Ardea
Official journal of the Netherlands Ornithologists' Union

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Rijnsdorp A.D. (1986) Winter ecology and food of Wigeon in inland pasture areas in The Netherlands. ARDEA 74 (2): 121-128
In 1979-80, the winter feeding ecology of Wigeon was studied in the Zaanstreek and surroundings (c. 500 km2), an inland pasture area situated in the south-eastern part of the Dutch province of Noord-Holland. The distribution of fresh droppings over the area revealed that pastures in the reclaimed polders were less intensively grazed than those in the peat-bog area and that birds show a strong preference for wet pastures with a short sward dominated by Alopecurus geniculatus, Agrostis stolonifera, and Poa spp. These grasses were the main food plants found in the fore guts of birds shot. Faecal analyses showed the same preference of Wigeon for these grasses. Selection experiments with caged birds revealed that Wigeon actively select these soft grasses. This preference can probably be explained by the better digestibility of soft grasses over coarser ones. The availability of surface water on the pastures also influences the grazing intensity on the parcels. Feeding birds loose 24 g of water per hour through the faeces. In order to get their feeding rate at the maximal capacity in the long term, they car .only compensate for such a high loss by regular drinking during feeding bouts. Grazing pressure amounted to 425 (intensively studied area) to 500 (entire study area) Wigeon-days ha- l winter-1. Grazing intensity on preferred pastures amounted to 673 Wigeon-days ha- l winter-1.


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