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Conspecific brood parasitism (CBP) is a reproductive tactic whereby a parasitic female lays its eggs into the nests of other conspecific females. Genetic-based data on the occurrence of CBP in birds, however, is still relatively scarce. We analysed prevalence of CBP in a ground-nesting diving duck, the common pochard Aythya ferina, using a set of 17 microsatellites. Compared to related species, our population showed a relatively high level of CBP, with 39% of genotyped pochard eggs laid parasitically and 89% of nests containing ≥ 1 parasitic egg. In addition, we observed relatively high rates of interspecific brood parasitism (13% of eggs), caused predominantly by mallard Anas plathyrhynchos and tufted duck Aythya fuligula. CBP eggs had decreased hatching success compared to host eggs, with 65% of CBP and 95% of non-CBP genotyped eggs hatching successfully. Our data suggest that this was probably due to improper timing of parasitic egglaying, which compromised synchronised hatching of CBP and host-eggs. Despite high rates of CBP in our pochard popu lation, fitness costs associated with this reproductive tactic appear to be low for host females since neither clutch size nor host-egg hatching probability were reduced due to CBP.