On February 11, 2010, I posted an essay called “The Missing Red-headed Woodpeckers of Sand Prairie-Scrub Oak Nature Preserve,” which can be found under the category “Birds and Birding” along the left panel of this weblog. Sand Prairie-Scrub Oak Nature Preserve is located in Mason County, Illinois, about 8 miles south of Havana. I wrote that essay because I felt that after monitoring the overwintering red-headed woodpeckers at the nature preserve since 2003, and finding significant numbers each winter, it was a noteworthy observation that during the 2009-2010 winter, they were nearly absent. I knew that their overwintering populations were closely tied to the amount of oak mast (acorns) available, and I speculated that the woodpeckers would eventually return, especially during a fall season with widely abundant mast. Such a fall occurred in 2010, and the red-headed woodpeckers did, indeed, return. A similar relationship with mast availability can also be seen with blue jays.
The table below (click on "View this photo") shows all of the bird count data that I collected at Sand Prairie-Scrub Oak Nature Preserve from 2003 to 2011. The population crash and recovery is evident for both red-headed woodpeckers and blue jays by examining the seven counts conducted between 20 October 2007 and 26 January 2011. It is also significant, I believe, that the number of species and individual birds counted on 1 February 2010, when zero red-headed woodpeckers were encountered, were the lowest (7 species, 19 individuals) of all of the 16 counts made in between 9 November 2003 and 26 January 2011.
