There has been concern for some years that the smallest and rarest of the three swan species found in Britain, the Bewick’s swan, is disappearing from our shores. Its winter stronghold used to be in the south-west, especially the Severn estuary.
While the reduction in numbers appears alarming it may not mean the species is in danger. Researchers in the Netherlands, equally concerned about the decline in overwintering birds in their country, have discovered the swans have simply moved north. They have found that milder winters due to the climate crisis mean they do not have to fly so far south-west from their breeding grounds in northern Russia to find comfortable winter quarters.
Using GPS data it was even possible to show that Bewick’s swans overwintered 120km (75 miles) closer to their summer nesting grounds when the winter temperatures averaged 1C warmer and double that when it increased by 2C. Most of the population now overwinters in northern Germany.
Monitoring the behaviour of individual birds led to the conclusion that adults tended to stick to their old habits, using the same nest sites and overwintering grounds. It is the new generation, the juvenile birds that are migrating shorter distances, gradually causing a territorial shift of the entire species.
