Parasitism of Greater Prairie-Chicken Nests by Ring-Necked Pheasants

Abstract

We studied nest parasitism of greater prairie-chickens (Tympanuchus cupido pinnatus) by ringnecked pheasants (Phasianus colchicus) as a possible contributing factor in the decline of an isolated population of prairie-chickens in Jasper County, Illinois. Both species nested in small, scattered grasslands maintained on prairie-chicken sanctuaries. Incidence of parasitic laying by pheasant hens in prairie-chicken nests increased from 2 to 43% between 1970 and 1983 and remained high through 1987. Nest success (:1 host-egg hatching) did not differ (P = 0.33) between 60 unmanaged parasitized nests (43%) and 602 unparasitized nests (51%). However, success of 14 parasitized prairie-chicken nests managed by removal of pheasant eggs (86%) was greater (P = 0.02) than for 24 unmanaged parasitized nests (46%) during 1983 and 1985-87. Hatchability of fertile prairie-chicken eggs was less (P < 0.01) in parasitized nests (77%, conservatively) than in unparasitized nests (94%), because of earlier hatching of pheasant eggs, increased embryo mortality of prairie-chickens, or increased nest abandonment. Large clutches of prairie-chicken eggs typical of early nests were more likely (P < 0.001) parasitized than small clutches laid later. Factors correlated with rate of nest parasitism included numbers of pheasant cocks (P = 0.01) and numbers of pheasant nests (P < 0.001) found each year. Although pheasant control apparently eliminated nest parasitism during 1988-94, prairie-chicken numbers continued to decline. Without management intervention to control pheasants on sanctuaries, the survival of this isolated, remnant flock of prairie-chickens may be in greater jeopardy.

Beyond the beneficial effects of translocations as an effective tool for the genetic restoration of isolated populations

“…Our estimates of nest success showed similar trends, with a considerable decline from 70% (95% CI = 62-78%; n = 312 nests) for the period 1963-1972 to 51% (95% CI = 44-58%; n = 547 nests) between 1973 and 1987, and a reported rebound to 55% (n = 20 nests) following the 1992-1996 translocation period (Walk 2004). Predation by mammals, birds and snakes, and nest parasitism by ring-necked pheasants (Phasianus colchicus) have shown to have direct impacts on nest abandonment and egg hatching success (Berger et al 1962;Hamerstrom et al 1964;Vance and Westemeier 1979;Westemeier et al 1998b). The implementation of management activities aimed at decreasing levels of predation and nest parasitism did not result, however, in significant increases in population size (Walk 2004).…”

Interspecific brood parasitism in galliform birds

“…Parasitism rates increased from zero prior to the presence of Pheasants to 29% of host nests during years of peak Pheasant density. In some study areas within the larger population, annual IBP rates exceeded 50% (Westemeier et al. 1998).…”

Two grouse clutches in the same nest: evidence for nest site adoption in capercaillie (Tetrao urogallus)

“…As pointed out for waterfowl, however, joint clutches may simply occur as a result of nest-site competition, without a need for evolutionary explanations such as parasitism or adoption (Eadie et al 1988;Erskine 1990). A shortage of nest sites also appears plausible to explain cases of interspecific nest parasitism (Westemeier et al 1998).…”