Dipper
The bird of the torrent, and the UK’s only aquatic songbird
Last month I was lucky enough to spend a week in the Highlands of Scotland, where we hiked, swam, botanised, birded and ate and drank our way around the Cairngorms. We had so many amazing experiences while we were there, which isn’t surprising as it is an amazing place to encounter wildlife, but my most memorable moment of the holiday was canoeing on Loch Morlich and deciding to disappear away from the few other people that were on the loch, by paddling up the River Luineag. As we chartered the peaty brown flowing water, we were met by one of my favourite birds, the dipper (Cinclus cinclus).
It’s a timid bird, which when spotted normally takes flight, whirling speedily away just above the water out from sight. But this one in particular was not timid at all; I think that being sat in a canoe masked our form and the fact we were humans, so the bird went about its business without any hesitation and carried on hunting for prey underwater, reemerging to perch on a log with several beak fulls of freshwater shrimps and small fish, right by us in the canoe, whacking and feeding on its prey within 2 metres of us as we sat there in complete awe and silence – even the toddler was quiet, which is a miracle!
Dippers are a medium-sized, plump, short-tailed, chocolate-brown-coloured bird with a white throat and chest, often seen sitting on a stone or protruding log on fast-flowing clean rivers or streams in upland areas, Wales and the South West of England, bobbing up and down when perched and speedily flying low across the surface of the river. They are an indicator species of good water quality because their prey of mainly aquatic insects is very sensitive to changes in water, and so the appearance or disappearance of dippers is symptomatic of changes in river quality.
Known just as ‘dipper’ in the British Isles, the name represents a genus that has four other species: rufous-throated dipper (Cinclus schulzii), American dipper (Cinclus mexicanus), white-capped dipper (Cinclus leucocephalus), and brown dipper (Cinclus pallasii). Many scientists offer varying reasons why they ‘dip’; Stephanie Tyler MBE, a well-known ornithologist who has studied all five species of dippers from the Himalayas to Canada intensively for 40 years, says “there is no definite reason why they do”, and we have focused on one of the less impressive characteristics of the bird!
The dipper is Britain’s only aquatic songbird, with fascinating adaptations allowing it to thrive in both air and water – some seen and some unseen. Dippers have high levels of haemoglobin in their blood, enabling them to store large amounts of oxygen while underwater. They have flaps that seal their nostrils from water, and well-developed muscles controlling the shape of their lenses to counteract the visual difficulties of refraction in water. It also has a wetsuit-like plumage, which has one and a half times as many body feathers as a blackbird, which are well-oiled using its enormous preen gland at the base of its tail. These slick feathers trap thousands of air bubbles underwater, making it silvery looking when diving, which camouflages its brown body from its prey. As soon as it reappears on dry land, it gives a little shake and all the pearly water droplets fly off in an instant.
So, what are they after when they are hunting underwater? For the most part, dippers hunt mayfly larvae, nymphs, and caddis, all of which are generally clinging to the undersides of rocks, hiding from fast-flowing water and predation. Dippers’ ability to stay underwater is not due to webbed feet, even though they can swim excellently, but due to their short but strong flipper-like wings, which beat the bird down to the bottom, and their vice-like crampon claws allowing them to walk along the river bed and find their prey. They drag their meals from the underside of rocks to above water, where they beat them repeatedly against a stone or log, whichever is its feeding post!
Dippers reach sexual maturity in their first year and nest early before the end of February, laying four to five white eggs, which are laid in daily intervals. The nest is a domed, mossy structure hidden in a stone wall, a crevice in a bridge, or behind a waterfall. The eggs are incubated for 16 days and brooded by the female until they are 12-13 days old, with both parents feeding the young. Dippers fledge after three weeks and take to the river, rather clumsily to begin with, but after 20-30 days, they are almost as good as their parents, fearlessly hunting in torrents. Ten days after fledging, a second clutch will be started.
Sadly, the way rivers have been mistreated has had an effect on dipper numbers, pushing them into amber UK conservation status. Throughout the river network, numbers are declining and have been since the 1970s, with about 6,900-20,500 UK breeding pairs left. Acidification (acid rain and coniferous trees close to streams and rivers) reduced aquatic life and caused a calcium deficiency in egg-laying; industrial pollution and sediment in watercourses has suffocated aquatic life; and hydroelectric developments and irrigation have reduced flows in Europe. But there are some success stories of dippers recolonising formerly polluted waterways through towns and cities.
There is no specific conservation action for dippers, since they are not under threat, but general conservation work is being done to reduce pollution entering watercourses, which will benefit dippers.
So, if you are on the riverbank, keep an eye out for this little delight and I challenge you to try to get a photograph as I have never been so lucky!
This Species of the Month is dedicated to GWCT member Richard Spencer. Thank you for your encouragement at the Game Fair!
Megan Lock
Advisory
Image credit: Mark Medcalf