Determinants of reproductive success in the Rufous Bush Robin (Cercotrichas galactotes)

Over a 3-year period, we studied determinants of reproductive success in a population of the migratory Rufous Bush Robin (Cercotrichas galactotes) par asitized by the Common Cuckoo (Cuculus canorus). Seasonal reproductive succ ess (as measured by the number of fledglings produced) depended on the numb er of successful broods raised. Many breeding attempts failed owing to pred ation, probably by cuckoos, which mainly affected first and replacement clu tches. Clutch size did not follow the general trend for multi-brooded speci es (mid-season peak), but showed a maximum early in the season, perhaps a c onsequence of delayed arrivals due to the negative effects of nest predatio n and parasitism through cuckoos. Interannual differences in several variab les of breeding success might be explained by marginally significant betwee n year differences in the number of nests depredated and/or parasitized. Br eeding success appeared to be independent of parental body size, but female condition (as measured by the number of light bands) had a powerful effect , with females in poor condition having less fledglings in the season, and lower fledging success (proportion of nestlings that fledged) and nesting s uccess (proportion of eggs that produced fledglings), than females in prime condition. Furthermore, age influenced breeding success, with old individu als producing more and heavier fledglings in the season than did yearlings. Poor breeding success or partner condition were unlikely to initiate divor ce, but rates of nest predation, which are probably linked to the male cont ribution in nest defence, appeared to increase the probability of divorce.