Mooney Goes Wild, Sunday August 13th 2017
On Mooney Goes Wild tonight: The Dipper
Dipper (photo: Shay Connolly / BirdWatch Ireland)
Take a stroll along one of our rivers or streams, and there's a good chance that you may not be the only one walking. Under the water, out of sight, one of Ireland's most interesting and unusual birds may be walking with you. The Dipper is a strange creature indeed. It's the only European songbird which forages underwater.
Clockwise from top left: John O'Halloran, Pat Smiddy, Barry O'Mahony, Niall Hatch, Manel López Béjar, Dario Fernandez-Bellon
In his new documentary, The Dipper, Derek Mooney meets with Professor John O'Halloran, Pat Smiddy and Barry O'Mahony - the UCC team who have been studying dippers for over three decades, along with PhD student Dario Fernandez-Bellon - to learn about the latest research into the habits and characteristics of this most intriguing of birds. He walks along the River Owennacurra in Midleton as Pat surveys the river, and discovers how Barry builds dipper nestboxes. He chats to BirdWatch Ireland's Development Officer Niall Hatch about the many interesting names given to the Dipper. And he travels to the Autonomous University of Barcelona, to find out from Professor Manel López Béjar how analysing a dipper's feathers can indicate the stress level of the bird and the environment.
The poem The Dipper that we hear at the start of the programme was written by the wonderful Scottish poet Kathleen Jamie, and was read by Gorretti Slavin. For more information about Kathleen Jamie's work, please do visit www.kathleenjamie.com.
For more information about UCC's Dipper Ecology Project, visit www.ucc.ie/en/dippers.
Left and right: Barry O'Mahony in his man shed in the town land of Coolatanaballey, near Carrigrohane, Co. Cork; middle: chicken wire to help grip the nesting material inside the nest box
Ringing dippers to find out more information about them
L-r: Professor John O'Halloran (UCC); Dario Fernandez Bellon (PhD student, UCC); Manel López Béjar (Prof of Embriology at the Veterinary School, Autonomous University of Barcelona)
Watch Professor John O'Halloran talk about his work on Dippers:
The Dipper is a most unusual bird. Although a passerine (a perching bird), you will always find it along a waterway. It is the only passerine that actively enters the water, swims underwater, and walks along the bottom feeding underwater. It can stay submerged for up to 30 seconds. It has a number of adaptations that allow for this behaviour (for example, strong claws, waterproof feathers, an extra eyelid etc...).
Dippers are also a very good indicator as to water pollution. They will only be found along clean waterways. They are named after their ‘bobbing’ or ‘dipping’ movements. Local names include Water ouzel, Wee water hen, and Water Colly.
Dippers are known in some areas as 'Water Blackbirds'. They have, however, the same shape as Wrens. Both birds have almost spherical bodies and little cocked-up tails. Their short necks give them a double-chinned appearance. Despite the resemblance, egg-white protein and DNA analysis show that Dippers are much more closely related to thrushes than they are to Wrens. The blackbird is a member of the thrush family, so the name 'Water Blackbird' may be appropriate after all.
But why have Dippers the same shape as wrens? The answer may lie in the size of their wings. Wrens have short little wings which enable them to fly in thick cover. Generating enough lift on small wings requires extra large breast muscles and the resulting fat breast makes for a spherical profile. Like Wrens, Dippers also have short wings, but not for flying in confined spaces. They use their wings as fins when swimming under water. Puffins, which also use their wings when diving, have a similar shape.
The Dipper's plumage is dark brown, but at a distance it looks black. A gleaming white bib extends down from the bird's chin. For all the world, the Dipper looks like a fussy little waiter in a fancy restaurant. Like the waiter, it bows and curtseys a great deal. This habit of constant dipping gives the bird its modern name. Dipping may be a form of camouflage; a bobbing bird is harder to see against a torrent of moving water. The white eye-lids, which it shows when it blinks, may have a similar function.
Dippers are placed in their own unique family, the Cinclidae. The family has only one European member but there are four dipper species elsewhere in the world. Our Irish Dipper is special; it belongs to a race peculiar to this island. Well almost, our Dipper is also found in the Outer Hebrides and in parts of mainland Scotland.
The bird is a specialist. It feeds on creepy-crawlies, particularly caddis-flies, which live in the beds of fast-flowing streams. It also takes tadpoles and small fish. Oddly, for a bird which dives for a living, the Dipper has few special adaptations for an aquatic life. Its feet are not webbed. It's legs are not especially powerful, nor are they located back towards its tail as in most diving birds. It has, however, developed a membrane which can be pulled over its nostrils when it is underwater. Its plumage is denser than that of similar small birds and its oil gland, important for waterproofing, is especially large.
The Dipper's hunting strategy is unique. It likes water with a gravel bottom and plenty of rocks and boulders. It can dive in from a perch or from flight, but, in calm conditions, it walks directly into the stream. Instead of swimming, it walks on the stream bed, turning over stones. Perhaps it would be more accurate to say that it 'flies' along the bottom. Being a bird, its body is lighter than the surrounding water and would tend to bob to the surface, but the dipper uses the current to push it downwards. It must always face into the flow. In calm water, it keeps the wings closed, but in rougher water it 'flies' under water. The dives are short, typically three or four seconds long, but durations of up to 23 seconds have been recorded. Birds may dive ten times in a minute. They like shallow water but can go down to one and a half metres.
Irish Dippers are sedentary, reluctant to leave their mountain streams. They can hunt under ice and will only leave their territories if the river freezes over completely. The mountain environment, in winter, may appear to be unduly harsh for a small bird but the water in streams, provided that it is not frozen, is warmer than the surrounding land.
Dippers tend to be solitary in winter but some remain paired. In very hard weather, the territorial system breaks down; birds face more pressing problems than defending their patch. Rival males have been recorded, amicably using the same hole in the ice.
Both partners build the nest, which is often in a hole or on a ledge under a bridge. The female does all the incubating and provides most of the food for the young. Some Dippers produce two broods in a season. Unlike most small birds, the same nest is used for both broods and may be repaired each year. Dippers take about 18 days to build their nest, much longer than most birds of their size. This encourages infestation by parasites but reusing the old nest saves time and effort.