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Bewick's and "Vhooper Swans Cygnus Columbianus Bewickii and C

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Bewick's and Bewick's and "Vhooper Swans Cygnus columbianus bewickii and C. cygnus: the 1994-95 season J. BOWLER,L. BUTLER,c. HESKETH,R. HESKETH,c. LIGGETTand E. REES The start of the 1994-95swan season at Washes with up to 905 birds on occasion Wildfowl & Wetlands Trust Centres was on the Welney refuge. later than normal because of the weath- The 1994-95 winter in Britain was er conditions in Iceland during October. exceptionally mild until early March, as A dominant southwesterly airflow with indeed it was throughout most of conti- associated heavy cloud-cover delayed nental Europe. Bewick's Swans conse- the departure of the bulk of the quently arrived both later and in small- Whooper Swans until a weather window er numbers than in recent years. The of clear skies and northerly winds on 26 first Bewick's Swans arrived on 17 and 27 October. The very first Whooper October at Welney, on 18 October at Swans appeared on 28 September at Martin Mere, on 19 October at both Caerlaverock and Martin Mere and Caerlaverock and on 20 October at on 4 October at Welney, but it was not Slimbridge. These were fairly typical until the end of October that numbers arrival dates but the subsequent rose to above 100 at any of the Wildfowl increase in numbers at all sites was slow & Wetlands Trust reserves. There were and peak counts during the winter were large influxes of Whooper Swans to the low. The maximum count of Bewick's British Isles in November and numbers Swans on the Ouse Washes at Welney continued to build up at Martin Mere was just 3,668 on 4 December, whilst and on the Ouse Washes at Welney peak counts of 548 at Martin Mere on 15 throughout November and December December and 286 in the Severn valley reaching record-breaking levels at both on 7 February were also disappointing. sites. A total of 738 Whooper Swans Larger numbers of Bewick's Swans than were present at Martin Mere on 13 normal (c.10,000) are known to have December which was a new reserve remained in The Netherlands this winter record, a further 35 birds were present (T. Haitjema pers. comm.) probably as a some 25 miles further north near Pilling result of the mild conditions. The mass on the Fylde bringing the Lancashire departure of Bewick's Swans from county record to at least 777 Whooper Britain was also earlier than normal. Swans. Not to be outdone, Welney Continuing mild weather with played host to 853 Whooper Swans on 4 favourable southwesterly 'tail-winds' December which with the 289 birds pre- encouraged the bulk of the Bewick's sent on the RSPBsection of the Washes, Swans to depart from the Ouse Washes produced a grand total of 1,142 and Martin Mere in early February, a full Whooper Swans for the whole of the two to three weeks earlier than usual. Ouse Washes, the largest single concen- The Bewick's Swans at Slimbridge lin- tration of the species ever recorded in gered a little longer but most had England. Whooper Swans have certainly departed by the end of February. benefitted from recent reserve manage- The proportion of Bewick's Swan ment at both Martin Mere and Welney; cygnets recorded at Welney and Martin around 700 Whooper Swans were to Mere indicated that 1994 was another remain at Martin Mere for much of the poor breeding season, with some 8-11% season, whilst over 1,000 Whooper juveniles in the population, well below Swans spent the winter on the Ouse the average of 15-16%cygnets recorded 176 Wildfowl 46 (1995): 176-187 Moulting Mute Swans 177 during the 1970s and 1980s. There have enth year she was accompanied by her now been four poor consecutive breed- second mate, Punter, with whom she ing seasons since the last above-average successfully raised two cygnets this sea- breeding season in 1990.As in the 1993- son. A fodder beet field, planted on the 94 winter, the proportion of cygnets at reserve specifically for the swans, Slimbridge was higher, however; 13.6% attracted the bulk of the birds through- of all Bewick's Swans recorded at the out November, whilst in December the site during the winter were juveniles, birds favoured a flooded pasture field suggesting a bias in the distribution of adjacent to the beet field and frequently family parties throughout the wintering commuted between the two fields dur- grounds. The Whooper Swans, on the ing the day. These two fields served to other hand, appeared to have had a hold the swans at Slimbridge and num- good breeding season in Iceland in 1994, bers were correspondingly low at with estimates on the wintering grounds Walmore Common, an important alter- ranging from 17%juveniles in the herds native feeding area lying some 10 km at Martin Mere and Welney, to 20.9% at north of Slimbridge, despite the pres- Caerlaverock. ence of extensive flood-w<;ltersat the site for much of the period. Only a hand- ful of birds were recorded feeding at Review of the season at WWT Centres Walmore Common before the New Year, with a peak of 23 on 18 December, and all returned to Slimbridge each evening Slim bridge to roost. A short period of freezing weather in The first Bewick's Swan to arrive at the New Year caused a small influx of Slimbridge was Auberon, who flew into swans, with numbers rising to 216 on 3 the European Pen early on the morning January. Numbers at Slimbridge then of 20 October, having first been seen on declined as birds began to make use of the River Severn at dawn. Auberon was flood waters at Walmore Common both also the first Bewick's Swan to arrive at for feeding and roosting purposes. A Slimbridge during the 1992-93 winter combined count on 10 January found a and is a regular member of the group of total of 244 swans divided between the swans that roost on pools in the collec- two sites of which 66 were at Walmore. tion area. The arrival date was roughly The Walmore flock decreased in mid- average for Slimbridge, but the swan January, however, and numbers corre- departed the next day and it was not spondingly increased at Slimbridge; a until 4 November that the next seven total of 253 was counted at Slimbridge birds appeared. The build-up in swan on 15 January and some 130-150swans numbers was relatively slow with roosted each night on Swan Lake for counts rising from 48 on 6 November, to most of the month. Numbers declined at 63 on 21 November and to 120 on 28 the end of the month, to around 160, as November. Amongst these arrivals were swans returned to Walmore in order to Pedro and Weaver with four cygnets, take advantage of extensive flooding on returning for their second consecutive the common, following a period of winter at the site. Pedro now appears to unusually heavy rainfall. A count of 127 have forsaken Welney after ten years at Bewick's Swans at Walmore Common on the site in favour of Slimbridge, which is 24 January was the highest of the winter the traditional wintering site of his mate for this important alternative site. A few Weaver. new swans appeared at Slimbridge dur- Swans continued to arrive almost ing the first week of February and a daily in small groups throughout simultaneous count of Walmore and December with numbers rising to 140on Slimbridge on 7 February found a total 5 December and to 182 on 29 December. of 286 swans in the area of which 188 Amongst the December arrivals was were at Slimbridge. This was the highest Casino. Now in her twenty-fourth year, count of the winter for the Severn valley Casino was the oldest surviving flock. Around 90 to 100 birds remained Bewick's Swan to return to Slimbridge at Walmore until 9 February when the during the 1994-95 winter. For the sev- floods receded rapidly, encouraging the 178 Moulting Mute Swans swans to leave the site. Not all of these tissues for lead shot; 33.3% of the adult birds returned to Slimbridge, however. swans were found to be carrying gun- Sightings of ringed birds revealed that shot in their tissues, a very similar fig- some, at least, moved north along the ure to previous estimates. None of the River Severn to make use of flooded pas- cygnets were found to be carrying shot ture in the Ashleworth and Coombe Hill however which suggests that the illegal areas. Over 100 Bewick's Swans were shooting of Bewick's Swans may be present on the floods near Coombe Hill more common in the spring. on 19 February whilst some 60 to 80 of Swans that had been ringed else- these birds moved on to frequent the where, but which were identified at Ashleworth area until the second week Slimbridge during the course of the win- of March. ter included Pedro from Welney, four Some 200 Bewick's Swans were pre- birds originally marked at Martin Mere, sent at Slimbridge in mid-February but and four birds that had been fitted with the mild conditions and persistent neck-collars in Russia. These included south-westerly "tail-winds" resulted in two birds (148P and 409P) which visited the birds leaving the site towards the Slimbridge during the 1993-94 winter end of the month. The first large depar- and another (430P) which had been ture occurred just after the second seen at a nearby site along the River afternoon feed at 1700 hrs on 26 Wye at Letton, Herefordshire, also in February when a group of 75 swans 1993-94.
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