Response of herbivorous water-birds to the return of Chara in Lake Veluwemeer,The Netherlands |
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| Institution: | 1. Departamento de Ciencias de la Tierra, Universidad de Zaragoza, C/Pedro Cerbuna 12, 50009 Zaragoza, Spain;2. Instituto Geológico y Minero de España, C/Ríos Rosas 23, 28003 Madrid, Spain;3. Departamento de Geodinámica, Universidad de Granada, 18071 Granada, Spain;4. Departamento de Geología y Geoquímica, Universidad Autónoma de Madrid, Campus de Cantoblanco C/Fco, Tomás y Valiente 7, 28049 Madrid, Spain;5. ESGEMAR, Espacio 4, Polígono San Luís, 29006 Málaga, Spain;1. College of Life Sciences, Jiangxi Normal University, Nanchang 330022, China;2. Key Laboratory of Forest Ecology and Environment of State Forestry Administration Institute of Forestry Ecology, Environment and Protection, CAF, Beijing 100091, China;3. Nelson Institute for Environmental Studies, University of Wisconsin-Madison, 550 N. Park St., Madison, WI 53706, USA;1. Centre for Genetic Disorders, Faculty of Science, Banaras Hindu University, Varanasi, India;2. Swami Harshankranand Ji Hospital & Research Center, Varanasi, India;3. G S Memorial Plastic Surgery Hospital & Trauma Center, Varanasi, India;4. Department of Obstetrics & Gynaecology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India;5. Department of Plastic Surgery, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India;6. Centre for Genetic Disorders, Faculty of Science, Banaras Hindu University, Varanasi 221005, U.P., India |
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| Abstract: | Water-birds were almost absent from Lake Veluwemeer during the 1970s and 1980s, due to low food availability related to eutrophication. Several restoration measures have resulted in the recolonization of the lake by Chara spp. during the 1990s. Bird numbers in autumn and winter have increased along with charophyte biomass. Linear regression analysis was used to relate bird numbers to the abundance of their potential food sources Chara, pondweeds, filamentous macro-algae (FA) and zebra mussels (Dreissena polymorpha) within the depth range available to each species. Numbers of mute swan (Cygnus olor), pochard (Aythya ferina), tufted duck (A. fuligula), coot (Fulica atra) (R2≥0.98), gadwall (Anas strepera) (R2=0.78), Bewick’s swan (Cygnus columbianus) (R2=0.79), red-crested pochard (Netta rufina) (R2=0.76) and pintail (Anas acuta) (R2=0.38) showed significant correlations with these food sources. Chara biomass explained most of the variance in all species except for gadwall. Both bird numbers and their duration of stay were closely associated with the presence of Chara. Grazing pressure was low during spring and summer and Chara colonized the lake in spite of consumption. It is argued that birds did not slow down colonization of the lake by Chara during the 1990s, but may have accelerated succession from pondweeds Potamogeton spp. to charophytes. As more birds foraged on Chara compared to any other food resource, the preservation of large areas of Chara is of great importance to the water-bird community in Lake Veluwemeer. |
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