I had the day off today, but ignored the temptation to travel north to Shetland for the Tengmalm's and instead did the usual tour of the regular East London sites.
It was pretty foggy early on and I couldn't even see the river when I arrived at the stone barges car park at Rainham, so headed back west to Creekmouth. Although the fog lingered for much of my visit here, it was fairly mild and around 10 Chiffchaffs were seen, though there wasn't anything among the gulls at the sewage works and outfall.
With the fog starting to clear by mid-morning I headed back to Rainham, where I soon picked up the juvenile Glaucous Gull floating around over the tip. Most of the gulls were going down to bathe on the river by the barges, so I headed up there. Viewing conditions were actually pretty good and it didn't take long for the 3cy Glaucous to put in an appearance, as well as a 2cy Yellow-legged Gull.
By late morning the haze was worsening and the temperature rocketing, so I headed back to the car and round to Erith Pier. Erith seems to be more of a weekend site, although gull numbers do vary with each visit. It was pretty quiet again today on the rising tide, with the six loaves dispatched into the Thames luring in very little. I'm still living in hope that the Bonaparte's might reappear, but it seems pretty unlikely now ... anyway, with nothing on show, it seemed churlish to ignore the fantastic light opportunities and I rattled off a few images of the Herring and Common Gulls drawn to the melee. I also saw the leucistic Herring Gull very distantly on the river towards the stone barges.
After establishing that Erith wasn't on song I made the short journey east to Crossness. A Eurasian Penduline Tit has been seen regularly this week, after initially being found back in November. It was showing on arrival, but was a bit distant for images ... although did eventually come closer, if only for a minute or so, before flying off out of view. It was nice to hear it both calling and (briefly) singing!
With the sun beginning to dip, I turned my attention back to gulls and headed for Princess Alice Way, Thamesmead. The tide was right up, and the customary wholemeal offerings soon brought in the usual handful of gulls. Given how few Herring and Lesser Black-backs are usually here, this spot has had a fantastic strike-rate with Yellow-legged Gull this winter and today's visit produced a new first-winter that I hadn't seen previously.
Where do you draw the line between one species and another? That is so often the burning question when it comes to large white-headed gulls.
Not only does each species tend to show great intraspecific variation in its physical characteristics, but species also routinely hybridise, further clouding the issue and eroding the recognised parameters between defined taxa. Perhaps the most recognisable example of a so-called 'hybrid swarm' among Palearctic gull-watchers is the Iceland-Kumlien's-Thayer's 'spectrum' breeding across Greenland and Arctic Canada. Of course, these are now apparently to be considered as one and the same species, but it was nonetheless a fine example of how a man-made scale, assessed on the basis of quantifying several physical features, was – rightly or wrongly – used to attach a label to any gull in question within the complex.
To some degree, the same 'problem' is rife in Central Europe. In parts of eastern Germany and Poland, and indeed to a lesser extent elsewhere, Caspian Gull has, on its westward march, come into routine contact with European Herring Gull, which itself has spread inland in recent decades. These two species seem to have no qualms about breeding with each other, as the numerous mixed colonies testify, and hybridisation between the two is very well documented through intensive studies by dedicated researchers, including long-standing ringing schemes.
Whether it's a case of increasing observer awareness or a genuine upturn in the frequency and number of hybrid pairs – or, more likely, a mixture of the two – birds exhibiting mixed characteristics seem to be on the increase in Britain. These birds show any number or combination of features of both parents, both in terms of plumage and structure. Perhaps I'm too critical with my Casps these days, but it seems to me that I'm seeing more and more of these 'unimpressive' birds – albeit a longer-term assessment of well-photographed individuals is probably sensible before leaping to surefire conclusions.
This was illustrated pretty well by the weekend's Thames gulling. On Saturday, I had a rather nice-looking first-winter Casp at Princess Alice Way, Thamesmead. It transpired that this bird, with its particularly distinctive look to the face, had been seen by Jamie and Dante at Crayford back on 31 December, but not since (Dante recognised it immediately). OK, no moulted coverts and perhaps a slightly mucky underwing, but plumage otherwise absolutely spot on for a textbook first-winter Casp.
Sunday, however, was enlivened by a couple of troublesome birds, one of which I have subsequently described more than once as a "horror show". It is perhaps no surprise that both bear German rings, to the point that Rich actually said of the first (X21A), "I bet that has a yellow ring on it" before it revealed its legs. Sure enough, it did. In terms of plumage, though, X21A – seen at Erith Pier – was the better of the two. Apart from its well-marked greater coverts, it otherwise looked fine, but structurally lacked Casp qualities in many poses. It was quite vocal, and sounded like a typical Caspian Gull.
However, if you thought X21A was bad ... then allow me introduce you to X90A. From the same colony as the above, this confusing mess of a Larus again sounds like a classic Caspian Gull, with the hoarse call often announced as this bird throws its weight arounds. And, at many angles, looks good for a cachinnans, with its rangy structure and various plumage features looking fine. But just take a look at those greater coverts, the extensive inner primary window, the well-marked tertials, the Herring-like scapulars, the comparatively uniform (and extensively pale-fringed) upperwing, the streaked head, the tail pattern ... suddenly you realise things aren't exactly looking great for a pure Casp. And, when you see it on the deck, it's enough to make you have nightmares.
X90A has been seen a Thamesmead twice and was also noted off Erith Pier in January, so it seems to have taken a liking to the Thames – perhaps we'll get the chance to see it develop in the coming months and years, as it'd be fascinating to see what it ends up looking like as a mature bird.
Sightings from the weekend otherwise included the usual mix of Yellow-legged Gulls, including this cracking adult against a typical Thames background at King Henry's Wharf, Woolwich. You don't see too many adults in winter, so always nice.
I had to pop up to Lincolnshire at the back end of the week, which gave me a small window to get some local birding in. Although I'm sure the cold snap probably helped a bit, I came back to London really enthused by winter birding in the area – it's only when you get back to the murky grey streets of the capital, where gulls are the primary order of the day, that you truly appreciate the wider avian opportunities of the Cambridgeshire and Lincolnshire fenlands.
That said, I nonetheless tried the gulls at Tanholt first thing on Friday. Actually it was overwhelmingly disappointing for larids, with large gull numbers low at the landfill site, where there wasn't much tipping activity going on. However the Hooded Crow was showing on arrival, although it dropped out of view before I could get my 'scope on it and it was only about 45 minutes later that it popped back up. Quite a smart bird really.
A quick zip around the Deepings area brought good birds at all sites visited. Deeping Lakes must now be the 'best' (at least most reliable) Long-eared Owl roost in the country, with five birds showing on the island on the main lake during my visit. Subsequently, six have been counted. It's come a long way since these were intermittent visitors to the nearby 'Gulley' area, although we have found nests of the species here in the past.
Deeping High Bank was also alive with birds, with upwards of 30 Goosanders along the Welland itself and a couple of separate flocks of Whooper Swans amassing to around 25 birds. I was happy to find a family of five Bewick's (the three juveniles were particularly pleasing) towards Deeping St Nicholas, while another 'family' (an adult and a juvenile) had arrived by Saturday. Marsh Harriers are also an ever-present fixture over the fields here these days and a Pink-footed Goose was with Mute Swans on the Friday.
My old patch at Baston & Langtoft Pits always has a few birds of interest, and a couple of visits on Friday and SAturday produced an adult Bewick's and up to a dozen Whooper Swans – the former being the first I've seen here since the big freeze in 2009/10. Even better still was a flock of 15 Eurasian White-fronted Geese, which looked pretty epic feeding among the wild swans on the frosted fen.