clock menu more-arrow no yes

Filed under:

Ice cometh/goeth, bad day for coots, mallard anomaly: Illinois Natural History Survey aerial survey

The early-week icing certainly impacted the weekly aerial waterfowl survey by the Illinois Natural History Survey, plus Joshua Osborn’s blog includes a mallard anomaly and a bad day for American coots.

A bad day for American coots at Port Louisa. Credit: Joshua Osborn/Illinois Natural History Survey
A bad day for American coots at Port Louisa.
Joshua Osborn/Illinois Natural History Survey

Joshua Osborn observed in his blog off flying the aerial waterfowl survey for the Illinois Natural History Survey the significant drop in ducks around the Illinois River, probably related to icing early in the week.

Most of the observed decline in numbers can be attributed to the less cold-tolerant pintail, green-winged teal, gadwall, and shoveler.

In a similar vein, he noted:

Mallard numbers stayed relatively constant in the IRV this week, dropping by only 6%. The ice cover appeared to move ducks around looking for open water, changing the distribution in the IRV.

Click here for details on the aerial waterfowl inventories and the long history of them. Click here for the home site for the Forbes Biological Station; click here for the Facebook page of the station.

The overview and blog of the latest aerial waterfowl survey by Osborn, a waterfowl ecologist for the INHS-Forbes Biological Station, is below:

We flew the waterfowl survey on Tuesday, December 7, 2021. We encountered lots of ice this week, especially along the Illinois River. In fact, we discussed trying to fly later in the week to get a better snapshot of what was left after the ice thaws through the middle of the week. Unfortunately, the weather just did not look good for a flight on Thursday or Friday. I estimated ~213,000 ducks along the Illinois River this week, a marked decrease (-38%) as compared to last week’s estimate and 5% below the 10-yr average for this river. Most of the observed decline in numbers can be attributed to the less cold-tolerant pintail, green-winged teal, gadwall, and shoveler. Mallard numbers stayed relatively constant in the IRV this week, dropping by only 6%. The ice cover appeared to move ducks around looking for open water, changing the distribution in the IRV. We counted more ducks on Duck Creek, Big Lake, and Upper Peoria Lake than last week. I estimated ~622,000 ducks in the central MS River this week, 14% above the 10-yr average. Illinois’ upper MS River refuges had similar ice issues as the IRV this week, but ice was less of an issue on the lower portions of this river. Refuges near the confluence appeared to pick up mallards this week, while also holding onto many of the non-mallard dabblers. It will be interesting to see how the birds move around as this ice thaws.

I’ve attached two pictures this week. One from Port Louisa to show what a bad day looks like for American Coots [at top]. And the second is a mallard anomaly from the private refuge at Dardenne [at bottom]. Enjoy!

As always, thanks for the support!

Here is the breakdown of the numbers:

IL120721.pdf

MS120721 (1).pdf

A mallard anomaly at the private refuge at Dardenne. Credit: Joshua Osburn/Illinois Natural History Survey
A mallard anomaly at the private refuge at Dardenne.
Joshua Osburn/Illinois Natural History Survey