A Critical Review of the Aerial and Ground Surveys of Breeding Waterfowl in North America.

摘要: Abstract : The U.S. Fish and Wildlife Service the Canadian in cooperation with others have conducted an annual survey of breeding waterfowl throughout central Canada, north-central United States, Alaska since 1955. area comprises more than 50 strata habitats. Ducks are counted from aerial transects, counts adjusted upward to account for birds that not observed by crews. These adjustments, called visibility correction factors, developed on ground during which all assumed been detected. Counts made a subsample survey. Visibility factors calculated each species crew. total number ducks is then as product density, factor, strata.