Nick Baker’s Hidden Britain
The shoveler duck’s surprising talent
The ducks, their polychromatic heads sparkling in the low winter sun, spun around and around almost on the spot. These northern shoveler ducks were among the many other species of what are often termed dabbling duck.
There were wigeon, gadwall, teal and the ubiquitous ‘duck pond duck’ the mallard. They each had their own sport: the teal worked around the edges of the reeds in the shallows, the gadwall in the open, the mallard mid-water, often up-ended, the wigeon leaving the water entirely and grazing the surrounding short vegetation.
However it was the motion of the shovelers that set them apart, and because they were close to the hide in which I sat, it was the sound they made too – a bright, rhythmic but continuous splashing, like a fast dripping kitchen-sink tap.
What are they doing? Well it’s clear they’re feeding – but on what? And how? It’s part of the fascination of birdwatching – trying to spot the niches that different birds exploit. While the rafts of floating seeds of plant material, the submerged vegetation and grass growing around the edges make some sense as a food source, the water that the shovelers were ‘shovelling’ seemed to be just that – water (slightly turbid, green/brown water, but water nonetheless). It seems that these spectacular looking birds were conjuring up all their winter energy from the murk.
Take a drop of this green murk and stick it under a microscope at 30x magnification, and it becomes a nutritious soup – a seething, fizzing mass of little lives from tiny protozoa to relative giants in the form of the creatures eating them: midge larvae, daphnia and cyclops, beetles and water boatmen – a good meal for those tooled up for the job. As you’ve probably guessed, this duck’s success has something to do with the incredible spatulate hardware stuck to the front of the bird: at around 7cm long, its bill is longer than the head itself.
The shoveler is a specialist at soup straining. While many of the other dabbling ducks have a series of comb-like serrations called lamellae on the inside edges (tomia) of both upper and lower mandibles, allowing a degree of filtering, the shoveler takes this design feature to another level.
Compared with a mallard, a successful generalist, which has 50–70 of these short and stubby lamellae, the shoveler has about 220 on its lower mandible and 180 on the upper.
But it’s not just the number of these combs that is spectacular; they are long, too – some approaching a centimetre. They are in effect similar to the baleen plates of a whale, and in some respects the feeding mechanism isn’t dissimilar either.
While these lamellae are hidden from view most of the time, there is a section of the bill which looks like the upturned corner of a smile – actually called the grin gap – and in good light, you can just about make them out.
The upper mandible fits over the lower one, and when the bill is half open the lamellae in the top and the bottom mesh together forming a filter cage. And this extraordinary bill design is only part of the story: when coupled with the avian world’s most bizarre tongue ( see left), it becomes a highly effective filter pump, too.
NICK BAKER is a naturalist, author and TV presenter.