Discover the dipper, the remarkable Dales bird that ‘flies’ underwater, Brian Pike reports
High on any list of the Dales’ most attractive features must be the many streams and rivers that tumble merrily over cobbles, boulders and rocky outcrops as they rush towards the North Sea. Autumn is the perfect time of year to take a stroll alongside one or other of them, pausing perhaps to rest by a scenic waterfall. And if you keep your eyes open there’s a good chance you’ll spot one of our most unusual native birds: the dipper.
The dipper isn’t especially colourful, but there’s no mistaking it. It’s small, stout and perky, with a slightly up-tilted beak. Its plumage is a mix of chocolate brown and sooty grey, thrown into vivid contrast by a large, snowy-white throat patch. No other British bird looks even remotely similar – apart, perhaps, from the larger, darker and much rarer ring ouzel.
Just in case you’re in any doubt, though, dippers draw attention to themselves by making a distinctive motion when they are perching near water. They will bob up and down on the spot by quickly bending and then straightening their legs, often accompanying each ‘curtsey’ with a flick of the wingtips. This is the ‘dipping’ that gives them their name.
Dippers are passerines, that’s to say they are songsters that belong to the same group of birds as the familiar house sparrow. Distant relations they may be, but their lifestyles could hardly be more different. Dippers are found exclusively near clear, fast-moving, unpolluted water, which is why our Pennine hills are one of their strongholds. The species is almost entirely absent from lowland Scotland, the Midlands, Home Counties and the South East of England.
Dippers are found exclusively near clear, fast-moving, unpolluted water
White-throated dipper, aka European dipper, Cinclus cinclus.
WHEN TO SEE THEM
The dipper is resident in the UK, hence can be seen all year round. If upland streams are frozen, dippers may temporarily relocate further downriver.
Dippers are on the UK amber list. Populations have declined significantly in recent years, possibly because of the changes to watercourses caused by acid rain.
The RSPB gives a remarkably broad estimate of the breeding population as being between 6,200 and 18,700 pairs. Presumably this means nobody is entirely sure quite how many there are.
Length 18cm. Wingspan 25–30cm. Weight, 55–75g.
The male has a warbling courtship song similar to the wren. Both sexes make chirping calls that are sufficiently high-pitched to be heard by other birds above the noise of the river.
Dippers lay two clutches of 4–6 eggs per year, beginning in late winter or early spring. Dipper nests are domed constructions of stems, moss and leaves, often located in rocky crevices in the riverbank or behind waterfalls. Both males and females cooperate to build them. Nest sites are occupied by successive generations of birds, and one particular site has apparently been in use for at least 120 years. Individual dippers live to around eight years old.
The dipper has been adopted as the national bird of Norway because it’s such a well-loved sight on the country’s icy-cold mountain streams.
THE LIFE AQUATIC
Dippers prey on small fish, insect larvae, shrimps and other invertebrates that they find under rocks and stones. Their choice of diet isn’t especially remarkable, but what makes them unique is the way they hunt for it. They start by gripping the rocks firmly with their long toes and then walk upstream, usually until they are wholly submerged.
Amazingly these little birds can stay underwater searching for food for half a minute or more. But this raises an intriguing question: how can such a tiny bird manage to stay submerged, let alone stop itself from being swept away by the powerful current?
Part of the answer lies in the dipper’s bone structure. Most birds have hollow bones, designed to make them lighter and more airworthy. The dipper, by contrast, has solid bones, increasing its weight and making it significantly less buoyant.
The other factor that makes the dipper capable of coping with torrents that no other small bird would dare to enter is the way it uses its wings. Effectively it ‘flies’ underwater. But whereas a bird taking to the air uses its wings to get lift, the dipper does the opposite: it angles its wings so that the rushing water passing over them presses the bird downwards instead of lifting it up. When the time comes to return to the surface, the dipper changes the pitch of its wings and ‘flies’ to the surface.
The dipper has several other adaptations to help it hunt underwater, including waterproof feathers, blood that’s modified to store extra oxygen, and a slower than average metabolic rate. A dipper can close its nostrils with special flaps to stop water getting in, and also alter the curvature of the lenses of its eyes to enhance underwater vision.
If you’re lucky enough to observe dippers feeding, you’ll find that they generally pop up a fair distance from where they entered the water, having travelled beneath the surface in search of prey. Observe carefully, though, and you may just be able to track their underwater progress – and predict where they will reappear – by spotting a trail of tiny bubbles.