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. . .
Whilst setting up the public information desk this morning I saw my first migrant Fieldfares of the season. Unmistakeable with their grey heads and backs, there were just three or four birds at first with a couple of Redwing as companions, easily confirmed through the spotting scope. Then one or two more, very timid and obviously nervous of the unfamiliar sounds of car engines and dog barks. They were feeding in open ground under the large hawthorne tree by the stone wall and retreating back into the sanctuary of the tree at the slightest noise. On and off throughout the morning they were there, giving some of our visitors great views of their first Northern European visitors. Just after noon they took off in a small flock of about a dozen birds, towards the western end of the field and into the high trees along Bradburys Lane. Later they returned to feed in the hawthorne, now in a flock of about twenty. Look out for these birds as their numbers swell over the coming weeks.
On Sunday 7th November I will making my third attempt to lead the Yeoman Hey walk I hoped to do on the 26th September and 3rd October. On both the previous days the weather was so bad that it would have been impossible to see anything or even carry out the briefest conversation about the area or its wildlife! Although we will getting towards the back end of Autumn by the 7th, there should be lots to see as the winter visitor numbers increase by the week. The most likely birds at Dove Stone will be Redwing and Fieldfare from Scandinavia, together with increasing numbers of goldcrest, goldfinch and mistle thrush as Northern European visitors join the residents to swell their numbers. There may also be siskins and redpoll to be seen and who knows, the crossbills might be around in the woods near Bin Green. (Don't hold your breath!). There are always good numbers of long tailed, coal and blue tits in the connifer plantation above Yeoman Hey. A cormorant and great crested greebe have been regular visitors to Yeoman Hey Reservoir recently
The walk is a fairly gentle stroll of about four miles, with only a little climbing but parts are now very wet and boggy, especially on the return leg to the east side or Yeoman Hey, so boots are a must. We will probably take about two and a half to three hours to do the route, with numerous stops for information and observation.
I look forward to seeing you on the 7th.