The mystery of a swan's death in County Offaly

The commonest cause of death in mute swans is collision with cables when flying.  A swan’s eyes, located at the sides of the head, give it virtual all-round vision, warning it of impending attack by predators. But it can’t see well in front of it and may not notice a cable until it’s too late to avoid a collision

A mute swan and her five cygnets search for food the in the shallow stream at Marina Park, Ballintemple, Cork in bright sunshine. File picture: Larry Cummins

… one of the simplest things of all, and the most fundamental, is violent death — Ernest Hemmingway. Death in the Afternoon

A swan was found dead at Connolly Park, a residential area of Tullamore, on April 7. County Council staff removed the carcass. According to Ger Scully of the Offaly Express, the Forest and Wildlife Service is investigating.

A photograph in the Express shows the bird lying face down on grass. A black cat is crouching nearby. The deaths of Hemmingway’s bull-fighters may be ‘one of the simplest things’, but discovering why a swan died in such an unlikely location isn’t simple. The cat is perplexed. So am I.

We used have three species of swan in Ireland, but one of them, the Bewick’s, hardly visits us nowadays. Bewick’s breed in Siberia and had south, seeking milder conditions, for the winter. Around 2,000 of them visited us annually from October to March. Then global warming rendered locations closer to home viable as wintering haunts; the migrants no longer need to travel as far as Ireland.

Our other winter-visiting swan, the Whooper, still comes to us from Iceland. The familiar mute swan is resident here all year round.

A mute swan puts on a display, as kayakers make their way to Innisfallen Island from Ross Castle, Lough Lein, Killarney National Park, as part of the Wander Wild Festival in Killarney. Picture: Valerie O’Sullivan

The victim in Offaly isn’t a whooper or Bewick’s; it’s a mute. The mantle and rump, normally hidden under the folded wings, are exposed. Tell-tale brown smudges, found on the back feathers of young adult swans, are absent. This bird, therefore, was at least two years old.

Between 1983 and mid-1994, I ringed 1,315 mute swans, of which 292 were found dead subsequently. The cause of death was determined in 156 cases. Six birds had been shot. Five were attacked by dogs or foxes. There were five cases of vandalism and four road casualties. Lead and warfarin poisoning accounted for 11 casualties. Contamination from oil spillages claimed 17 victims.

All of these causes of death can be ruled out in the Tullamore case. Poisoning, would hardly explain this death. Swans don’t land on green spaces of housing estates and then die. A sick or poisoned swan wouldn’t even be able to travel.

The commonest cause of death in mute swans is collision with cables when flying. It accounted for at least 95 deaths in Dublin and Wicklow.

A swan’s eyes, located at the sides of the head, give it virtual all-round vision, warning it of impending attack by predators. But this comes at a price — the bird has limited forward vision — it can’t see well in front of it. Heavy and lumbering in flight, it may not notice a cable until it’s too late to avoid a collision.

Swans seldom fly across open country; they prefer to follow rivers or canals, with the occasional short cut to avoid a river bend.

However, the Grand Canal, at Tullamore, is straight. A swan is unlikely to divert over Connolly Park. And what obstacle might it have struck had it done so? Chimneys nowadays are no longer adorned with television aerials.

A child’s bike appears in the Express photo. Could children have found the carcase close to the canal and dragged it towards home?