As good as it gets

The words needle and haystack come to mind.

No surprises for guessing the top priority on the to-do list today - correct, get the kids off to school in good order. Yes, while debate about gull identification continues apace, life goes on.

So I wasn't in position at Rainham until about 10.30am, and it was a good while after that, thanks to Harry Lacey, that I learned Richard Millington had seen the putative Slaty-backed Gull about two hours earlier, albeit very briefly. He must have had even less sleep than me last night. I managed to speak to Richard and he seemed pretty enthusiastic about it, but it's not for me to paraphrase his views - no doubt more will be written and said in due course.

Anyhow, the next report of the bird, from Wennington Marshes, was rather tentative at first, but then became more convincing, and I was pleased to get a call saying it was heading towards the landfill. Within 20 minutes I managed to relocate it among thousands of gulls, but by the time I had extracted my camera from its polythene wrapping (there was steady rain at this point) the bird decided to fly - towards me! It veered left, landed, almost got flattened by a truck and then flew again, alighting briefly.

I fired off several shots on the ground, and then more in flight as it departed - all 32 images are timed by the camera at 12:35, so that gives an idea of the brevity of its visit. I couldn't locate it again for another hour and four minutes, when I picked it out very distantly on the far side of the landfill. To cut a long story short, through regular mobile contact with Andy Tweed everyone present on the cycle track outside the landfill a short while later got to see it.

Time is running out tonight, so briefly here's a few images which I believe confirm my identification on first views yesterday as an adult Slaty-backed Gull (possibly a young adult, but more on that anon):

Up close, the bill shows a couple of fine dark markings near the tip which weren't visible in yesterday's field views. According to Olsen and Larsson (2003), some 25-30 per cent of winter adults show such markings. Note also the
head and bill profile and extent of the streaking, especially how it clusters around and behind the eye.
Photos and text © Dominic Mitchell - do not use without permission. Fees apply.

An enlargement to show the leg colour and also tibia length - in my opinion not as long as on Caspian Gull,
as claimed today. Caspians look 'leggy', not like this. Next to a Great Black-back, I felt it was shorter legged.
Photos and text © Dominic Mitchell - do not use without permission. Fees apply.

Pearl jam: note the so-called 'string of pearls' on the wing-tip, a character highly indicative of Slaty-backed Gull and shown to good effect here. The mirror on P10 is separated from the white feather tip by a narrow black band, a feature shown by about 20 per cent of adult Slaty-backs (C Gibbins pers comm). Note also the very broad white secondary tips.
Photos and text © Dominic Mitchell - do not use without permission. Fees apply.

Go compare: from left to right, Great Black-backed Gull, Slaty-backed Gull and argenteus Herring Gull. Notwithstanding size differences between male and female gulls, a useful comparison image.
Photos and text © Dominic Mitchell - do not use without permission. Fees apply.

There's much more to say about this bird, so I will shortly start preparing the coverage for the next (March) issue of Birdwatch - and it will include some additional images not featured here. In view of the fact that shots of the open wing-tip have now been obtained and also fit my original identification of Slaty-backed Gull, I will also be compiling a full description for submission as the first British record of that species. (Incidentally, it is certainly a different individual from the only previous Western Palearctic bird, which visited Latvia and Lithuania in 2009 - Chris Gibbins has confirmed that that bird had a broad white tip to P10).

UPDATE: Simon Buckell has kindly supplied with some footage he shot of the bird (see his excellent blog for more MPEG clips at http://shorebirder-waderworld.blogspot.com):

Finally, for now at least, my thanks to those who have taken an interest in this bird and discussed its ID with me in person and in the field, especially Martin Garner and Chris Gibbins, and also Andy Tweed and others at Rainham, David Callahan, Ian Lycett and more than I can name now; ID-Frontiers was, as always, a very helpful source of feedback. The management at Veolia Environmental Services have been especially patient, as have staff at Rainham Marshes RSPB - I hope would-be observers of this bird bear that in mind and follow the instructions below.

IMPORTANT - ACCESS AT RAINHAM
There are many thousands of gulls at Rainham at the moment, and they favour the RSPB reserve, the adjacent Wennington Marshes (very large numbers of loafing birds), the river/foreshore (partly tide dependent) and the tip (strictly out of bounds at all times; only working until 12 noon on Saturdays). If you are planning to look for the bird, it is essential to follow these instructions, provided this evening by the RSPB:

Parking options

• Rainham Marshes RSPB main car park, off New Tank Hill Road, RM19 1SZ. Park and walk along river wall to the west and then on the cycle path on the inland side towards the tip, stopping to scan Wennington Marshes on your right.
• Rainham Riverside car park off Coldharbour Lane. Only room for about 20 cars. Do not park in or obstruct entrance road or disabled spaces. If parking here walk back down the path to Coldharbour Lane and follow the cycle path east past the tip to Wennington and then Aveley Bay. Note: there was a break-in at this car park today, so be vigilant.

DO NOT UNDER ANY CIRCUMSTANCES PARK ON COLDHARBOUR LANE (OR EVEN ON THE VERGE): THIS IS HIGHLY DANGEROUS AND SECURITY WILL MOVE YOU ON.
DO NOT UNDER ANY CIRCUMSTANCES PARK IN THE WORKS CAR PARK FOR THE VEOLIA LANDFILL SITE OR THE INDUSTRIAL UNITS AT COLDHARBOUR POINT. SECURITY WILL CLAMP ALL UNAUTHORISED CARS.

Viewing options

• Scan the fields of Wennington Marshes, where all the gulls come down to rest during the day.
• Enter the reserve via the visitor centre and check Aveley Pools and the Target Pools, where gulls also come down to bathe.
• Check the foreshore to the east of the Stone Barges, accessed via the Rainham Riverside car park as birds also commute here to bathe.
• Check Aveley Bay for similar reasons.
• DO NOT ATTEMPT TO ACCESS THE LANDFILL SITE UNDER ANY CIRCUMSTANCES. It can be viewed more distantly from the cycle path, but the gulls are much easier to check on Wennington Marshes, where they linger for longer and are far less active. 

Request from the North Thames Gull Group
Writing on BirdForum, Paul Roper of the North Thames Gull Group said:

• Firstly please could every one attempting to see this bird be very mindful of the tip and the operators at Rainham, the private areas of land and the health and safety issues along Cold Harbour Lane. The North Thames Gull Group has spent a considerable number of years working on the landfill site here and at Pitsea and we rely on the good will of the tip operators to allow us to undertake our studies. I am not sure if anyone has informed the tip operators of the potential numbers of people and issues which may occur with large numbers of people in this area. I am undecided if I will attend in the morning myself and we were planning a cannon netting session on the tip which I have now cancelled.
• Secondly we have been colour ringing birds here for the last three winters and I would request any colour ring observations of Orange rings can be sent direct to me for information and reporting. As there are a large number of birders potentially attending in the morning I would suspect there will be some colour ringed birds present."