Are all swans birds of a feather? Afraid not

AT this time of year, swans get involved in fights. Worse still, young swans can be attacked by their fathers.

A distressed caller wanted me to restore order on a local pond, in a UN-style peace-keeping mission, and send the offending daddy for trial to The Hague. Such intervention, alas, isn’t on. An injured bird can be taken into custody for veterinary treatment. Otherwise capturing mute swans, a protected species, is forbidden by the 1976 Wildlife Act. But why do swans fight? These big vegetarian birds start laying from mid March. There can be up to nine eggs in a nest but the average is seven. I once saw 12. When the clutch is completed the female, known as the ‘pen’, sits for about 36 days, eating almost nothing. Her mate, the ‘cob’, patrols the territory, keeping other swans out and threatening any animal or person approaching the nest.

Swans make excellent parents, chaperoning their cygnets attentively. It will be late autumn before the young can fly. They don’t leave the territory immediately, but linger on at home. So much aquatic vegetation is eaten that only a well endowed location can support a family through the winter. On territories where food becomes scarce, parents and young fly together to the nearest swan-flock, known as a ‘herd’.

Paradoxically, cygnets from affluent territories face a major ordeal. Their parents won’t leave the territory lest it be taken by another pair in their absence, so the youngsters must find their own way to a flock. Children used to ‘move out’ in their late teens or early twenties but, nowadays, many continue living with their anxious parents into their 30s. Cygnets, likewise, don’t want to leave home where they have it so good. As spring approaches, the cob has a problem; the youngsters, now fully grown, are ‘eating him out of house and home’. His pen needs extra food to form eggs and lay on the fat she will need when incubating. In any case, the territory won’t support a new brood and last year’s one as well.

Nature takes a helping hand; the youngsters are replacing their brown cygnet feathers with white adult ones. By February, cygnets are more white than brown. Human fathers may take exception to the outlandish attire of their teenage offspring. A cob has a similar disposition. To him, white birds on the territory are ‘a red rag to a bull’. Even though they are ‘his own flesh and blood’, he turns on his offspring and drives them out. There can be mayhem and, occasionally, serious injury.

Pity the unfortunate youngsters. Never having been away from home, they are now all alone in a hostile world. Flying along rivers, harassed and moved on by the resident swans wherever they land, they are lucky to stumble on a herd. Colliding with overhead cables and unable to feed adequately, the death rate among young swans, at this stage of their lives, is huge. Of 258 three-month old cygnets, ringed by me on their natal territories around Dublin, only 138 (53%) could be found in herds the following spring.

Young swans spend years in these ballrooms of romance before securing a mate. In Dublin, 35% had partners by the age of three and 77% when they were five. The nuptials completed, the pair leaves the herd to search for a territory. Finding one is difficult. Most of the better locations will be occupied by older swans and competition can be fierce for the remaining ones. Disputes lead to fights. Cobs display at each other, puffing out their feathers, to look as big and powerful as possible. If an opponent is clearly larger, a cob will retreat but when the two are evenly matched, war may be declared. It can be a ‘life or death’ encounter. In the Dublin study, about 4% of recorded swan deaths were due to fights.

We may want to rescue vulnerable cygnets or defeated contenders but swans’ ways are not our ways and we mustn’t interfere in their lives.