Les bernaches hivernant dans le golfe du Morbihan (sud Bretagne) et leur impact sur les herbiers de Zostères : premiers résultats
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1987
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Roger A. Mahéo et al., « Les bernaches hivernant dans le golfe du Morbihan (sud Bretagne) et leur impact sur les herbiers de Zostères : premiers résultats », Revue d'Écologie (La Terre et La Vie) (documents), ID : 10.3406/revec.1987.6250
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The Golfe du Morbihan (11,500 ha) is characterized by extensive mixed sand and mud flats (61 %) ; the intertidal area approximates 4 300 ha. Seagrass beds (Zostera marina and Z. noltii) were covering approximately 1 900 ha during the 1978-1982 period. The biological cycle of the plants is unimodal throughout the year, with a maximum in summer (biomass : 100-120 g, dry weight, per m2 for Z. noltii, 110 g, dry weight, per m2 for Z. marina, typical form, and 240 g, dry weight per m2, for Z. marina, annual form). The Dark-bellied Brent Geese Branta b. bernicla visit the Golfe du Morbihan from October to April, with a peak in November (14,000 to 20,000 birds yearly during the past few years, representing 9 to 12 of the World population). The geese feed on Zostera which are grazed as soon as the grass becomes accessible at low tide. The use of exclosures allowed for an estimate of the quantity of food eaten by the birds : approximately 51.6 g, dry weight, per m2 during the winter.