Elevated noise is likely to participate in species decline in urban areas. By disrupting vocal communication, it may be a major factor explaining impaired reproductive success of birds. However factors impacting reproductive success are diverse in urban areas and conclusions are hard to draw. To better understand the relationships between noise, reproductive success and vocal communication, we lack investigations on bird species that evolved under constraining natural environmental noise. White-throated dippers, Cinclus cinclus, invariably nest over fast flowing water. Water stream noise can reach high sound pressure levels and exhibit a typical pink noise likely to constraint vocal signals. By monitoring a wild population, we first showed that pairs raised less fledglings in loud nest sites than in quieter areas. Secondly, we measured the impact of noise levels on vocal signals produced at the nest by using both a correlative approach (between-nest design) and an experimental approach amplifying the local environmental noise at the nest with a playback (within-nest design). Dippers vocalize at frequencies that do not overlap with the frequency range of the noise and the frequency composition of vocalizations did not change in response to the playback; suggesting that water stream noise has favoured the evolution of high frequency signals. Pairs breeding in louder sites vocalized at higher amplitude and increased the amplitude of their vocalizations in response to the playback; providing strong evidence of a Lombard effect. Pairs breeding in louder nest sites produced more pure tones-like vocalizations and showed vocal flexibility in response to the playback, using notes with a sharper and narrowed frequency spectrum. Our results show that low reproductive success in high environmental noise level may be explained by constraints on vocal communication.