. Bird populations in east central Illinois : fluctuations, variations, and development over a half-century. Bird populations. i—i—i—i—|—r W J ClosedM Forest/ A ^ i- Open Forest. Forest Edge ^-*- i* t~ Grassland J__i_ 1 I I I ' I 1950 1955 I960 1965 1970 Fig. 29. Three-year moving averages showing changes in number of breeding birds in different biotopes at Robert Allerton Park. Data for 1969 are averages for 1968 and 1969; for 1970, averages of 1969 and 1971. and field sparrow, and the most abundant OF species were mourn- ing dove and indigo bunting. Peak or near-peak numbers for many species
. Bird populations in east central Illinois : fluctuations, variations, and development over a half-century. Bird populations. i—i—i—i—|—r W J ClosedM Forest/ A ^ i- Open Forest. Forest Edge ^-*- i* t~ Grassland J__i_ 1 I I I ' I 1950 1955 I960 1965 1970 Fig. 29. Three-year moving averages showing changes in number of breeding birds in different biotopes at Robert Allerton Park. Data for 1969 are averages for 1968 and 1969; for 1970, averages of 1969 and 1971. and field sparrow, and the most abundant OF species were mourn- ing dove and indigo bunting. Peak or near-peak numbers for many species occurred in the mid 1960s, while a decline in numbers for several species occurred between 1969 and 1971. The larger popu- lations of FI species before 1952 rather than later was caused by overflow from large populations of American redstarts in the adjacent forest at that time (Appendix 3). The Complete Sere The increase in number of species and total populations correlated with succession of vegetation from fallow field to forest has been pointed out by Karr (1968). When the various census areas in this. 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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