Dipping: Dippers doing what they do. . .

Autumnwatch viewers might have seen an interesting piece on the programme this week by a sound recordist who was recording the song of the Dipper ( and the bird’s sub-song;  basically a bit of a practice for the year ahead when song really comes into its own ).   Here's a link to their song ( as well as some more info on Dippers and breeding ): http://www.rspb.org.uk/wildlife/birdguide/name/d/dipper/index.aspx.

This year we’ve regularly seen Dippers at Dove Stone,  including several young birds.  So let’s talk Dipper some more.  Frequently seen along Chew Brook and along the water channels running alongside Yeoman’s Hay and Greenfield reservoirs as well as on occassions by the shores of the reservoirs,  Dippers feed underwater on caddisfly larvae and other aquatic insects.  

So how do Dippers do what they do ?  Dippers have a gland above their tail that contains waterproof oils which they dip their bill into to give them a thicker waterproof coat.  They also have a thick undercoating of down feathers which gives them insulation to manage cold water temperatures.

In addition they have a movable flap over their nostrils that closes when they’re underwater.  Clever.   Underwater sight is helped by a third eye lid ( otherwise known as a nictitating membrane ).  This acts a bit like a windshield wiper.  The Dipper can also store greater quantities of oxygen in its blood because of high concentrations of  hemoglobin.  In short this allows the Dipper to spend longer amounts of time foraging underwater.

But what about the dip;  why do Dippers dip ?  Its been observed that dipping and bobbing becomes more intense when a bird is agitated.  Apart from this possible explanation there are a couple of other theories.  Dippers are better able to pinpoint locations of aquatic prey by taking visual information from more than one vantage point;  maybe the relentless up and down motion changes the light angle, allowing dippers to see into the water.  Another theory is that Dippers sometimes communicate with each other by dipping instead of vocalising when stream noise makes movement more detectable than song  - except that dippers sometimes dip even when they're alone.  Perhaps our sound recordist might also question the credibility of this particular theory ?

Whatever the reasons,  the fact remains that the Dipper is a fascinating bird and you can see all of this first hand ( with a bit of time,  patience and luck ) at Dove Stone.  Here’s a link to a video on you tube of the Dipper http://www.youtube.com/watch?v=Fqusf8U-ZAI

There are some other videos of varying quality on youtube that capture better the Dipper in fast flowing streams,  including footage of Dippers flying in and out of waterfalls.

More Dove Stone news soon. . .