Swan fall for Christmas!
Freezing temperatures, north-easterly winds and clear skies over Christmas have encouraged hundreds of Bewick’s swans on the continent to continue with their journey and finally reach Britain. Since Christmas Day, 81 swans have flown into Slimbridge, completing their 1,500 mile migration from the Russian arctic. This is a significant ‘swanfall’ and it was fantastic to see the Rushy brimming with 155 swans this morning, creating our very own white Christmas of sorts! Although day length dictates the broad migratory period, weather conditions, particularly wind direction, temperature and visibility, influence the precise timing of movements.
It’s been a long-awaited arrival. In the run-up to the festive period, we recorded half the number of swans we would usually expect at Slimbridge. The mild weather and southerly winds that characterised the first half of the winter meant that migration simply ground to a halt. Hundreds of swans remained in Estonia in the first week of December, a time when the country would typically be in the midst of a winter freeze and unable to support large numbers. So the Bewick’s remained east while we waited for them in the west!
The new arrivals at Slimbridge include six families and a Slimbridge regular called Aoki who flew in 47 days after his mate Lucius! Aoki and Lucius have been wintering at Slimbridge together since 2008. Given that Bewick’s swans have very strong loyalties to their partners, often mating for life, we feared the worst when Lucius arrived on his own in November. It is likely that they became separated during migration, perhaps after being disturbed, or during poor weather. Several years ago, Lucius fathered Crinkly with his previous mate Coletta. Crinkly beat the odds to return to Slimbridge five times despite having a deformity in her neck making her quite un-aerodynamic.
Many groups of Bewick’s have also been arriving at Welney and the Ouse Washes in Norfolk, a site of international importance for this swan population, attracting up to 4,000 birds in mid-winter. The cold weather has also prompted our transmitter swans to push onwards and we were delighted to see Lech arrive on the Ouse Washes this week, joining Andres who arrived in November! Hope has now flown from southern Denmark and is now just a short flight away in the Netherlands while Eileen is at Filso Fjord in Denmark, feeding in fields near Overup during the day. More news to follow.....
So far this winter, we have recorded 174 individuals at Slimbridge. Although similar to numbers recorded by the end of 2013, this still falls short of the average number of birds recorded by this time over the last 10 years (250 birds). An international swan census, co-ordinated by WWT and Dutch colleagues, will be held in January and will help to determine whether the population as a whole has continued to decline since the last census in 2010.
