Eider sisterhood
Female Eiders pull together and are quite remarkable when it comes to bringing up the young – but this colony sisterhood is not free from abuse
Female Eiders really pull together in a colony, explains Dominic Couzens
IN 2014, A Midlands’ art gallery caused a rumpus by unveiling a life-sized bronze statue called A Real Birmingham Family outside the city library. Costing a small fortune of public money, it caused controversy by depicting nothing more than two single mothers with their young children, and not a man in sight. Bearing in mind that it was meant to depict ‘the most real’ family in the city, that seems something of an oversight, since there are plenty of fathers in Birmingham. I know, I’ve been there. There is, however, an entirely appropriate place to put this statue – indeed, multiple places.
These are fortresses where families are truly bastions of feminine exclusivity, power and togetherness, where males really are relegated almost to a place of sperm-providers, separated from the upbringing of their children. Let me introduce you to colonies of Britain’s most sociable duck, the Eider. This heavy-bodied sea-duck is found around the rockier coasts of Britain, where it feeds on mussels and other shellfish, prizing them off rocks underwater. In the breeding season, it retreats to nearby low-lying islands cut off from the land, and hence ground-predators; but farther north, in the Arctic, for instance, it may settle on mainland peninsulas and coastlines. It nests on the ground. Eiders most typically breed in colonies, and these are sometimes huge. There may be a few tens scattered about, but in parts of the range, such as Iceland, there may be 10,000 to 15,000 nests at high density. If you bear in mind that the male Eiders invariably exit stage left soon after the last eggs are laid, that sets the scene for what must be some of the largest gatherings of adult female birds in the world (this is unusual, because in most bird colonies, including gulls, auks and cormorants, the males bring food to the females and to the developing young). For the next three months – about 26 days to hatching, then 55 more days to independence – the youngsters are immersed in an all-female environment. It isn’t only mothers. Many young females, less than four years old, will spend substantial time in the colony and some will help with chores later in the breeding cycle. Eiders are famous for their nests. In structural terms, these are nothing special, just
There is a ‘Cuckoo’ in the nest. And what she does is similar to that of the famous brood parasite
a depression on the ground, often among vegetation offering a degree of shelter. It is the components that are extraordinary, the ‘eider down’ that lines the nest and may cover the eggs. This is indeed down plucked from the mother’s breast, ready-made nest material of exceptional softness and cohesiveness. In the Arctic conditions into which many an Eider egg is laid, the down helps to insulate against the cold. The down has been harvested by people since the Middle Ages, and probably well before. A very small, albeit lucrative industry, still exists in Iceland, exporting Eider down for the luxury market in duvets, sleeping bags and clothing. The down is apparently unusually light and, unlike synthetic materials and goose down, it doesn’t so easily fall apart. Apparently, a sleeping bag with true eider down filling keeps you warm when it is -35°C outside, while synthetic fills protect you down to -7°C. The birds in the harvested colonies are looked after well by the operators, who protect the nests from gulls and other potential predators. In turn, the incubating birds are typically tame, even allowing people to stroke them as they incubate. The Eider’s dedication to its incubation is also rightly celebrated. These birds sit tight on their clutch of between three and five eggs, to the extent that they barely even leave them alone, even only for a moment. In colonies that regularly suffer disturbance, they sometimes don’t move at all after the first week of incubation. They don’t feed, living instead off accumulated fat. They cannot easily drink, although they do sometimes sip from a small puddle of rain water that might accumulate in a depression in the feathers of their dorsal area – adding a new dimension to the phrase ‘water off a duck’s back’. Incubating females have been known to lose
The extraordinary advantages that female Eiders confer upon their eggs – being cosily wrapped in the world’s best insulator, under one of the world’s best incubators
45% of their initial body mass while discharging their duties. The extraordinary advantages that female Eiders confer upon their eggs – being cosily wrapped in the world’s best insulator, under one of the world’s best incubators – don’t extend far beyond the point of hatching. Young Eiders enter the outside world well developed, and almost immediately can walk about, swim and dive under their own steam. But while they leave the warm physical embrace of their mother’s body, they enter into a different kind of embrace – that of the colony sisterhood. These Eider colonies are highly unusual for their benevolence. In a gull colony, a peripatetic individual wandering away from its parents’ territory might well be attacked and even killed. There is no prospect of that here. A youngster is born into the care of Eider Social Services. Even during the hatching process, a mother Eider might find herself surrounded by an admiring coalition of interested females. These are typically adults that have failed to breed at all or have, perhaps because of poor body condition, had to abandon their clutches. These birds join the mother in accompanying the chicks to water, and will take part in their subsequent protection by making threat displays towards potential predators. They are often known as ‘aunts’, and there is evidence that some at least might be related to the mother. Even where there are no aunts present, Eider families coalesce easily, and several may join together on the walk to water, to such an extent that the broods become fundamentally mixed up. Within a few days crèches form, usually with 20-30 chicks in each one. Oddly, an attack by a predator is often the trigger for crèche-formation. The young bunch together for protection and, even more oddly, may then stay together until they are independent. The crisis leads to several weeks of mingling. Brood-mixing of a kind does seem to
SEA DUCKS
Eiders are birds of the coast and sea, diving to the seabed to collect shelled molluscs be a theme with Eiders. It is not at all unusual for chicks to be adopted into different families, even where crèches don’t form. And even eggs are a currency for co-operation.
Female Eiders sometimes ‘dump’ additional eggs in a nest and, remarkably, another female will sometimes incubate these successfully, adopting them as its own. The birds concerned might be inexperienced individuals wishing to ‘practise’. However, before you whoop too quickly at the triumph of seaduck feminism, you should be aware that Eider co-operation is not entirely free from abuse. There is a Cuckoo in the nest, the rogue female. And what she does is, indeed, similar to that of the famous brood parasite. Some individuals attempt to increase their productivity by laying eggs in the nest of another bird, in addition to eggs that they lay in their own nest. In other words, they subcontract some of their incubation duties on to the burden of a different individual. When you bear in mind the exceptional efforts Eiders make to look after their eggs, it certainly looks like a dirty trick to pull. Brood parasitism by Eiders tarnishes the apparent feminine idyll within the colonies, but one thing it does prove. There is nothing average, and nothing ordinary, about the breeding of these remarkable birds.