Evaluation of Proximal Primary Feather Criteria for Aging Wild Pheasants

Abstract

Wild Illinois pheasants (Phasianus colchicus) captured in fall and winter, 1969-70 and 1970-71, and separated into juvenile and adult age-classes on the basis of bursa depths, were used to evaluate proximal (innermost or Number 1) primary measurements as age criteria. The proximal primary shaft diameters (PPSD) of 307 cocks, collected during fall, separated into juvenile and adult age-classes at 3.210 mm (0.1264 inch) with 92 percent reliability. A sample of 46 cocks, collected duxing winter, separated with 98 percent reliability at the same measurement. In a sample of 285 hens captured during fall, the separation point occurred at 2.908 mm ( 0.1145 inch) with 90 percent reliability. However, in a sample of 234 hens taken during winter, separation occurred at 2.858 mm (0.1125 inch) with 92 percent reliability. The reliability of PPSD as separation criteria could not be enhanced by taking into account the lengths of the proximal primaries. Oven-drying of proximal primaries was necessary to obtain repeatable measurements. Mean PPSD of juveniles of both sexes were significantly larger in the fall than in the winter, whereas those of adults showed no signi$icant difference. The fully grown PPSD of juveniles of both sexes, as measured in fall, were positively correlated with their estimated hatching dates. The PPSD of adults were inversely correlated with their estimated dates of molt initiation. Although there was no apparent explanation for seasonal differences in PPSD, the smaller PPSD of juveniles in winter suggested lower fall-to-winter survival rates of late-hatched juveniles (with large proximal primaries), compared with early-hatched juveniles. Dorney and Holzer ( 1957 ) used the diameter of the ninth primary shaft as a criterion for estimating the age of ruffed grouse ( Bonasa umbellus ) cocks in spring. Wishart (1969) extended this technique to game-farm-reared ring-necked pheasants, using the proximal (Number 1) primary because juvenile pheasants, unlike grouse, replace the outer two (Numbers 9 and 10) juvenal primaries during their post-juvenal molt (Wright and Hiatt 1943). The purpose of this paper is to evaluate the application of this technique to wild Illinois pheasants. Evidence will be presented on the possibility of age-specific differences in fall-towinter mortality. We thank W. R. Edwards, C. M. Nixon, Dr. G. C. Sanderson, and Helen C. Schultz 1 A contribution from Illinois Federal Aid Project W-66R, the Illinois Department of Conservation, the U. S. Bureau of Sport Fisheries and Wildlife, and the Illinois Natural History Survey, cooperat-