Scaup (bluebills) — this one trapped and banded Thursday along the Illinois River — were once among the most populous ducks in North America. Then their population crashed, which is why Illinois is holding the largest effort to band them. | Dale Bowman~Fo
Updated: April 18, 2013 6:34AM
LEWISTOWN, Ill. — In camo neoprene waders, a dozen biologists and researchers waded out at Emiquon Preserve on Thursday morning to a trap filled with scaup (bluebills).
One sealed the funnel on the trap with PVC pipe. Others opened the back wire; two netters scooped scaup. Nets were carried to a boat where birds were stashed in poultry crates for transport.
One scaup-trapping oddity is that males are caught at a 10-to-1 ratio. The best guess is predation on females during nesting exacts a heavy toll.
It’s not a subject to dabble in — you have to dive in.
In the late 1940s, as many as 750,000 scaup (bluebills) filled the Illinois River around Peoria, Steve Havera said.
What happened? Once one of the most populous ducks in North America, scaup began a slide in the ’70s, then, mysteriously, a bit of a return recently.
Illinois has been at the forefront of waterfowl study for more than a century, as Havera, author of Waterfowl of Illinois and senior professional scientist emeritus for the Illinois Natural History Survey, pointed out.
Naturally, Illinois is in the forefront of scaup-banding. For years, Al Afton of Louisiana State University has banded a couple of thousand lesser scaup annually on Pool 19 on the Mississippi River. The Diving Duck Ecology Project in the Illinois River Valley, overseen by Heath Hagy, director of Forbes Biological Station for the Illinois Natural History Survey, does 1,000 annually.
I was happy when Eric Schenck, Illinois regional biologist for Ducks Unlimited, invited me to observe.
Banding begins with trapping using a bigger version of a minnow trap. There’s a funnel into a wire cage, baited with corn. It’s set in deeper water to attract divers like bluebills more than dabblers like mallards. Once birds swim in, they are trapped.
The crew — from the Illinois Department of Natural Resources, INHS, The Nature Conservancy and the U.S. Fish and Wildlife Service — first gathered at the boat launch at Emiquon. Meeting at Emiquon was no accident; it’s TNC’s great restoration/experiment on the Illinois River backwaters.
‘‘Two years ago, duck-use days for pintails was the highest ever for the Illinois River Valley — same with green-winged teal,’’ said Tharran Hobson, river program restoration manager for TNC.
I love the idea of Emiquon and try to visit at least once a year.
As we set out in two boats, more than 10,000 snow geese took off. The first two traps were empty. The third held 60 or 70 scaup, veteran INHS research biologist Michelle Georgi estimated.
Many questions surround bluebills. Why do fall migrations bring few along the Illinois River, but the spring migration has significant numbers?
‘‘Biologically, spring migration might be just as important because we want them to get to the breeding grounds in good condition,’’ Hagy said.
On Wednesday, Schenck organized a dinner with Hagy, myself and Randy Smith, wetland program manager for the IDNR. They had a discussion ranging from hydrology to human/duck interactions to human/human interactions for so long that we outstayed the last customer at Bistro 101 in Canton by an hour.
I asked why scaup declined. Nobody knows for sure. Maybe double-counting on the migration north or failure to adjust nesting starts to global warming (canvasbacks are nesting more than a week earlier) or possibly five population spikes skew the average.
The next stop Thursday was crossing the river to check traps along levees at Chautauqua National Wildlife Refuge. The first had more than 100, the next about 70 and the final dozens. Researchers had more than enough.
It was time.
Schenck handed me a scaup to see up close. It was like staring back at history and into a mystery.