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| Pallas's Leaf Warbler ( curtsey and copyright of Nick Truby) |
Yes, believe it or not, sewage works are the place to be for a good spot of winter birding! They create a microclimate warmer than the surrounding countryside that can host a large fauna in the cold winter months. Birds are often attracted to this microclimate by the large numbers of insects not found elsewhere in winter. This includes resident flocks of birds such as Tits and Finches but also birds that normally migrate such as Chiffchaffs. I’ve discussed the evolutionary advantages and risks of Chiffchaffs staying put in winter rather than migrating before, see here. In amongst the Common Chiffchaffs at sewage works it is also sometimes possible to find the much rarer Siberian sub species.
The Abingdon sewage works in Oxfordshire, quite close to where I used to live, is renowned for its wintering flocks of Chiffchaff which have included one or two Siberian Chiffchaff for, I believe, at least the last 25 years.
Last week Oxon birder Gareth Blockley was looking at the Chiffchaffs when he found something much much rarer, a Pallas’s Leaf Warbler. Although its possible to see these rare vagrants most autumns on the east coast, this was the first record for good old landlocked Oxfordshire – a very big well done Gareth!!!
Pallas's leaf warbler (Phylloscopus proregulus) breeds in mountain forests from southern Siberia across to north-eastern China. It is named after the German zoologist, Peter Pallas, who first formally described it. It is migratory wintering mainly in southeast Asia although recently increasing numbers have been found in Europe in autumn. It is a small bird, not much larger than a Goldcrest, with a relatively large head, short tail, greenish upperparts and white underparts, a lemon-yellow rump, and yellow double wing bars, supercilium and central crown stripe.
I was chatting to my birding friend Jeremy on Wednesday night who lives in Oxon and explained that I was planning to go for the Pallas’s on Thursday. He had a couple of other things to do but said that he would try and join me. My plan was to arrive mid-morning when the warming sun would bring the insects onto the wing. An uneventful drive had me on site around 10:30 where a small group of birders were searching the hedgerow surrounding the sewage works. I was told that the warbler had just been seen in the hedge and sure enough after a few minutes I had my bins of this beautiful little gem. Jeremy arrived after a few minutes and also enjoyed views of this winter wonder. It was always quite deep in the hedge, never really perching up for photos, but none the less watching it flit restlessly through the hedge feeding on insects certainly warmed my heart on this bitter cold winter day. After a while we lost sight of the bird and the other birders started to drift away content with their views. Jeremy and I spent another couple of hours on site trying to relocate the warbler and going through the large flock of Chiffchaffs looking for Sibs. It was impossible to estimate how many Chiffchaff were present but I’m sure that this is the most I have seen in one flock. Who would have thought it on a bitter cold winters day when most of their brethren would be sunning themselves in Africa! In books Sib Chiffchaffs look very distinct from our common Chiffchaffs but as I’ve said many times before, out in the field it’s a different matter with individual birds changing appearance remarkably as then move through differing lighting conditions. As its name suggests, it breeds in Siberia and winters in the lower Himalayas. In general, it is duller than its common cousin being grey or brownish above and whitish below, with little yellow in the plumage. The absolute definitive features of a Sib are its song and call which are very different to our Common Chiffchaff. Although the Common Chiffchaffs would occasionally burst into song, we never head a Sib call or sing. However, we did find one very strong candidate based on appearance. It was truly surreal to hear the Common Chiffchaffs singing on such a bleak winters day, a sound I normally associate with early spring. The Pallas’s Warbler is known to wander quite widely on the site so we widened our search to a small wood at the end of the lane. We had no further sittings of the Pallas’s but a small flock of Siskin and Repoll feeding on the Alders were new year ticks for me.
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| Pallas's Leaf Warbler ( curtsey and copyright of Nick Truby) |
I decided to make a move and drop into Farmoor on the way home to see a showy juvenile Great Northern Diver while Jeremy headed off to Otmoor to finish his days birding.
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| Siskin |
I arrived at a cold bleak Farmoor and set off along the causeway scanning F1 where the diver was said to be. I reached the end of the causeway with nothing of note sighted apart from a new for the year Common Sandpiper. I had heard that the diver was sometimes on the far side of F1 so set off to walk around the reservoir. Halfway around I met Oxon birder Steve Roby who had also not seen the diver. We agreed to phone each other if we saw the diver and I continued with the long walk around F1 with no sightings. I arrived back at the car and checked my phone. I had left it on silent! Steve had called me to say that the diver had relocated onto F2. I had just about enough time to walk back along the causeway to see the diver and get back to my car before 17:00 when the reservoir closed. Armed with location instructions from Steve, I soon found the diver loafing some distance offshore and I rattled off a few record shots before returning to my car thoroughly satisfied by my day of winter birding.
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| Record shot of Great Northern Diver in the gloom |
OK it’s time to delve into the mysteries of the universe again so look away now if equations turned you an unpleasant shade of green at school!
I’ve mentioned before that there is something very fundamentally wrong with our current understanding of the universe. Firstly, the two corner stones of modern Physics, i.e. general relativity, and quantum mechanics, are incompatible. Secondly, and somewhat importantly for our understanding of the universe, we don’t know what most of it is made of! For the latter we have coined the term “dark matter” which might as well be named “we haven’t a clue what you are matter” Thirdly, our current theories say that the big bang should have produced equal amounts of matter and antimatter which should have annihilated leaving only energy behind, our existence is proof that this did not happen!
Quantum mechanics provides us with our current best understanding of all the various elementary particles in the universe via the so called Standard Model. The last missing piece of the Standard Model jigsaw was the Higgs Boson, the particle that gives many other particles mass, which was subsequently observed at the Large hadron Collider at CERN a few years back. However, we know for the reasons stated above, that the Standard Model is not complete. The LHC had two main aims, to find the Higgs Boson (tick) and to find new particles beyond those in the Standard Model to help us develop new more complete theories of nature.
Very excitingly, well at least for a nerdy physicist, recent experiments have hinted at new physics beyond the Standard Model which may elucidate the dark matter problem. We know of four fundamental forces of nature, two of which, gravity and electromagnetism, are very familiar to most people. The other two, the strong and weak nuclear forces, act over very short distances and hold nuclei together. The way that some elementary particles called quarks are decaying at LHC cannot be explained by the Standard Model and its becoming increasingly likely that a new, previous unknow, fifth force of nature is involved. As yet the evidence for this has not reached the stringent criteria particle physicists use to announce a discovery but there is now less than one in a thousand chance of this being erroneous. More experiments at LHC and other facilities will soon reach the threshold were a new, totally game changing discovery can be announced. Perhaps we will finally know what most of the universe is made of. For a more detail article on the probably fifth force click here.
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