Woody Habitat and Severe Winter Mortality of Ring-Necked Pheasants in Central Illinois

Abstract

Ring-necked pheasant (Phasianus colchicus) populations declined 44-82%, primarily from exposure to precipitation and severe wind chill, in the severe winters of 1976-77 and 1977-78 on 5 study areas in east central Illinois. Pheasant abundance, estimated by cock-call counts, and woody vegetation were measured on 45 1,036-ha subunits during 1976-78. Multiple regression analyses indicated no relationship between pheasant abundance on the 45 subunits before or after severe winter weather, and the abundance, growth forms, or arrangement on the landscape of woody vegetation. Declines in cock calls, 1976-78, were a mathematical function of pheasant densities prior to severe winter weather (r = 0.94, P < 0.001). J. WILDL. MANAGE. 46(4):923-932 Currently, the intensively tilled Mollisols of central Illinois (Fehrenbacher et al. 1967:40) afford little residual cover to protect ring-necked pheasants from winter elements. Robertson (1958:19), however, noted that the occurrence or abundance of pheasant populations in the east central counties was not related to the presence of woody or herbaceous vegetation in winter. Labisky et al. (1964:12) also noted that direct losses of pheasants in Illinois to winter weather were rare. Robertson (1958:18-19) attributed the low winter mortality of pheasants in Illinois, compared to most Plains states, to abundant scattered waste grain and mild winters with infrequent blizzards. In 1963 and 1964, however, dead pheasants were observed following winter storms near Sibley, Illinois. Following a severe winter storm in Illinois in January 1977, Warner and David (1978) found 27 frozen pheasants along 64.4 km on 1 study area, 5.6% of the known prestorm population. Subsequent census data indicated a storm-related decline of 54-67% (Warner and David 1978:117). These authors necropsied 49 of the birds found frozen and reported that 40 (82%) had food (principally corn and soybeans) in their crops and 39 (80%) had normal reserves of body fat. These findings were consistent with the observations by Robertson (1958) and Kenyon (1978) that scattered waste grain has been generally available to wintering pheasant populations in the Midwest. The objectives of our study were to document the magnitude of storm-related declines of pheasant populations on 5 study areas in central Illinois in January 1977 and winter 1977-78, and evaluate the importance of woody vegetation to the survival of pheasants before and after those severe winters. We acknowledge J. C. Cole and W. H. Wood, Illinois Department of Conservat on (IDOC), for assistance with censusing. L. S. Gerstein, Illinois Natural History Survey (INHS), assisted with habitat analyses and data tabulation. J. H. Moak and J. A. Ellis (IDOC) read the manuscript. S. L. Etter, W. R. Edwards, and G. C. Sanderson (INHS) provided technical and editorial assistance and E. Steger (INHS) edited the manuscript. The research was funded by Illinois Federal Aid in Wildlife Restoration Projects W-66-R and W-85-D, the Illinois Natural History Survey, the Illinois Department of Conservation, and the U.S. Fish and Wildlife S rvice, cooperating. J. Wildl. Manage. 46(4):1982 923 This content downloaded from 207.46.13.28 on Wed, 31 Aug 2016 04:39:50 UTC All use subject to http://about.jstor.org/terms 924 WOODY HABITAT AND WINTER MORTALITY OF PHEASANTS -Warner and David