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Die Quantitative Bedeutung der Wasservögel für das Ökosystem eines Innstausees

  • J. Reichholf

Abstract

The impoundments of the lower Inn river on the border of Lower Bavaria and Upper Austria belong to the most important wetlands in Central Europe. More than one fourth of the total of waterfowl and waders which are counted at the international wildfowl census in Bavaria or Austria may be found on these reservoirs, which are of comparable small size (some 10 km2 each of the four reservoirs). Maximal concentrations may exceed 50 000 individuals of ducks, coots, gulls, and waders.

The ecological effects of these concentrations of birds were investigated during a three years period of study from 1971 to 1973. The available food resources for the water bird community were measured by means of quantitative sampling of the muddwelling fauna and the standing crop of submerged vascular plants. The seasonal distribution of the standing crop of biomass production usable for aquatic birds is shown in fig. 1. The total amount of biomass produced during the summer months exceeded 2,9.106 kg of muddwelling fauna and 0,6.106 kg of aquatic plants. These values indicate the highest level which is reached normally in August. The water bird community uses this amount during autumn with an efficiency of 15 to 90% of the available organic material from the first and the second trophic level. The difference is caused by the hunting pressure mainly. The protected regions of the reservoirs show the high percen-tages (90% or so) according to the concentration of ducks, coots, and swans in the undisturbed regions.

The two main food chains have considerable lag-phases in the seasonal pattern (fig.2). Input of nutrients, production and consumption are well separated in the course of the year. Thus the high percetages of the consumption of the produced biomass are possible.

It may be concluded that the water bird community is of central importance for the biolo-gical energy flow in the ecosystem of the reservoirs of the lower Inn river.

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Literatur

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Copyright information

© Springer Science+Business Media Dordrecht 1976

Authors and Affiliations

  • J. Reichholf
    • 1
  1. 1.Zoologische StaatssammlungD-8 München 19Deutschland

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