Sunday 5 August 2018

Sanderlings and Dunlins at Farmoor Reservoir 4th August 2018

August is traditionally a peak month for waders arriving in Britain following their breeding season in the Arctic and our very own Farmoor Reservoir, landlocked in Oxfordshire, attracts its own small share of the hundreds of thousands of various wader species that come to either spend their winter in Britain or pass onwards towards southern Europe or the African continent.

Many of these waders pass overland and Farmoor's gleaming waters must stand out like a beacon as they move high overhead, and some are attracted to interrupt their long migration and drop down to the reservoir to rest and feed, usually spending a day or two along the reservoir's central Causeway, wandering along where the shelving concrete meets the water's edge. 

It is the adult birds that are first to arrive, closely followed by the juveniles making their first hazardous and instinctive journeys from their distant birthplaces, which all too soon will become uninhabitable. There is a distinct and relaxed feel to the southward migration which is in direct contrast to the urgency of the northward flight. There is no longer the pressing need to get to the breeding area, establish a territory, find a mate and rear young, all in a very short weather window but now in the lazy days of late summer, the urgency has subsided and it is just a matter of whiling away the days and preparing for the harsher short winter days to come, but which seem a very long way off on days like today at the reservoir, when the sun beats down and the air is stirred ever so gently by a warm breeze.

This was my first visit to Farmoor since the Spring and I got there early to walk the Causeway before it became too disturbed by the inevitable casual weekend visitors, windsurfers, yachts people and even fellow birders. The drought and heat of this exceptional summer have  not been kind to the fish in the reservoir and many are dying despite Thames Water taking what would look to be ineffectual measures to aereate the water. However the dying fish means that fishing on the reservoir has been suspended indefinitely which currently means the reservoir's banks are much less prone to disturbance from fishermen.

Ideal you might say for birds and you would be correct as the reservoir was deserted when I got there at 7.30 and made my way to the central Causeway to look for any waders that might have dropped in overnight. Yesterday there was an enticing report of both Black tailed Godwits and Turnstones being present along the Causeway and at this time of year hope always springs eternal, as virtually anything can turn up.

A Willow Warbler was singing wistfully, a last call for summer, as I walked along the track by the Thames to Pinkhill and the wooden entrance gate to the reservoir, whilst other juvenile Willow Warblers or Chiffchaffs were calling loudly from the hedgerows as I passed through the gate and into the reservoir's boundary.

I walked up a tarmac ramp bisecting a closely mown bank of the reservoir, the grass burnt to pale straw by the relentless sun. Several Yellow legged Gulls were standing on the small perimeter wall, eyeing me warily as I made my way up to the perimeter track. Turning onto the Causeway and looking down the length of its shelving concrete bank to the water's edge I could see a number of small waders busily feeding at the margin of water and concrete. The first two were Dunlins. Both were adults, their upperpart feathers looking very dark as the bright chestnut fringes had long since worn away revealing the dark brown centres but the frayed summer plumage feathers still had to be moulted and be replaced by  the grey and white non breeding plumage of winter.

Adult Dunlin.Note how worn and dark the feathers of its upperparts are
Dunlins are the most frequent wader visitor to Farmoor and this species can be present for many consecutive days, probably not the same birds but a continuing arrival and departure of birds heading south. Despite their almost expected presence and frequency here, they are still a welcome sight and brighten any birders day as they are usually so confiding and thus allow very close approach. 

The third wader I came across, a little further along and feeding all alone, was different. Its upperparts were a hotchpotch of black, grey and faded rufous spangling, the now very worn plumage of its summer breeding dress. The crown of its head was profusely covered with fine dark streaks and its face and breast were suffused with pale chestnut, again with irregular darker markings. It was fractionally larger than the nearby Dunlins, with a shorter, stubbier, slightly blunt ended black bill and was that other familiar small wader of the seashore, a Sanderling. They are far from common at Farmoor although one or two can, and do, turn up on both spring and autumn migration and this bird was an adult, something I have never seen at Farmoor in late summer, only on spring migration.

It was not so keen on being approached closely and flew at some distance from me, showing its distinctive white wing bars and emitting a sharp abrupt twik twik call so different to the Dunlin's more melodic and longer trill. I followed it to where it landed further along the Causeway and found that it had joined another adult Sanderling and, now in the company with another of its kind, they both seemed to gain confidence from each other, allowing me to approach much closer. I could see that the second bird was much paler and less strongly coloured than the original Sanderling. This variation in plumage colour is a feature of Sanderling's in summer plumage but soon both will be moulting into the pale grey and white of their winter plumage.

Adult Sanderling
Sanderling, although a relatively common and familiar bird on the British coast are not so in inland Oxfordshire, and I spent sometime admiring these two adults, shortly to be joined by a third, and studied their plumage which I have not had the opportunity to see so closely before.  

Sanderling, along with many other waders, are one of the world's great avian travellers and their migrations  can only be described as phenomenal. They are a circumpolar Arctic breeder migrating anything from 3000-10000 kilometres to their coastal wintering grounds in South America, southern Europe, Africa and Australia.

There are two races of Sanderling recognised, Calidris alba alba which is the one that occurs in Britain on migration and in variable numbers on our coasts in winter. The other is C.a rubida which breeds in northern Canada, Alaska and possibly eastern Siberia. 

The race C.a.alba has only a very short window of opportunity in which to breed in the extreme conditions of the Arctic Circle stretching from Greenland to north and central Siberia and both Greenland and Siberian birds pass mainly along the coasts of Britain on their way south after breeding, many continuing further along the Atlantic coast to reach as far as South Africa. The adult Sanderlings leave their breeding areas from mid July to mid August whilst juveniles follow later, from late August to early September.

I stood and looked at the Sanderlings pattering along the edge of the water and tried to imagine the lands and huge distance they had passed over to get here and the journey they had yet to accomplish before they got to their winter home. It was difficult, standing in the mundane surrounds of this huge concrete reservoir and its clutter of humanity to imagine the vast wastes of uninhabited land that these birds had looked on in the past weeks of breeding. I suppose you could call it almost fanciful to romanticise these tiny beings, which just touch down here briefly, bringing a heady combination of long distance travel and far off lands with strange names to prosaic Farmoor Reservoir and this corner of Oxfordshire but that is what I felt.

A couple of Springs ago, on a thoroughly miserable, rainy and cloudy day, a small party of Sanderling put down at Farmoor Reservoir on their migration northwards with one in particular being very strongly coloured. Now rubida the race that breeds in Canada and Alaska and eastern parts of Siberia looks very much like the bird I saw. I would not dream of claiming the bird I saw was a rubida but it was intriguing to note its strong colour tones and how similar it was to the illustrations of rubida I have seen and how different to a normal alba. There I go, being fanciful again but that surely is the thrill of bird migration.Anything is possible.

Could this be C. a. rubida or just a very strongly coloured C. a. alba?
I left the Sanderlings to carry on feeding and moving onwards came across  four more Dunlin but these were all juveniles. Gingerish brown above and profusely streaked to a lesser or greater extent all over their upper parts and without the black belly patch of the adults, they looked very different to the adults, much cleaner and sharper, fresher if you like, as their feathers were not worn at all. One at least was already commencing the moult of its juvenile upper part feathers into its winter plumage and showed a line of grey feathers on its scapulars and a patch of grey on its mantle. Soon the moult will transform the juvenile into its full winter plumage of grey and white which will make it indistinguishable from the adults which will also have undergone their own post breeding moult from  bright breeding plumage into a drab winter garb of grey upperparts and white underparts.

Juvenile Dunlins. The lower bird has already commenced moulting into
the grey feathers of its winter plumage which are appearing on the scapulars
I was pleased with my first hour at Farmoor and two Common Redshank and a lone Oystercatcher completed a nice set of waders as I moved down the Causeway. Coots are beginning to form their annual post breeding flock on the reservoir and an assembly of almost two hundred were loafing on the opposite side of the Causeway, a mixture of adults and juveniles and all for now managing to curb their aggressive nature and present a picture of harmony. In amongst them were three ducks, brown and undistinguished in their eclipse plumage but these were not Mallard but Gadwall, and another brown duck was a pleasant surprise in the form of a female Red crested Pochard, its lack of pinion feathers showing it too was moulting and currently flightless, as were the Gadwall  

Female Red crested Pochard
A sickly looking Herring Gull flopped heavily from the Causeway wall onto the water and swam away. It did not look long for this world but still retained enough strength to keep a distance between us. Many gulls seem to succumb on the reservoir at this time of year, their decomposing bodies cast up on the concrete and together with the dead and dying fish provide an easy meal for the Carrion Crows and the occasional Red Kite, the latter now a regular visitor, having learned there are easy pickings to be had here.

Herring Gull
I had almost reached the other end of the Causeway when I met two of the regulars, Tom and Dai. We had a brief chat and then Tom left us to do his monthly guided walk around Farmoor and I walked back up the Causeway with Dai, eventually leaving him at the other end to walk around Farmoor Two the larger of the two reservoirs that comprise Farmoor. I do not know why I bother as most times it is devoid of anything interesting on the bird front but I slogged around its wearisome concrete perimeter, passing a huge flock of Greylag and Canada Geese idling their time away on the sun warmed shelving concrete. They are so used to people they do not even move when you pass within a foot of them. 

I found three Teal swimming some way out on the reservoir and four Little Grebes were skulking in a far corner, all still in their summer plumage. A female Mallard with four recently hatched ducklings swam in the unsavoury green waters and three Swallows crossed the reservoir and were gone as quickly as they appeared. I completed my circuit and set about walking back up the Causeway to make my way to my car, parked beyond the reservoir in Farmoor Village.

Four birders were sat on the perimeter wall beyond the Bird Hide and they turned out to be Tom and the regular participants of his monthly walk, Sally, Terry and Peter. I joined them, glad of the chance to rest  after my long walk round the reservoir and then we all walked back to the Bird Hide.

Two of the Sanderlings were still scuttling along by the water's edge and a plan was hatched that we could maybe get some good close up photos of them from the Hide with Tom gently chivvying them along towards the Hide by walking slowly behind them on the Causeway as we sat, cameras poised inside the Hide. For once a hastily agreed plan came to fruition and worked perfectly thanks to Tom's kind co operation. Slowly the two birds came closer and then closer still, stopping every so often, unsure and anxious and looking as if they wanted to go back but Tom's presence on the Causeway persuaded them otherwise. I am sure they were suspicious of the Hide's open viewing slats from which we were looking out but they seemed to overcome their reservations and carried on towards us until they were almost up to the Hide and we duly got some lovely images of these delightful waders. 

After the Sanderling had passed the Hide I looked around the interior which frankly was in a bit of a state. There are plenty of rubbish bins available around the reservoir but it seems the Hide is also considered a suitable place to leave rubbish and there and then I suggested we give the Hide a clean. 

I reasoned we could get a black plastic bin bag from the cafe and a broom from the Ranger's office and set about it immediately. This spontaneous outbreak of social conscience on my part was endorsed by Sally and Peter, for which go my thanks and gratitude and so we walked back down the Causeway to get the required plastic bag and broom from the cafe and office while Tom and Terry continued their guided walk. 

An adult Common Tern was loafing on one of the pontoons that are used by the currently absent fishermen.They too are beginning their moult, preparatory to their long migration south and the black cap is being replaced by white feathering on the forehead giving the birds a grizzled look.

Adult Common Tern
We returned to the Hide and set about a twenty minute clean up of its interior. Apart from the accrued rubbish there was a phenomenal number of spiders and their webs but we dutifully wiped down the walls, ceiling and all the benches. It did not take that long or require such a great effort and afterwards the Hide did look much better. I just hope it remains so but have my doubts.

Anyway, feeling thoroughly righteous we repaired to the cafe for coffee and a chat and that was my morning at Farmoor. Sally very kindly took pity on me and drove me all the way back to my car on the far side of the reservoir, as according to my i-phone I had walked 5.9 miles this morning but I had enjoyed every minute. Well almost! 

Please click on any image to view a larger version

No comments:

Post a Comment