The influence of birds on the structure and functioning of coastal food webs


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sabine.horn [ at ] awi.de

Abstract

The Wadden Sea is one of the most important stop-over sites for migrating and breeding birds. About 10-12 million birds per year use the area for foraging and consume about 25 to 45% of the standing stock of macrozoobenthos. But little is known about the influence of birds on the entire ecosystem. We conducted Ecological Network Analysis (ENA) in an important breeding and resting site in the north-eastern German Wadden Sea to determine the influence of birds on the food web. The model was based on the yearly average of empirical data taken in the study site. In its current condition, the system appears to be in a well-balanced status, with a relative Ascendency of 32.3% and a robustness of 36.5%. The diversity of flows was high showed by a Flow Diversity of 5.1 and numerous parallel pathways represented by an Effective Link-Density of 3.3. A large variety of different bird species uses the area for foraging. As top predators, these bird species are included directly or indirectly in most of the pathways. Birds induce a huge negative impact on their prey items with a less pronounced positive feedback reaction to the competitors and food resources of those organisms. There is also a strong negative impact among the bird compartments probably due to competition between the bird species on the intertidal flats. Changes in the biomass of the birds revealed alterations in the food web structure. With a decline in the avian biomass the system showed a decrease in connectivity and diversity of flows but an increase in recycling. Birds therefore appear to be an important factor for the food web structure. Changes in the bird population could affect the complexity and functioning of the entire ecosystem. Thus, it is recommended to include birds in coastal food web studies which has rarely been done before. The use of such holistic approaches would facilitate undertaking management measures.



Item Type
Conference (Talk)
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Peer revision
Not peer-reviewed
Publication Status
Published
Event Details
ECSA 2017, "Where Land Meets Ocean: The Vulnerable Interface", 16 Oct 2017 - 20 Oct 2017, Shanghai.
Eprint ID
45784
Cite as
Horn, S. , de la Vega, C. , Asmus, R. and Asmus, H. , Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung (2017): The influence of birds on the structure and functioning of coastal food webs , ECSA 2017, "Where Land Meets Ocean: The Vulnerable Interface", Shanghai, 16 October 2017 - 20 October 2017 .


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