An invasive alien bivalve apparently provides a novel food source for moulting and wintering benthic feeding sea ducks

Since its introduction from North America in the 1970s, the American razor clam Ensis leei (M. Huber, 2015) has successfully spread throughout North Sea coasts from Spain to Norway and the United Kingdom to the western Baltic. We investigated the distribution and abundance of this non-indigenous bivalve species as a potential novel food resource for common scoter Melanitta nigra (Linnaeus, 1758) along the eastern German North Sea coast. Highest densities of flightless moulting and wintering common scoters coincided with areas of high E. leei abundance. Other European studies showed common scoters extensively feed on E. leei. Even with these findings, it remains difficult to demonstrate convincingly that E. leei constitutes a major food source for common scoter in the German North Sea during their non-breeding season. However, our study suggests that E. leei has become an important prey item for internationally important concentrations of common scoters at large spatial scales.