I spent yesterday photographing waterfowl at the London Wetland Centre.
I was reminded of the inductive reasoning ‘duck test’: “If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck”.
At first glance, this is reasonable enough (for those of you having sensation of deja vous, don’t worry, it isn’t a glitch in the Matrix, it is because you might remember this previous post).
I am sure if I showed most people this photograph, they would tell me it is a duck:
You wouldn’t need to know that it was a Eurasian Wigeon (Anas penelope), to be able to correctly assume that it was a type of duck.
But what is it about a duck that tells us it is a duck?
Also, I would hazard a guess that a reasonable minority of people, if they had joined me yesterday, would have told me that this Little Grebe (Tachybaptus ruficollis):
…or this Eurasian Coot (Fulica atra)…
… were ducks. They are not.
So I conducted some scientifically robust polling of non-birding friends and family to try to find the answer: what is a duck?
The answers I received were remarkably similar: ducks live on (or like) water. Some people were more specific about habitat – informing me that ducks “like lakes”; whilst others gave me further clues about behaviour, telling me that ducks are not very good at flying.
Whilst the Coot and the Little Grebe, might confuse a few people, I would guess that fewer people would be fooled by this:
That was, of course, a juvenile Great Crested Grebe (Podiceps cristatus).
And I doubt (I hope!) anybody would think this Common Snipe (Gallinago gallinago) was a duck:
Both of them are water birds, but they just don’t look like ducks – largely because they have completely different bills. So, it can’t just be their love of water which makes them ducks.
But then ducks do share many physical characteristics with swans and geese such as Mute swan (Cygnus olor):
…and Egyptian Goose (Alopochen aegyptiacus):
But my fictional companions would be able to identify them as swans and geese respectively, largely because of their size and neck length. But here is the rub…
Swans, geese, and ducks are all part of the same scientific family: Anatidae. OK, that isn’t particularly surprising. But what if I told you that that the Egyptian Goose wasn’t really a goose at all. It belongs to a sub-family called Tadorninae, which mostly includes shelducks and other large ducks.
So, there is a blurry area on the edges of the duck family, but there are a whole number of ducks (about 80 species) where you would have no difficulty in labelling them ducks.
But there remains great variety in this grouping.
The biggest genus is ‘Anas’, often labelled the dabbling ducks. Such as this Northern Shoveler (Anas clypeata):
… the wigeon we saw above, and this beautiful Northern Pintail (Anas acuta)…
…like many ducks found in the UK, the birds above are migratory, and sometimes fly thousands of miles twice a year to spend the winter in warmer climes than their homeland in the frozen north. So, some ducks fly very well (although others have almost lost the ability to fly altogether, such as the torrent ducks).
The word duck comes from the Old English verb, ducan, meaning “to duck or dive”, and it is appropriate for a large number of diving ducks, such as the Tufted duck (Aythya fuligula)…
And so, I shall end with the words of a far wittier man than me, Douglas Adams, who answered the question both accurately and amusingly:
“If it looks like a duck, and quacks like a duck, we have at least to consider the possibility that we have a small aquatic bird of the family Anatidae on our hands.”