The symbiotic duck

I learnt about this last year, and as an environmental scientist I thought it was a wonderful story.

In the middle of a bitterly cold winter I’m sure we’re all grateful to snuggle under a doona, duvet, quilt or eiderdown (the name depends upon where you live). What you may not realise is that an eiderdown was traditionally filled with eider down – the down feathers of the eider duck. And the eider duck is who this story is all about.

A quick biology lesson first. Symbiosis is a relationship between two or more organisms that live closely together where at least one of the organisms benefits from the relationship. If both organisms benefit, like in this case, it’s called mutualism.

It’s not uncommon for animals to live in a symbiotic relationship. What is very unusual is for that symbiotic relationship to be with humans.

“Eider Ducks and Eider Chicks 2018_06_03 (02)”by dbrooker1 is licensed under CC BY-NC-ND 2.0

The eider duck lives in the Arctic Circle, spending most of its time in the North Atlantic Ocean. Once a year it comes to land, Iceland to be specific, for breeding. It lays its eggs in a nest, sheds its chest feathers and uses the down to line the nest. The eider down mats together, insulating and warming the eggs.

However, when the down gets wet, it could harm the eggs.

This is where humans come in. Icelanders have been collecting the down since the Norse settled the land in about 900AD. Typically a shy bird, the eider duck lets people take the damp down from the nest and replace it with hay.

The fascinating thing is, they will only let people from their “human host family” take the down. That is, the same family that looked after their mother. This family also sits up at night and protects the nesting ducks from predators.

Once upon a time, this down kept the human host warm. These days, it’s an industry and Iceland exports the down, and provides income for the human host family.

In case you were wondering, yes, they still make eider down eiderdowns (and the odd puffer jacket). But if you were thinking of buying one, be warned, eider down is more valuable than gold. It takes 55 nests to gather 1kg (2.2lb) and only 3 tonne is exported each year. A genuine eiderdown is more than 10,000euro, or $16,000AUD, or $11,000USD. And if you were after a jacket you can order one custom made. But as eider down is expensive, rare and its use in clothing limited, you’d need to be pretty wealthy to consider it.

Once the ducklings leave the nest the birds become shy and avoid the humans. But now they’ve left their nests their human protectors are able to collect their reward… the rest of the down lining the nests.

Think about the magic of this story. There is no other way of collecting the down. You can’t cage the duck or breed it – it will only produce the down if it lives in the wild and its symbiotic partner, its human host family, protect it. A truly sustainable practice where both organisms benefit.

I think this is a wonderful story. Do you?