. Bird populations in east central Illinois : fluctuations, variations, and development over a half-century. Bird populations. 34 Bird Populations in East Central Illinois 1974 (Johnson, 1975). These peaks and troughs agree well with fluctuations in the red-headed woodpecker population, except for 1963. Three-year moving averages were plotted (Fig. 10) to evaluate the possibility that competition between species may have caused peak populations to occur at different times. The starling was included because it competes with woodpeckers for nest cavities, usually successfully (Lohrl, 1956; Kilha
. Bird populations in east central Illinois : fluctuations, variations, and development over a half-century. Bird populations. 34 Bird Populations in East Central Illinois 1974 (Johnson, 1975). These peaks and troughs agree well with fluctuations in the red-headed woodpecker population, except for 1963. Three-year moving averages were plotted (Fig. 10) to evaluate the possibility that competition between species may have caused peak populations to occur at different times. The starling was included because it competes with woodpeckers for nest cavities, usually successfully (Lohrl, 1956; Kilham, 1958; Troetschler, 1976). Populations of common flicker and downy and red-bellied woodpeckers were all on the increase by 1953 or 1954. The red- bellied woodpecker reached a peak in 1956, and the downy woodpecker maintained relatively large numbers from 1955 i—I—i—i—i—i—I—i—i—i—i—|—i—i—i—i—(—i—i—i—r. 1950 Fig. 10. Three-year moving averages of breeding populations of four species of woodpeckers and the starling in William Trelease Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kendeigh, S. Charles (Samuel Charles), 1904-. Champaign : University of Illinois Press
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