Miracle of the warm eider duck

THERE’S an interesting paper on eider ducks in the current edition of Irish Birds.

The eider is a bird with ‘profile’, both ancient and modern. St. Cuthbert, the 7th Century hermit and bishop of Lindisfarne, had a special relationship with the bird; they are still called the Cuddy ducks in Northumberland.

Eiders were so devoted to the holy man that they followed him around. The more gullible members of his congregation thought that this was miraculous, but there’s a more mundane explanation. Ducklings, just out of the eggs, will follow the largest object moving in their vicinity and become ‘imprinted’ on it for life. This is normally the mother duck. Cuthbert must have raised ducklings in captivity.

Nowadays, the eider is famous for another miracle; the extraordinary warmth of its down. This sea-duck of sub-arctic waters must be able to stay warm in all weathers. To do so, it developed a thick coat of body feathers. ‘Eider-downs’ were in vogue when I was a child. The feathers, in the ones we had, probably came from humble farmyard geese; the down of the legendary duck is a very expensive commodity. Other marine birds have equally good insulation, but the eider’s nesting habits enable the down to harvested easily and without harming the birds. Icelandic farmers encourage eiders onto their lands by persecuting the local Arctic foxes and scavenging gulls. The ducks soon learn that ‘eider farms’, marked with colourful streamers blowing from poles in the wind, are safe places to nest. They repay the farmer with the down they use to insulate and cover their eggs. This is gathered when a bird leaves the nest. A farm I visited some years ago had almost 2,000 eiders in residence on a few hectares of rocky ground.

These ducks breed extensively along the northern coasts of Ireland. This wasn’t always the case. Richard Ussher and Robert Warren, writing in 1900, claimed that the bird was ‘a rare straggler’. The first Irish nest was found in 1939. Forty years later, there about at least 100 between Sligo and Down. The bird’s range is still increasing; breeding was recorded recently in Mayo and on an island off the Dublin coast. Our breeding eiders are sedentary, staying in the same general areas throughout the year. They are joined in autumn by foreign birds. Pairs form in winter. Remote locations, preferably on islands, are chosen for the nests. Safety from predators, such as foxes and mink, is paramount.

In April 2009, Kerry Leonard of Bangor counted the eider ducks on the coasts of Derry Antrim and Down. His findings appear in the current edition of Irish Birds. Females, sitting camouflaged on their eggs, are difficult to spot and almost impossible to count. A 15-day period in early to mid-April was chosen for the survey; the foreign birds would be gone by then and local females would have moved to their breeding locations but not yet incubating. A boat covered areas not accessible from land.

A total of 2,778 eiders was recorded, ten times the number found in a similar survey in 1977. There were 1,638 adult males, 45 immature males and 1,095 females. The 60:40 ratio of males to females seems odd; one would expect the numbers of males and females to be roughly the same. Were some females already on eggs and not counted? Nor can the number of nests be easily inferred from the female totals; immature females can’t be recognised in the field. Taking the various factors into account, he estimates that were about 1,050 nests. Some 78% of the birds were concentrated in Rathlin Island, Strangford and the Copelands off Belfast Lough. Large stretches of coast had no birds at all.

With the onset of global warming, you would expect eiders to retreat northwards but the reverse seems to be happening.

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