November 1, 2018

Illinois’ Flying Waterfowl Biologist

Photos by Aaron P. Yetter

“Up, up, and away,” says the pilot over the noise of the propeller and the wind whipping by at a brisk 160 mph. Three days each week during fall and early winter, Illinois Natural History Survey (INHS) Biologist Aaron Yetter counts ducks, geese and other waterbirds along the Illinois and Mississippi rivers. Yetter pivots sideways in his seat, placing his face against the cockpit window as the plane rapidly descends toward the backwater lake. “1000, 500, 2000, 300…” counts Yetter out loud as the airplane swoops overtop of large and small groups of birds.

INHS has conducted aerial surveys of waterfowl and other waterbirds each fall since 1948 forming the longest running aerial waterfowl inventory in North America.

“Our waterfowl inventories are used by state and federal agencies to set hunting regulations and season dates,” said Yetter. “Scientists also use our data to evaluate habitat restoration projects and illustrate the effects of environmental processes, such as climate change.” This research is supported by the Illinois Department of Natural Resources through Federal Aid in Wildlife Restoration administered by the United States Fish and Wildlife Service.

Yetter joined the INHS in 1992 and became the primary aerial waterfowl observer in 2005, taking over duties from veteran Michelle Horath, who spent 15 years in the cockpit.

Single prop plane flying in blue sky

“Since 1948, only four observers have conducted our waterfowl inventories which is important for data consistency,” noted Yetter, who received his Bachelor and Master of Science degrees from Southern Illinois University Carbondale. His graduate project explored wetlands and waterbirds in the Chicago suburbs and outlying areas in northeastern Illinois. Since joining INHS, Yetter has worked on and led many research projects in Illinois. In addition to the aerial inventories, his work has included spring-migration ecology and food habits of lesser scaup and canvasbacks; fall-migration ecology of mallards; historical and contemporary characteristics of Illinois River Valley wetlands; mallard and wood duck nesting ecology; artificial nesting structures; moist-soil management; seed abundance at waterfowl management areas; spring foraging thresholds of waterfowl; shorebird food habits; colonial nesting of great blue herons and great egrets; aerial monitoring of water hyacinth; and, aerial inventory of nesting bald eagles and great blue herons in Illinois.

When asked if he ever gets airsick, Yetter grinned from ear to ear, “maybe from time to time; it takes a while to train your pilot.”

The public is always curious about the waterfowl survey and Yetter’s standard response when asked if he flies the planes: “Heck no, I’m looking at the water—someone has to watch where we are going.”

A single prop plane flying in the sky with waterfowl flying scattered around the plane.

How do you count the birds? Yetter responds, “You get an idea of what 10 ducks or 100, 1,000 or 5,000 ducks look like, then you estimate their numbers in blocks.” Yetter likes to make his first pass at the birds from about 300 feet to get total numbers, then he buzzes lower to separate the species. “Sometimes I have to make them fly so I can see their wings to identify them, especially early in fall when they aren’t in full plumage,” he added.

When asked what his biggest wildlife-oriented accomplishment is, Yetter reflects back over his 25-year career. “If I had to pick one,” he said, “it would have to be my involvement in the 66 year waterfowl survey in Illinois. Just knowing that I am continuing a project initiated by Frank Bellrose is quite humbling. Our data is used extensively in Illinois and across the country.”

A wetland with trees in the background and a single-prop plane flying in the sky.

Aaron P. Yetter is a biologist for the Illinois Natural History Survey, Prairie Research Institute and Heath M. Hagy served as the Director of INHS’s Forbes Biological Station.

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Question: Where can I find a current Illinois Waterfowl numbers update.