Troglodytes troglodytes – probable destructor of eggs of Cinclus cinclus

Interspecific or intraspecific destruction of eggs by other small bird species (Passeriformes) is a relatively rare behaviour. It is known from studies of several new world species from families Mimidae and Troglodytidae, but it has never been documented in the Eurasian wren (Troglodytes troglodytes). While studying the breeding biology of the white-throated dipper (Cinclus cinclus) in northern part of Central Slovakia, we documented seven events (frequency 1.8%) when Eurasian wren occupied a dipper’s nest during the breeding season. None of these breeding attempts by the dippers was successful. In all cases, the breeding pairs abandoned their nest. Except of these seven cases, we also found an abandoned nest (situated in the nest box under a bridge) with damaged eggs of the white-throated dipper. According to the intact nest bottom, we hypothesise that the nest was not predated. Here we probably describe the first case of egg destruction by the Eurasian wren in Europe.