Land-use changes and the resulting habitat degradation have been regarded as the most important known causes of waterfowl population declines. We assessed the habitat requirements of waterbirds, including waterfowl, in a hemiboreal, agricultural watershed in southern Finland. We related the birds' species diversity, abundance and brood numbers on ten lakes to environmental variables, including land use characteristics as well as topographic and local biotic features. Both species diversity and pair numbers responded to land use characteristics, such as the area of agricultural land surrounding the lakes. Our results suggest that land use may reflect habitat quality, possibly in terms of resource availability and predation risk. The pair numbers of waterbirds grew along with the availability of invertebrates, an important food resource. The abundance of gulls affected the diversity, abundance and reproductive success of waterfowl positively in our study area, probably because they provided shelter from predators.