Birds in the trophic web of Lake Esrom,Denmark

Using an extended method for calculating food consumption by diversified bird communities taking into account variability of diet, energy content and digestibility of different food items within a diet, it was possible to calculate the energy consumption of the bird community in eutrophic Lake Esrom. As the production of food items and energy flow in Lake Esrom have been well studied, it was possible to relate the bird community to the trophic web. Birds consumed approximately 20% of the annual macrophyte production (excluding roots and rhizomes), and 4% of the annual zoobenthos production. The annual consumption of fish by birds corresponded to 22% of the annual consumption by piscivorous fish measured in kJ, and was almost the same as the commercial fishery catch. However, the consumption of fish by birds consisted mainly of non-piscivorous fish, in contrast to the commercial catch. In Lake Esrom, the birds have a significant role in the energy flow of consumers within the ecosystem. This result indicates that bird communities should be included in future studies of lake ecology. Also, competition between fish and birds is potentially significant.