Swans are a beautiful sight along our river at this time of year – but don’t get too close! Michael Krause from the Great Ouse Valley Trust explains why.

Mute Swans – white, large, orange beak, long, curved neck – are with us all year round. They look stately, elegant, and calm.

But now their behaviour changes, and maybe that changes our view of them. Some people even call them aggressive. Observing them in spring and summer helps us understand this change.

Spring is the breeding season. Swans are thought of as faithful and monogamous, pairing for life. That’s not quite true.

The strong pair bond does lead to long relationships, but breeding failure could lead to a split.

Most pairs will be mating again, as they have done for perhaps many years, and could well be using the same nest as last year.

The female, called a cob, will sit on a large mound of vegetation in shallow water on an island or the riverbank.

The majority of the UK’s 5,000 pairs need a ‘territory’ – their own patch with space to nest, and sufficient food for the family, without other swans around.

The parents’ job is to raise young - and that’s not an easy task. The cob lays four to seven eggs, each weighing more than a pack of butter, and incubates them for around 40 days.

Once the cygnets hatch, it will be four months before they can fly. They depend on the parents to protect them, and swans do that bravely.

What you think is aggression, if you get too close, is in fact a defence mechanism. When the neck curves back and the wings rise up, the swan wants to chase you away as a threat.

It needs to put up a strong defence of the nest, its mate and its young. A loud hiss says, ‘back off’.

And backing off is a good move. You may have heard that a swan’s wing can break your arm. But birds have light bones to make flying easier – and so the story is a myth. Swans will, however, fight off foxes, birds of prey and other predators.

Defending nests and chasing predators away from their chicks is instinctive to many bird species. Rarely is this behaviour as visible to us as it is with swans.

It’s a real insight into the trials of life so many animals face. Enjoy your local swans. Do keep your distance (and your dog on a lead), so the swans can concentrate on looking after their cygnets.

For more information about the Trust visit: www.greatousevalleytrust.org.uk