Forbes Biological Station

01/09/2026

Weather kept us out of the air much of the week, but we were able to sneak in the mid-winter inventory of the Illinois river on the afternoon of Wednesday, January 7 2026. Unfortunately, we did not get a flight in on the Mississippi river this week. Duck abundance (94,750) was right on par with the long-term average (94,129) on the Illinois this week. Mallard abundance in the IRV was less than observed last week (-13%) but right on par with the LTA for this week. The partial ice thaw has spread our remaining birds out on the landscape, which I what I attribute to this slight decline. At the risk of repeating observations from last week, mallards, black ducks, and common mergansers were significantly above their LTAs for this time of year. The remaining species of ducks, however, have all but moved out of our region.

A welcome sight, snow and white-fronted geese were abundant this week compared to what we typically observe at this time of year. The drastic difference in abundance should come as no surprise considering the above average temps, lack of snow cover, and strong south winds we've experienced the last few days.

Fingers crossed for better weather next week!

01/07/2026

Bring your tots to Dickson Mounds to learn about waterfowl from Forbes staff, Dr. Abigail Blake-Bradshaw!

Join us this Thursday, January 8, at 9:30 a.m. for Tot Time!

This month’s program is all about ducks and will be presented by staff from Forbes Biological Station. Participants will enjoy learning about how the waterfowl live, what they eat, and why they are important to the environment. Tots and caretakers, expect to enjoy hands-on activities and crafts to take home!

The program will begin at 9:30 a.m. and is free. Registration is not required. However, groups of 8 or more are encouraged to call the Museum at 309-547-3721 prior to the program date to ensure the availability of supplies. Participants are welcome to enjoy the Museum exhibits after the program.

Photo of Forbes staff holding a hen mallard with a transmitter

01/06/2026

Happy New Year! We flew the first waterfowl survey of 2026 on Friday, January 2, 2026. Duck abundance was slightly lower than the long-term average on the Illinois (-4%) but greater than LTA on the Mississippi river (+33%) this week. Mallard abundance was greater than LTA on both rivers this week, +19% and a whopping +60% on the Illinois and central Mississippi, respectively. As the ice coverage persists, mallards continue to be the most abundant. Indeed, 90% of the observed ducks observed in the IRV were mallards, while that comparison was 72% for the central Mississippi this week. Those mallard estimates this week are ~225,000 mallards on the MS river, and ~82,000 in the IRV. Notably, almost every other species was below LTA in our survey area this week. The consistent ice coverage combined with the early snow seems to have moved most non-mallards out of our region.

A much used photo, but still my favorite. Something I haven't done lately is to highlight the history of our survey. This will be a longer one...

In the fall of 1938 Dr. Frank C. Bellrose began traveling by car and boat with binoculars and a spotting scope to record waterfowl abundance from various vantage points in the Illinois River valley. Bellrose initiated experimental aerial inventories in the fall of 1946, when pilots, planes, and fuel became available after World War 2. He noted that the time required to inventory the Illinois Valley was reduced from a week to a day and that a large part of the Mississippi Valley could be included in the one-day flight. Frank began consistently surveying waterfowl from the air in 1948, and this is what we consider the beginning of our dataset.

Approximately 214 miles of the Illinois River, from Hennepin to Grafton, and 272 miles of the central Mississippi River, from Grafton to Muscatine, are aerially inventoried for waterfowl weekly from September through early January.

The purpose of these aerial surveys is not to acquire complete counts of waterfowl within specific geographic areas but to estimate the number of each species in order to provide an index of temporal changes within and among years and to document the distribution and abundance of species throughout our region. An added benefit of the inventory is to provide information to refuge managers and waterfowl hunters along both rivers. This information aids in conservation planning and delivery at critical habitat along the Illinois corridor of the MS Flyway. Because of the efforts of the INHS with the long-term support of the Illinois Department of Natural Resources, the annual inventory data on numbers and distribution of migratory waterfowl in Illinois is unequaled.

We aerially inventory 23 locations on the Illinois River and 18 locations on the central Mississippi River weekly. Flights are generally scheduled for the earliest "good weather" day of the week beginning in early September and lasting until mid-January. Once a flight is completed, we post results as soon as possible.

We start the inventory shortly after sunrise from the Pekin, IL area and head south counting waterfowl areas all the way to the confluence of the Illinois and Mississippi River near Grafton. From Grafton, we head up the Mississippi River counting refuges in Illinois and Missouri and arrive at the Quincy, IL airport sometime between 11:00 AM and noon. After refueling the airplane and grabbing some lunch, we proceed up the Mississippi River to the Port Louisa Refuge near the Pool 17 Dam. We then fly east, back to the Illinois River and resume counting waterfowl at Hennepin and proceed south and finish counting ducks at the McClugage Bridge at the narrows of Upper Peoria Lake and Lower Peoria Lake.

The long term nature of the inventory and consistency of survey methods over the years adds to the strength of this data. We count the same locations, week after week, year after year, at approximately the same time of day, by a limited number of observers. In fact, there have only been 5 observers over the 76 years of aerial inventories. Bellrose was the observer until 1970, Tud Crompton took over until 1989, Michelle Horath flew until 2004, and Aaron Yetter took over in 2005. I took the reins in 2021, a responsibility I do not take lightly.

Our data has been used to conduct peer-refereed research, aid in conservation planning, inform season structures, target areas of value during various field work, among many other things. The survey and it's observers have been witness to the decline of duck populations and the ever-continuing efforts to bring them back.

For this week's numbers and more information about the survey, see the website link in our bio...

12/24/2025

Merry Christmas! We flew the waterfowl survey on Monday, December 22, 2025. Just a touch of thawing and small distribution changes this week. I suspect things will really open up over the holidays! With the winter solstice behind us and the photoperiod changing, I wonder if many of these birds will just "risk it for the biscuit" and try to stick it out here for the rest of the winter. Duck abundance was lower than the long-term average on the Illinois (-10%) but greater than LTA on the Mississippi river (+17%) this week. Though I did observe fewer mallards on the Illinois river this week compared to last, I estimated near the same number of mallards this week on the central Mississippi river as I did last week. Those mallard estimates this week are ~230,000 mallards on the MS river, and ~100,000 in the IRV, 7% and 49% greater than LTAs, respectively. It is worth noting that we observed several holes in the ice near the main channels of the rivers held open by ducks last week. This week, ducks appeared to have left those holes and found their way back into refuges. Duck season is over in the North and central zones, but at least we still have geese to pursue.

I hope your holiday season is filled with time afield, a good dog, family and old friends, quite mornings, fond memories, and gratitude. Oh, and good food too.

For this week's numbers and more information on the survey, please visit our website. The link is in our bio. Merry Christmas and Happy Holidays from the Forbes Crew!

12/17/2025

We flew the waterfowl survey on Tuesday, December 16, 2025. The bitter cold combined with the snow over the weekend here in central Illinois has changed the landscape and pushed some ducks, mostly divers, out of our region. With the previous exit of non-mallard dabblers, that leaves mostly mallards, goldeneyes, and common mergansers to count. And, of course, the geese. Duck abundance was lower than the long-term average on both the Illinois (-7%) and Mississippi rivers (-31%). However, there wasn't an apparent movement of mallards out of our region as many expected. Concentrated though they may be, we estimated ~230,000 mallards on the MS river, and ~140,000 in the IRV this week, both figures well within striking distance of their respective long-term averages. Indeed, mallards in the IRV were estimated 13% greater than LTA for this week. We did, however, lose our diving ducks, especially those on the MS river. A rough "back of the napkin" calculation suggests that we lost over 200,000 divers this week on the MS river alone. Those near the usual haunts of divers on the MS river have no doubt noticed their absence.

"Tis the season for migration discussions. Many hunters down south are experiencing earlier than usual success due to the cold, snowy winter the Midwest has experienced thus far. If you grow weary of the back and forth about this topic on social media, I recommend you do some digging into the Weather Severity Index models published by Dr. Mike Schummer's lab. With over 10 years of analysis into decades long datasets, the WSI shows that duck migration tends to be a threshold-driven, energetics-based response to cumulative weather stress. The index takes into consideration minimum air temp, snow depth, and duration of freezing conditions. I'm simplifying drastically here but, birds "tolerate" moderate cold but move rapidly and cover large distances once WSI crosses limits that restrict food availability. This response varies by species, habitat conditions, and foraging strategy. Its also increasingly dynamic due to the highly variable climate conditions we find ourselves in these days.

For better or worse here in Illinois, northern zone duck season is over and our closer here in the central zone is drawing ever closer. Hopefully the thaw in the coming days will move some birds around for some eleventh-hour opportunities.

12/12/2025

We got back in the air for the waterfowl flight on Tuesday, December 9, 2025. Many thanks to Aaron Yetter for filling in for me this week. More ice and and a seemingly final last exodus of non-mallard dabblers was apparent during this week's survey. Duck abundance was lower than the long-term average on the Illinois (-35%), but greater than LTA on the Mississippi river (+10%). Diving ducks, especially canvasbacks, are still very abundant on Pool 19 of the MS river, between the Keokuk dam and Montrose. Total duck abundance was estimated at 131,555 in the IRV, and 588,780 in the CMRV.
One more weekend for our northern zone hunters and another week and a half for the central zone. Conditions are tough, but hopefully many are finding a way to get out there and pursue the mallards and divers that remain. Best of luck to those still on the hunt as well as those who have already started field hunting geese.

12/06/2025

And just like that the ice is here...