Ardea
Official journal of the Netherlands Ornithologists' Union

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Evans M.E. (1982) Movements of Bewick's Swans Cygnus columbianus bewickii marked at Slimbridge, England from 1960 to 1979. ARDEA 70 (1): 59-75
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Between 1960 and 1979, 962 different Bewick's Swans were caught at the Wildfowl Trust, Slimbridge, England, mainly in a channel leading from a lake. Most were ringed with engraved plastic rings, readable from 300 m. In six winters some swans were also dyed yellow on tail and wing tips. Away from Slimbridge swans were either identified as individuals (through ring number or bill pattern, which was different on each bird), or observed as Slimbridge-marked (with ring or dye) although not identified. One identification consisted of reports of a swan at a site on one or several dates. Sixty-two swans were identified in West Germany, The Netherlands, and Britain before arriving in the same winter at Slimbridge. Two birds were recorded at a site 160 km to the east and at Slimbridge on the same day. Two hundred and one swans were identified in these same countries between first arrival at and last departure from Slimbridge in the same winter. After departure from Slimbridge 458 swans were identified or recovered later in the same winter in Ireland, Britain, The Netherlands, West Germany, Denmark, East Germany, Estonia, U.S.S.R., while dyed swans were also seen in Poland and Sweden. One bird departing from Slimbridge was in West Germany on 1 January; another was recorded there one day after leaving Slimbridge. Swans marked at Slimbridge (n = 528) were identified in Ireland, Britain, The Netherlands, West Germany, Denmark and East Germany during winters when they did not visit Slimbridge, and 32 recovered. A ringed, but unidentified, bird was seen in the Shetland Islands; another in the south of France. Movements of swans between two sites, other than Slimbridge, highlighted the importance of West German sites in the spring. Families mostly stayed together on migration, but instances when they split up are detailed. A pair and their offspring, well documented in three winters, tended to use the same sites on migration each year. Timings of departure from Slimbridge were much earlier than those from sites as far west, possibly due to supplementary feeding under floodlights. The greater number of identifications in spring than in autumn, and in Britain, The Netherlands and West Germany, compared with the rest of the migratory route, are discussed. Other marking methods (neck collars, radio tracking) are examined. The public awareness value of marking birds is stressed.


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