Survival and reproduction of pen-reared vs translocated wild pheasants Phasianus colchicus
We compared vital rates of two different pheasant (Phasianus colchicus) stocks (pen-reared and wild) and assessed effects of predator control on these pheasants released into current range. Wild (31 males, 112 females) and pen-reared (230 males, 1,059 females) ring-necked pheasants were released in spring into two areas in southern Idaho during 2000 and 2001 to augment low resident populations. Wild female survival (value + 95% C. I.) from 1 March to 1 October was significantly greater than that of pen-reared females in both 2000 (0.40 + 0.14, N = 62 vs 0.04 + 0.07, N = 49) and 2001 (0.43 + 0.16, N = 40 vs 0.08 + 0.10, N = 40). Of 134 documented deaths of radio-marked female pheasants, 54% were due to unknown predation, 26% to mammalian predators, 12% to avian predators, 4% to natural causes, and 4% were human caused. Wild females had 0.50 + 0.22 (N = 20) nest success and 0.23 + 0.09 (N = 88) nesting rate while pen-reared females had 0.14 + 0.26 (N=7) nest success and a 0.28 + 0.18 (N = 25) nesting rate. Wild females produced 8.6 + 1.1 eggs/nest (N = 14) and pen-reared females 5.6 + 3.3 eggs/nest (N = 5). During 2001, predators were removed within our study areas. Survival of wild male pheasants increased after predator removal (0.20 + 0.35, N = 6 vs 0.70 + 0.28, N = 10) but survival did not increase for either stock of female pheasants after predator removal. Predator control did not increase the number of hens surviving to reach the nesting season (1 May), nesting rate, or nest success. Wild female pheasants were 7 times more likely to survive translocation to 1 October, 10 times more likely to survive to the nesting season, 8 times more productive, and one-third as expensive per egg hatched than pen-reared females. Low survival, poor productivity, and higher costs of spring-released pen-reared female pheasants strongly suggest that this is an inappropriate management tool for increasing pheasant numbers.
Key words: Phasianus colchicus, pheasants, survival, reproduction, pen-reared vs wild, translocation, predation, costs of releases