Low tide distribution of wintering waders and shelduck on the Severn Estuary in relation to the proposed tidal barrage |
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Authors: | NIGEL A CLARK ROBERT P PRYS-JONES |
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Institution: | British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU;Bird Group, The Natural History Museum, Akeman Street, Tring, Herts, HP23 6AP |
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Abstract: | Waders and shelduck were counted at low tide on 162 sectors comprising 85% of the intertidal area (21 467 ha) of the Severn Estuary on 12 occasions during winter 1987/88. On average, 50% of birds present at low tide utilized just 13 sectors (12% of the area); 90% of birds occurred on only 56 sectors, leaving large expanses of intertidal sand virtually devoid of birdlife. Dunlin, the numerically dominant species, occurred widely on the middle and outer estuary, whereas shelduck predominantly occurred on the outer estuary and redshank around many tributary river mouths. Curlew, the most ubiquitous species, was the only one concentrated on the inner estuary. Severe gales in both late December and mid-January concentrated all main species within fewer sectors, probably by the short-term removal of surface sediment from substantial areas. It is estimated that the proposed tidal barrage would eliminate intertidal areas accounting for between c. 40% (for shelduck and curlew) and 80% (for redshank) of current total low tide usage by the internationally important populations present. |
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Keywords: | intertidal birds feeding distribution sediment mobility |
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