Waterfowl (continued)

Unfortunately, increased sedimentation leads to increased turbidity, which reduces photosynthesis and therefore plant life. Increased sediments on lake bottoms also provide unstable surfaces for plants to anchor, further reducing plant populations. This loss of aquatic vegetation, coupled with the loss of species such as the fingernail clams lead to dramatic changes in waterfowl populations.

The mallard is one of the duck species that migrates in great numbers in the Illinois River valley. In December 1944, 3.85 million mallard and American Black ducks are documented on just seven lakes. In 1943, one researcher notes that “when all the other ducks are gone, there will still be mallards on the Illinois” (Havera 2002). Unfortunately, changes to the river are resulting in a continued downward trend for the mallard and other ducks.

Many species of ducks are affected by the decline in their food sources. This includes dramatic losses of aquatic plants in the 1950s, such as river bulrush (Figure 69), American lotus (Figure 70), marsh smartweed (Figure 71), and duck potato (Figure 72). A crash in the fingernail clam populations after 1954 also impacted other species.

Figure 69: River Bulrush
(USGS)

Figure 70: American Lotus
(Easy Living Native Perennial Wildflowers)

Figure 71: Marsh Smartweed
(Andy’s Northern Ontario Wildflowers)

Figure 72: Duck Potato
(botit.botany.wisc.edu)

The lesser scaup (Figure 73) occurs in tremendous numbers until the 1950s, when the fingernail clam populations crash (Havera 2002). The canvasback (Figure 74) also experiences similar declines, with 95,000 documented in 1953 but only 120 in 1971. Their populations are not recovering (Havera 2002). Table 47 illustrates the decline in the lesser scaup from 585,000 individuals from 1954 to 10,075 in 1957 and also the decline of the canvasback.

Figure 73: Lesser Scaup
(Arizona State University)

Figure 74: Canvasback
(Little Mesa House.com)

Table 47: Numbers of the Lesser Scaup and Canvasback (Starrett 1971)

Table 48 shows the decline of all diving ducks from 1946-1954 and 1955-1964.

Table 48: Diving Duck Population Declines in the Illinois River Valley* (Talkington 1991)

*Average number in each yearly census.

Two changes in agricultural practices have a detrimental effect on wildlife populations. First is the invention of the tractor, which unlike the “old dobbin” can plow steeper grades. This leads to the conversion of more lands to row crop agriculture. Second is the introduction of soybeans in the 1930s, which leads to the conversion of even more grasslands. Both changes result in increased soil erosion and sedimentation of the backwater lakes, reducing habitat for waterfowl and other species.