A little over a week ago, the late July Illinois River level was holding steady at about 12.9 feet, which is more than several feet above its normal low level at this time of the year. My hope was for falling river levels. So I was not happy with the high water. While a spring flood is a normal part of the river’s yearly pattern of highs and lows (hydrology), by late July into August and September, the expectation is for relatively steady, low levels, which would expose mud flats in the many floodplain lakes that flank and are connected to the river. These flats attract migrating shorebirds, the objects of my attention at this time of year.
A favored vantage point for observing shorebirds is on the upper end of Quiver Lake, an Illinois River backwater, where my small, rustic cabin is located. Typically, I’ll find a shady spot along the shore to set up a spotting scope, and then leisurely wait for the birds to show up. But Quiver Lake is directly connected to the Illinois River; so when the river’s level changes, as it usually does, the same happens to Quiver Lake. Even in August, I cannot always count on seeing mud flats.
And yet, according to the National Oceanic and Atmospheric Administration (NOAA), the river’s level is projected to gradually fall through at least the middle of August. If this does, indeed, happen, then the lake bottom will eventually be exposed all around the lake’s periphery. And if the river continues to fall, mud flats from more exposed lake bottom will expand in area and become an irresistible target for shorebirds.
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Since my observations about a week earlier, the river has fallen over five feet. Along the mainland shore of Quiver Lake, sandy seeps have become exposed, feeding pure groundwater to the lake and river. Elsewhere, further out, there are narrow strips of mud along the shoreline. The bulk of the lake, though, is still open water. From a quick scan of the shoreline, I counted 50 great egrets in the shallows, about a third as many great blue herons, and a few killdeer, but no other shorebirds. Yet I know that they are in the area, because at nearby Chautauqua National Wildlife Refuge, which is along the northern boundary of Quiver Lake, observers on July 27th noted 20 shorebird species (from the Illinois Birders Exchanging Thoughts web site, posted on July 27, 2016 by Colin and Sharon Dobson). Shorebirds were at the refuge because within the levee system (an earthen walled enclosure) refuge managers have kept water levels low so that mud flats are exposed and marsh vegetation can grow.
For the time being, I will remain patient and hope that our regular summer drought period begins and river levels continue to fall and then somewhat stabilize. An examination of NOAA‘s data from recent years, however, leaves some doubt that this will happen. For example, last year the river topped out at 27.24 feet on July 1st, breaking the 1943 record of 27.10 feet; and the previous year, it crested at 17.34 feet on July 5th and crested again at 14.36 feet on September 13th. River levels are, of course, directly related to precipitation. And according to the Illinois State Water Survey, this year’s July was the third wettest on record for Illinois (7.12 inches). Another year that stands out in memory is 2008; I vividly recall the summer of that year, when July turned out to be the 10th wettest on record (see chapter 19, “As the Rivers Rise Again” [ Download Chapter 19 - As the Rivers Rise Again] in my book Side Channels). In recent years, only 2012 provided good shorebird habitat at the Quiver Lake bottoms; but that year also presented Illinois with severe drought conditions.
Quiver Lake, September 23, 2015 during medium water levels.
It has always been give and take along the Illinois River. Boaters prefer the river at higher levels, so obstructions are kept well under water. For fishing, lower levels might be better, with fish more concentrated at habitat structures that still remain submersed. Birders looking for shorebirds should prefer the lowest river levels throughout the late summer season, before marsh vegetation grows too high; but at that point, countless flowers will provide nectar sources for migrating monarch butterflies; and in the fall, seeds from maturing vegetation will attract thousands of migrating ducks. At the same time, one summer flood can overwhelm all of the shorebird habitat and severely set back vegetation growth.
Quiver Lake, 28 July 2012 during low water.
And though each year is unique, I look forward to witnessing these natural repeating patterns from year to year, which are still evident despite all of our modifications to the river and its floodplain. And that is what I intend to do in my folding lawn chair, in the shade along Quiver Lake, while waiting for the mud.