INTRASPECIFIC NEST PARASITISM AND ANTIPARASITE BEHAVIOR IN THE GREY STARLING, STURNUS-CINERACEUS

I studied intraspecific nest parasitism in the grey starling Sturnus c ineraceus in 1992 and 1993. The population in this study consisted of 290 nests (157 nests in 1992 and 133 nests in 1993) in which the clutc hes were completed before May 10 in the year studied. Twenty-nine nest s in 1992 and 32 nests in 1993 contained at least 1 parasitic egg. Hat ching success per nest of parasitized nests was slightly higher than t hat of non-parasitized nests. However, fledging success per nest of pa rasitized nests was significantly lower than that of non-parasitized n ests. Thus parasitism appeared to reduce the reproductive success of h osts. Hosts exhibited a few behaviors that minimized the potential cos t of brood parasitism. These behaviors included throwing out the paras itic egg and nest guarding. Hosts threw out-parasitic eggs before the onset of laying, but they never did so to parasitic eggs laid after th at period. The nest guarding level was low during the hosts' laying pe riods, and one observed nest was parasitized during this time. Thus, n est-guarding behavior was not effective as an anti-parasite behavior. Grey starlings do not appear to adopt strategies effective in reducing parasitism.