Dippers

Of all the pages on this website this is the one that has been the longest in the making purely because I have waited around six years to get a half decent photograph of a Dartmoor Dipper. Don’t get me wrong it’s not that I haven’t seen one, quite the contrary I’ve seen plenty flitting up and down various rivers, streams and leats but none of them would stand still long enough to take the shot. That is until March the 22nd 2014 when on a walk through Fingle Woods when everything changed. Just like the proverbial ‘waiting for a bus’ that day the Dippers were all along the river Teign and in no hurry to be anywhere which provided an opportunity to get that elusive photograph. If there was ever to be a bird which represented the Dartmoor National Park then in my opinion it has to be the Dipper.

It has always been said on Dartmoor that you always hear them before seeing them and usually then the sighting is a very brief one as they skim the waters like low level fighter pilots. Their wings make a distinctive in-flight whirring sound somewhat akin to the noise a Hummingbird makes whilst hovering. Having heard that sound the next thing is usually a flash of white darting low over the water which is sometimes accompanied by their unmistakable chirping song. Should they alight on a rock the bird then begins its dipping up and down routine from which it takes its name – the Dipper. Another local name for the bird is the ‘Water Ouzel’ due to its vague similarity to blackbirds. To be really official its full name is the White Throated Dipper or to be scientific Cinclus cinclus.

There are those who will say that the Dipper has the unique and remarkable ability to swim under water but this is not really the case. It’s short muscular wings act as a pair of miniature flippers which allow the bird to stabilise its weight and walk along the bottom of the river or stream. To aid in this their blood is exceptionally high in haemoglobin which enables them to store higher levels of oxygen thus allowing them to remain underwater for up to thirty seconds. The dipper is also equipped with highly developed focus muscles which alter the curvature of their eye lenses thus improving their underwater vision. Additionally nature has provided them with nasal flaps which prevent water entering their nostrils. Top this off with two sets of long, sharp claws which are ideal for gripping rocks in fast flowing waters and you have a highly adapted bird for living in a watery habitat.

On Dartmoor the Dipper population is present along many of the rivers, stream and leats. One of the most accessible places to spot one is along the East Dart river at Postbridge where they can often be seen near the old clapper bridge. However, nationally their numbers are said to have decreased by around twenty five percent. Apparently Dippers are exceptionally  sensitive to water acidity and water bourne pollution which has lead to the decline. The main culprit for river acidity is coniferous trees situated near to water as they trap acidic water pollutants. These then leach into the waterways and kill of the invertebrate prey lthat the Dipper feed on. It is also suspected that the acid pollution may lead to a calcium deficiency in the birds which leads to weak eggshells that never survive.

On the plus side it has been noted that their breeding performance has improved thanks to ‘climate change’. This has meant that the warmer weather has enabled them to lay their eggs much earlier and in some cases hatch more than one brood. As mentioned above, the warm winter of 2013/14 certainly had provided an opportunity for the Teign Dippers to begin nest building. This may well have been the reason why there were so many photographic opportunities, the birds were busy collecting nesting material.

A survey conducted by the British Trust for Ornithology in the early 2000s found that on a 4.4km section of the river Plym (between Shaugh Bridge and Legis Tor) there were an average of 2.13 pairs of birds. This gave an overall number of .48 pairs of Dipper per kilometre. Similarly on a 6.5km stretch of the river Meavy below Burrator there were 4.85 pairs giving a figure of 1.34 pairs per kilometre, Smaldon, p.145.

So, what’s the annual life of a Dipper? Once nature and the climate tell the birds that its time to breed they begin nest building. On Dartmoor their favoured sites are in natural holes or man made structures such as bridges. The nests are built from various water mosses and riverside vegetation, these are then lined with dry leaves, wool, etc. The constant threat to waterside nest sites on Dartmoor is that should the river levels dramatically rise, as they often do, there is a strong possibility that the nest will get flooded. Clearly if this happens when there are eggs or chicks in the nest then that sadly is the end of that brood.

As mentioned above, the birds can often be seen standing on rocks tugging out the moss then flitting to their nesting site. Both birds participate in nest building and it normally takes them around 28 days to complete the task. Once built the eggs are laid at daily intervals and clutches comprise of between 4 and 5 eggs. However were the waters are acidic they tend to be smaller, it’s as if the birds know their food supply will be less. The eggs are then incubated for roughly 16 days with the last egg to be laid being first in line, this then means they all hatch at the same time. The chicks then stay in the nest for approximately 12 days during which time both parents will take up feeding duties. The youngsters will fledge at between 20 and 24 days but will continue to be fed for a further 7 days. The young become fully independent after 11 to 18 days after leaving the nest. Where a second clutch is to be laid this will take place 10 days after the first brood have fledged.

The Dippers staple diet consists mostly of aquatic invertebrates such as Caddisfly larvae, May Fly nyphs and even small fish such as minnows. It has been estimated that 66% of each day is spent foraging for food which is why they always look so busy.

Once that particular year’s breeding has been completed some birds will migrate whilst most will remain on their territory and basically ‘chill out’ until the next season when the cycle will begin again.