Each week during fall and spring migration refuge biologists count waterfowl, shorebirds, wading birds, marsh birds and more to estimate the number of birds seen on the refuge. Survey numbers are used to describe general trends in the number of birds resting and feeding on the refuge through the years. Survey results are also used by managers, hunters and birdwatchers to monitor the progress of migration. Biologists use the number as a tool to assess bird use (often referred to as carrying capacity) in response to management actions. Bird use is influenced by off-Refuge factors such as continental populations and habitat and weather conditions throughout the flyway. On the refuge, food availability and the extent of human disturbance greatly influence the number of birds present.
Links to waterfowl survey information from National Wildlife Refuges along the Mississippi, Illinois and Missouri rivers.
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Dabblers include the ducks that tip their tail in the air as they submerge their head in the water to forage.