An army of counters has just visited all known haunts of migrant swans in Ireland. The surveyors were are participating in the International Swan Census, held every five years.
We have three swan species here. The ‘mute’, the one everybody knows, is an all-year-round resident. It has a curvaceous Celtic-art-style profile and an orange bill topped by a black nose-like ‘berry’. Although it can snort grunt and hiss, this swan is ‘mute’ compared to its migrant cousin, the whooper, which honks loudly.
Few people encounter this winter visitor from Iceland. It has an angular shape, with a long straight neck held vertically upwards, topped by a ‘triangular’ head. The bill is yellow and black with no ‘berry’.
Mutes will live close to people, even in cities, availing of hand-outs of bread. Whoopers are shy and keep their distance.
This behaviour is somewhat counter-intuitive; birds living in remote northern locations encounter few people, so they tend not to fear humans. Mute swans, on the other hand, run the gauntlet of vandals dogs and disturbance, especially when nesting. Knowing from bitter experience how destructive we can be, you would expect them to be the wary ones.
The opposite, however, is the case. The third Irish swan species, the Bewick, arrives from Arctic Russia each autumn and departs in spring.
Resembling a smallish whooper, it wasn’t recognised as a separate species until 1830, when it was named after Thomas Bewick, author of a celebrated two-volume History of British Birds.
Its bill is black and yellow but, whereas yellow predominates on the whooper’s, the Bewick’s bill is mostly black. The international survey covers only the migrant species. Oddly, these are easier to census than the sedentary mutes; they gather in flocks at fairly traditional locations where it’s not too difficult to count them.
Some mutes visit ‘herd’ locations but many remain at their breeding haunts for the winter. Finding and counting these dispersed individuals, and their mature cygnets, would be a time-consuming hit-and-miss affair.
Swans appear rather set in their ways, so you might expect little change to occur from one census to the next. However, things are far from static in the swan world. The fortunes of Bewicks, in particular, have changed dramatically.
“We owe to Thompson the discovery that the Bewick is the swan which visits Ireland in the greatest numbers” wrote Richard Ussher and Thomas Warren in 1900.
This Siberian breeder was our dominant migrant swan back then.
Fifty years later, however, the whooper had overtaken it. The late Oscar Merne estimated that about 2,500 Bewicks spent the winter here in the early 1950s. Numbers at their main haunt, the Wexford slobs, reached 700. Then decline set in; by 2005 there were fewer than 300 in the entire country.
Does this mean that the Bewick is in trouble? Not necessarily. With global warming, migrants may find suitable wintering locations closer to their breeding areas and avoid the onerous and dangerous journey to Ireland.
Will the 2020 census reveal that our Bewick numbers are down to double figures? As climate change proceeds, are more whoopers choosing to stay on in Iceland, not bothering to come here?
Is it, too, destined to become a scarce visitor? The census results won’t provide all the answers but they may reveal trends.