Beschreibung:
<p>Information on breeding duck abundance in the extreme southern portion of the Prairie Pothole Region has primarily been based on localized surveys utilizing ground counts of breeding waterfowl. Few attempts have been made to obtain regional estimates of waterfowl abundance in Iowa, and no attempts have been made to utilize helicopters to conduct surveys in this region. The purposes of our study were to estimate breeding duck abundance in northern Iowa and to evaluate a helicopter survey technique for this purpose. We conducted ground and helicopter surveys of waterfowl breeding pairs in Iowa in 1996 and 1997. Mallard (Anas platyrhynchos), blue-winged teal (A. discors), and wood duck (Aix sponsa) were the most abundant species. Both survey methods recorded similar numbers of breeding pairs of mallards and wood ducks each year, but helicopter surveys produced higher counts of blue-winged teal and other late-nesting species in 1997. Differences in late-nesting species were likely caused by temporal changes in pair numbers during migration. Visibility concerns for helicopter surveys were addressed using simultaneous helicopter and ground counts, and biases appeared minimal. Costs to conduct each survey were similar. Helicopter surveys provide a viable alternative to traditional ground counts in the southern portion of the Prairie Pothole Region.</p>