population Ecology of the Mallard I ). Thus the area covered is commonly referred to as the "traditional" area. This is to separate the survey from a similar one conducted to the east which became fully operational in 1996 and covers and additional 0.7 million sq. mi. (1.8 million sq. km). Additional surveys are conducted in British Columbia, Michigan, Wisconsin, Nebraska, Wyoming, Colorado and California.
In the Traditional Survey Area, the total breeding duck index excludes scoters, eiders, long-tailed ducks, mergansers and wood ducks. Typically, data is presented for 10 principal species (e.g., mallards, blue-winged teal, canvasbacks, scaup, pintails) of ducks which occur in the greatest abundance or for which specific management actions are taken. In the Eastern Survey Area, the total duck index excludes canvasbacks, redheads, ruddy and wood ducks.
Within each strata, the number of transects flown is determined by the density of wetlands and waterfowl that occur there (see map) - higher densities mean more transects are needed. The same transects are flown every year. Highly trained biologists/pilots (Flyway Biologists) count waterfowl on their side of the plane and an equally trained biologist observer counts waterfowl and ponds on the other. Flight altitude is generally between 100-150 feet and speed between 90-105 mph.
Technology plays an important role in data collection. Two laptop computers are mounted in the rear of the aircraft. They are wired into the aircraft power system and receive output from the aircraft Global Positioning System (GPS). As each bird or pond observation is recorded directly into a computer file via a microphone, the corresponding location from the GPS is automatically recorded. The GPS also makes it is easier today to stay "on transect". In the past, radio beacons helped in some areas but dead-reckoning was one art every pilot had to know. The "numbers" are transcribed each day into a new computer file by the Flyway Biologist.
Data collected for each strata along each established flight path or transect is:
The number of pairs, single ducks and ducks in flocks for each species
The number of "ponds" or wetlands with water.
These data allow the calculation of an annual index to the number of ducks for each species in the breeding population and habitat status.