Don’t dip on DIP­PERS

This unique British bird is all too easy to over­look, so make sure you don’t miss out on see­ing one, says Ian Par­sons

Bird Watching (UK) - - Con­tents -

AHIGH-PITCHED CALL FOL­LOWED by a whirr of wings that blurred the shape of the bird as it flew low over the fast-flow­ing wa­ter, sig­nalled the ar­rival of a Dip­per. Land­ing on a rock mid-stream, the bird gave its char­ac­ter­is­tic bend at the knees, be­fore it walked head­long into the tor­rent. All of this hap­pened right in front of me as I stood on the pave­ment look­ing down at the East Lyn river in north Devon, where, af­ter plung­ing off the high ground of Ex­moor, the river meets the sea at the charm­ing vil­lage of Lyn­mouth. Now, de­scrib­ing this as ur­ban bird­ing might be stretch­ing it a bit – af­ter all, the ac­tual pop­u­la­tion of Lyn­mouth is only a few hun­dred peo­ple – but it was a late sum­mer’s day, the road was busy with traf­fic, the pave­ments over­flow­ing with tourists and the shops and cafés were do­ing a roar­ing trade. As far as Ex­moor goes, this was ur­ban! De­spite all the noise and bus­tle go­ing on around me, though, I was able to look down and watch a bird that is as­so­ci­ated with the wild, un­pop­u­lated ar­eas of Bri­tain, prov­ing that you can see great birds in the un­like­li­est of places. The Dip­per is in­deed a sym­bol of wild places. It is also a bird that had of­ten proved to be a bit of an enigma for me. To put it sim­ply, I al­ways used to ‘dip’ when it came to see­ing Dip­pers! Many bird­ers have bo­gey birds, and the Dip­per used to be mine. I would go to the right places to see it, spend time wait­ing and watch­ing, but for some rea­son I just wouldn’t see them. The frus­tra­tion would then, of course, be com­pounded when an­other birder would glee­fully in­form me that they had seen one at the ex­act same spot the day be­fore. There is no rea­son for this to hap­pen, of course, it is just one of those things, and there is a so­lu­tion. Per­se­ver­ance, pa­tience and a bit of re­search are the best way to over­come trou­ble­some species. I asked other bird­watch­ers where they saw Dip­pers reg­u­larly and in­stead of hav­ing one site to visit, I got to know sev­eral.

I also re­searched their calls, and it was once I had learned that high-pitched flight call that I started to spot Dip­pers. Learn­ing a bird’s song or call is a great help to find­ing that bird in the wild. Nowa­days, I have no trou­ble find­ing this wa­ter-lov­ing bird, even turn­ing it up in un­ex­pected places, as I have ex­plained. Ev­ery time I see one, I en­joy it, for they re­ally are spe­cial birds. No other passer­ine does what the Dip­per does; its abil­ity to dive into and swim and walk un­der­neath the wa­ter makes it unique. Watch­ing one walk head-first into a fast-flow­ing stream makes you re­alise what a spe­cial­ist this bird is. It might look ‘or­di­nary’, sort of a dumpy­look­ing thrush in ap­pear­ance, but to do what it does takes some very clever adap­ta­tions, in­deed. All fly­ing birds have evolved a spe­cial­ist bone con­struc­tion that re­duces their body­weight yet max­imises the strength of the skele­ton. The bones have a hon­ey­comb-like struc­ture to them, mak­ing them ba­si­cally hol­low yet still very strong. All fly­ing birds that is, other than the dip­per fam­ily. Dip­pers are unique in that their bones are solid,

the den­sity and weight of th­ese bones mak­ing them a lot less buoy­ant, some­thing that is im­por­tant when your food can only be found un­der the wa­ter’s sur­face. The ex­tra weight that Dip­pers have in com­par­i­son to other birds of a sim­i­lar size may ex­plain the fre­netic whirring wings of the bird in flight – ba­si­cally, it is hav­ing to put a lot of ef­fort into get­ting that ex­tra weight air­borne. Their feet are very strong, with sharp claws that en­able them to grip stones on the river bed. This, com­bined with pro­por­tion­ally long legs, helps them to re­sist the flow of wa­ter that is push­ing against them. They are able to swim un­der wa­ter thanks to well-de­vel­oped mus­cles in their wings, and the added strength from th­ese mus­cles means that

The Dip­per might look ‘or­di­nary’ but to do what it does takes some very clever adap­ta­tions in­deed

they can use their wings like flip­pers, pow­er­ing them­selves through the cur­rent as they search for food. This search is also aided by a spe­cial adap­ta­tion to their eyes, which en­ables them to change the cur­va­ture of their lens and fo­cus them un­der the wa­ter just as eas­ily as when they are on land. Cou­pled with that, their ears have a flap of skin that can be tight­ened to en­sure that they don’t get clogged with wa­ter when the bird sub­merges it­self. This is a bird with ‘su­per­pow­ers’, but the su­per­pow­ers don’t stop there. As you would ex­pect with a bird that spends much of its time sub­merged in moor­land streams, pro­tec­tion against cold wa­ter is es­sen­tial. The feath­ers on a Dip­per are ex­tremely dense, pro­vid­ing a thick layer of in­su­la­tion that the bird reg­u­larly main­tains us­ing an en­larged preen­ing gland. This en­sures that their feath­ers stay as wa­ter­proof as pos­si­ble. Dip­pers feed on aquatic in­ver­te­brates found in the river and stream beds. Th­ese are of­ten hid­den away, which means the bird has to hold its breath while it searches for them. They can hold their breath for as much as 30 sec­onds, a re­mark­ably long time for a bird about the size of a Star­ling! To help them with this, they have an­other two adap­ta­tions. Firstly, their meta­bolic rate is much slower than a sim­i­larly-sized ground-dwelling

ÈCOURTSHIP FEED­ING Adult Dip­pers in­dulge in a spot of courtship feed­ing

passer­ine. Se­condly, their blood has a much greater ca­pac­ity for hold­ing oxy­gen than other sim­i­lar-sized birds. What this means is that they don’t need to breathe as of­ten as other birds and when they do take a breath, it lasts longer in their sys­tem than in other birds. Dip­pers are an ex­cel­lent ex­am­ple of how evo­lu­tion has honed a species to fill a par­tic­u­lar niche. So where can you find th­ese su­per-powered birds? Dip­pers are gen­er­ally up­land birds and are found in Scot­land, Wales, north­ern Eng­land and south-west Eng­land. They love fast-flow­ing streams and rivers, with plenty of rocks and boul­ders to cause tur­bu­lence in the wa­ter, and also to act as perches. In win­ter, par­tic­u­larly a harsh one when wa­ter­courses higher up are prone to freez­ing, in­di­vid­ual birds may move to more low­land habi­tats and even, on rare oc­ca­sions, the coast. Make sure you en­joy the unique­ness of a Dip­per soon.

CHECK­ING FOR GRUB Dip­pers like to look un­der the wa­ter’s sur­face to see what is there, be­fore plung­ing in to pick out food

ÈTASTY MORSELS Dip­pers mainly feed on aquatic in­ver­te­brates, but will also take small fish BRING­ING IT HOME A Dip­per brings a beakful of in­ver­te­brates back to its stream­side nest

STRONG FEET Dip­pers have large, pow­er­ful feet, for gripping onto slip­pery sur­faces

é GREY YOUNG­STER Young Dip­pers are grey above, paler be­neath, so easy to iden­tify

é HAPPY UN­DER­WA­TER Dip­pers can walk along the bot­tom of a stream as well as ‘fly’ un­der­wa­ter to swim

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