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Counting ducks from 500 feet above: How a wetland bird ecologist inventories waterfowl along the Illinois and Mississippi rivers

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Forbes Biological Station
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Blue and green-winted teal and northern pintail seen on the Illinois River during an aerial waterfowl inventory over Chautauqua National Wildlife Refuge in Havana.

Josh Osborn has a unique job. The Navy veteran turned ecologist leads the waterfowl aerial inventories from the Frank C. Bellrose Waterfowl Research Center at the Forbes Biological Station in Havana.

Taking to the skies every autumn and spring during migration seasons, Osborn makes regular educated estimates of the number and types of birds flocking along 212 miles of the Illinois River and 214 miles of the Mississippi River.

"We fly something like 32 weeks out of the year. So this is obviously only a portion of my job. But it's in the science world, we always say we stand on the shoulders of giants. And that's never more obvious than when you get to work with a dataset like this," said Osborn.

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Illinois Natural History Survey
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Waterfowl ecologist Josh Osborn of the Frank C. Bellrose Waterfowl Research Center at Forbes Biological Station in Havana manages the aerial waterfowl inventories along the Illinois and Mississippi Rivers.

Osborn is just the fifth ecologist since 1948 to lead the aerial waterfowl surveys. The migration surveys along the Illinois and Mississippi rivers date back to the 1930s, with aerial surveys beginning in 1948 under the leadership of Frank Bellrose.

"Our aerial survey data represents the longest known inventory of waterfowl, and actually it's been going on longer than the U.S. Fish and Wildlife Service's breeding waterfowl counts up on the prairies, and longer than the midwinter inventories, which were started in the '50s," said Osborn. "So it's super important data set, (a) super unique data set, as something that covers an important part of the migration."

The work can be taxing. Osborn can spend eight to nine hours a day up in a low-flying plane flown by Mike Cruce of Pekin. He's become experienced at tallying up the number of birds gathered at survey sites along the rivers.

"When you get into the seven, eight hundred thousand birds, you're not counting every single bird. You're getting a really close estimate, and getting as close as you can to as many birds are there. So it's more of a more of a trend analysis, population analysis kind of data set," Osborn said.

Osborn said he's frequently asked how he can even begin to estimate when that many waterfowl are gathered in one spot. His predecessor, Aaron Yetter, had this standard reply:

"Aaron's favorite response was, you just count their feet and divide by two," Osborn laughed.

But in all seriousness, Osborn said he began to get a good gauge on the number of birds on the water from five hundred feet up.

"You get an idea of okay, this is what, depending on the density of birds, this is what 100 birds looks like, this is what 1,000 birds looks like," he said. "And you just kind of you go from there and extrapolate over the entire area."

Various types of geese and ducks are among the most common waterfowl Osborn sees, but they're far from the only species. Bald eagles, swans, pelicans, and double-crested cormorants are also among the bird species which migrate along the waterways.

The long-term nature of the migratory data allows the scientists in Havana to analyze trends over the last several decades.

"We've got a quantitative ecologist here now. We've kind of all collectively been working on a dataset, or working on this dataset, incorporating some climate data to see if we can see how a changing climate has changed the migration chronology of birds," he said.

Osborn said he's proud to lead the aerial waterfowl inventory.

"It can really take it out of you, but to get to see how waterfowl and and other birds kind of distribute themselves on the landscape is pretty rewarding," he said. "And to get to see a lot of the things that we study and has been studied in the past, to get to see that stuff play out over time throughout fall and spring migration every year, it's pretty fun."

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