Net gains

This adult Mediterranean Gull landed very close to the ringing area. Interesting to note how the hood develops ...

... which is different to this second individual, another adult that I found as proceedings drew to a close.

Gull-watching is so often a solo activity at Rainham, and with the exception of Andy Tweed and a couple of the other regulars, there is rarely anyone else to chew the cud with. So yesterday morning it made a pleasant change to team up with the North Thames Gull Group for their ringing session on the landfill. The cannon-netting had already taken place by the time I got there, and Paul Roper and colleagues were beginning to process a catch of 411 gulls - more than half of them Herring (both argenteus and argentatus), plus four other species. Here's a few highlights, including Caspian and Yellow-legged Gulls, from a productive morning.

Big Garden Birdwatch pays off

Waxwing in the garden this morning: a first for my Big Garden Birdwatch efforts.

Having started taking part in the RSPB's Big Garden Birdwatch with the children when they were younger, I've maintained it as a late January tradition. This morning's count, from 8.10-9.10am, included almost all of the expected species, but with one notable addition: Waxwing! Just a single bird showed up in the timed period, though five were on view from the study window later in the morning.

This wintering male Blackcap, first seen in December, also put in a welcome appearance in the beech tree.

In order of appearance, here's the complete list of species and maximum numbers seen in/over the garden this morning - at 18 species, a one-hour record:

Redwing (1), Carrion Crow (2), Blue Tit (4), Blackbird (1), Great Tit (2), Black-headed Gull (3), Robin (1), Chaffinch (2), Magpie (3), Goldfinch (7), Starling (2), Woodpigeon (7), Blackcap (1 - male), Waxwing (1), Herring Gull (3), Jay (1), Feral Rock Dove (1), Kestrel (1).

Hate gulls? Look away now

Adult Caspian Gull at Rainham today, with argenteus Herring, graellsii Lesser Black-backed, Black-headed and Common Gulls. Note the head and bill profile, small dark eye, dull yellowish legs and general posture/jizz.

Wing-tip detail of the same bird as it flew. P10 has the classic extensively white tip shown by most adult Caspians, and P9 has a large white mirror across both webs. The black subterminal band on P5 is complete.

Bitter is not the word. My car told me it was between 1 and 2 degrees C on the way to Rainham this morning, but after standing in the open on the landfill in a stiff north-easterly for five hours, barely without moving, I can vouch that the wind chill factor made it considerably lower than freezing. So please humour me when I share this latest batch of gull shots - don't let me think I've lost several fingers and toes to frostbite in vain. Enough said - the pictures and captions can do the talking.

With its mustard-yellow bare-part coloration this adult gull suggests michahellis, albeit with a white-tipped P10 (rare in that species). Martin Garner and I have corresponded about it, and he has also consulted Chris Gibbins, who has looked at eastern michahellis a lot recently; they are happy this is a Caspian Gull, with the bright bare parts and size making it a male. Importantly, note the iris is pale - not dark, as wrongly claimed elsewhere - and the bill rather deep (compare with the other adult Caspian Gull above). A trap to watch out for in future ...

 The same bird as above - note the rather thick-necked jizz and heavy-looking bill of this individual.

 A crop of the same image, enlarged to show the pale iris and mustard-yellow, rather deep bill.

 Open wing-tip on the same bird. Note that black markings just extend to P4.

A sub-adult michahellis Yellow-legged Gull, with dark bill markings and black on the primary coverts.

First-winter Caspian Gull (centre) with first-winter Herring Gull (behind). A useful comparison shot: note the Caspian's whiter underparts, more solidly brown wing coverts, different scapular pattern, 'shawl' of hindneck streaking and bill and eye. This is a Polish-ringed bird, 65P6, ringed in May 2010 in Upper Silesia.

The same first-winter Caspian, this time showing the upperwing and underwing patterns, and tail.

One for the road: a monster adult or near-adult argentatus Herring Gull. This taxon is common at Rainham.
Below: click the 'play' button for a movie clip of today's adult Mediterranean Gull.

Day of the Bombycillids

Waxwings photographed from the bedroom window earlier this week. I doubt there will ever be another winter like this for this irruptive but usually rare species - at least not in my lifetime.

It sounds like a Fifties B-movie, doesn't it? But today was very much one for Bombycilla garrulus, and indeed it was the best locally so far this winter.

After a single bird flew past the window at home this morning, I decided to drive to work via Grove Avenue, Muswell Hill N10, where I first found a flock of birds about 12 days ago. I saw only 14 there yesterday lunchtime, but later in the afternoon my brother Auk had 120+ (a great result, as he hasn't birded properly for about three decades, but still secretly hankered after Waxwings). This morning, the flock had grown to a massive 285 - a figure that would have been a London record two months ago, and possibly still could be if I had been able to keep track of sightings. They made quite a sight flying down to feed on berries just north of the junction with Lansdowne Road, but were quite mobile.

Flushed with that success, I continued on to work, but just before turning off Western Road N22 into the car park at the Birdwatch office, caught sight of another 100 Waxwings feeding on sycamore buds along the railway line! These are probably the birds first seen in the same trees by David Callahan and Ian Lycett on Monday, but I strongly suspect they are a different flock to the Muswell Hill gathering. Allowing for unseen birds feeding in gardens near Grove Avenue (I could see some birds disappearing from view behind the houses), there may easily have been 400+ Waxwings to the north and east of Alexandra Park this morning.

I didn't have a camera with me today, so instead enjoy this shot of a group of Waxwings which appeared outside my bedroom window on Monday. I never tire of seeing them or photographing them (this shot was taken with my new Canon EOS 7D, which has performed impressively so far, and seems to auto-expose more accurately than the 50D).

Waxwings for lunch!

Our local flock of Waxwings, seen in this shot taken from the house, now numbers at least 145 birds.

Sunday lunch at home was rudely interrupted today by the sound of multiple trills coming from the garden. On looking out of the window I could see rows of Waxwings lining the beech tree and an adjacent birch and TV aerials, so I shot upstairs to the study and took this quick shot with my Canon G10. There were at least 145 birds, which as far as I'm aware is the biggest local flock on record.

Earlier today I'd already seen a group two roads away which numbered 36 soon after 9 am, but had risen to 50+ by 12.30pm. I assume several local parties had banded together to put on this amazing lunchtime display - they've gone for now but I'll head out with the camera later and try and get some proper shots. UPDATE: no sign of the flock later in the day, so here are a couple of shots from when I first found them exactly a week ago in nearby roads, and also a sample video clip shot with my new Canon EOS 7D:

The Waxwings found a handy blocked gutter in which to drink and bathe when they had finished stripping berries.

The flock were sometimes nervy, closing ranks on TV aerials when disturbed from their berry bushes.

Tip top

This second-winter Yellow-legged Gull was one of eight on the landfill site during the latest sesstion.

A good day for recording colour rings, with 15 Herring Gulls (mostly local birds) photographed and logged.

This Herring Gull, UR8T, was ringed at Pitsea, Essex, on 6 March 2010 and seen again on 6 August 2010 at St Maartenszee, Noord-Holland, Netherlands, before reappearing on the Thames at Rainham last Friday.

Another day passes, and still no sign of the Slaty-backed Gull. I put in a good six hours at Rainham on Friday, and estimated from my elevated position that at one time somewhere upwards of 10,000 gulls were on view on the landfill, Wennington and the reserve. Black-headed and Herring accounted for the majority, but there were large numbers of Common Gulls one the tip as well and Lesser Black-backeds seemed numerous too. Great Black-backeds probably numbered 200+ but I didn't make any counts other than Yellow-legged Gull (eight) and Caspian (just a single first-winter), focusing instead on trying to dig out the Slaty-backed and anything else that looked interesting.

Down in the dump

Third-calendar-year Yellow-legged Gull - one of 14 logged during the day.

The same Yellow-legged Gull on the deck with Black-headed Gulls - a smart plumage for a large gull at this age.

Good photographic opportunities: an adult Yellow-legged Gull reveals its wing-tip pattern while feeding.

More musings on Slaty-backed Gull

Another shot of last week's putative Slaty-backed Gull at Rainham, showing key details of the wing-tip pattern.
Photo and text © Dominic Mitchell - do not use without permission. Fees apply.

After two days on my patch I wasn’t back at Rainham over the weekend, but apparently more than 1,200 birders turned up on the Saturday hoping to see the Slaty-backed Gull. There was no mass sighting, however, even though the tip was working in the morning – I felt sure it was going to put in a reappearance. I’ll be looking for the bird again later this week but, in the meantime, I’ve been liaising with others who have had experience of the species, both in its native range and in the context of extralimital vagrants.

Head comparison of birds from Rainham (left) and Newfoundland (right). Note the close similarity in the extent and patterning of streaking, which in both individuals covers the entire head and most of the neck; the streaking is more concentrated around the eye, where it forms a short line running backwards, and both birds also show a diffuse darker patch at the rear corner of the ear coverts. The bill patterns of these birds also have similarities, being a very washed-out yellow from base to gonys, and then much brighter yellow to the tip. According to Olsen and Larsson 2003 darker eyes occur in 30 per cent of birds.
Photos © Dominic Mitchell (left) and Jared Clarke (right) - do not use without permission. Fees apply.

Osao and Michiaki Ujihara are renowned for their first-hand knowledge of Japanese gulls, and have established an excellent online image resource (see below). From their extensive experience they have provided expert opinion on numerous extralimital birds, so I asked for comments on the Rainham individual. I was pleased to hear that, like me, they felt it was a Slaty-backed Gull, saying they “can't find any wrong feature. Its overall appearance including the short-winged structure, wide tertial crescent, moderately dark mantle shade and ‘string of pearls’ look very nice. What a great find!”.

Slaty-backed Gull (foreground) with American Herring Gulls (right) and Great Black-backed Gull (behind), Connecticut, USA, 21 November 2008. A useful comparison of mantle shades.
Photo © Mark S Szantyr - do not use without permission. Fees apply.

The comment on the tone of the mantle is interesting, given that this has been cited as potentially problematic. This is nothing new, the same issue having been discussed at length on vagrant birds in both Connecticut (see above) and Newfoundland. On the former, the Ujiharas have previously commented: “In our experience, mantles of Slaty-backed Gulls are not as dark as American birders often expect”. There is clearly variation from more blackish birds to greyer individuals, and this is borne out by the range of Kodak grey scale values quoted in Howell and Dunn 2007, compared here with the two black-backed species:

• Lesser Black-backed Gull (subspecies L f graellsii): 9-11
• Slaty-backed Gull: 9.5-11.5
• Great Black-backed Gull: 13-15

Note how Slaty-backed overlaps extensively with graellsii Lesser Black-backed Gull, but not at all with Great Black-backed. Here are a few images which help illustrate this extensive variation (reproduced with permission from the photographers, to whom many thanks):

Slaty-backed Gull (foreground, with Glaucous-winged Gull), Juneau, Alaska, 17 January 2011. This stop-press image of a bird found yesterday was sent in overnight by Gus van Liet, and to my eye shows upperparts recalling graellsii Lesser Black-backed Gull in tone. This also seems to be a fairly dark-eyed (for SBGU) individual.
Photo © Nick Hajdukovich - do not use without permission. Fees apply.

Slaty-backed Gull, Kuril Islands, Russia, 6 June 2010. Even allowing for photographic vagaries, a very pale bird.
Photo © Dick Newell - do not use without permission. Fees apply.

Slaty-backed Gull, Japan, 24 February 2010. An obviously darker individual, with prominent underwing 'shadow'.
Photo © Ian Lycett - do not use without permission. Fees apply.

Slaty-backed Gull, Newfoundland, 13 January 2008. Same bird as in the head comparison montage above.
Photo © Jared Clarke - do not use without permission. Fees apply.

Slaty-backed Gull, Japan, 28 February 2008. The black bill band is almost the only remaining sign of immaturity.
Photo © James Lidster - do not use without permission. Fees apply.

Jared Clarke, who has good field experience of vagrant Slaty-backed Gulls in Newfoundland (having seen 14 out of 16 individuals), commented on the Rainham gull as follows: "I think your bird is a pure SBGU since all other features (with the exception of the slightly pale mantle) are dead-on and show no indication of a hybrid. I agree whole-heartedly with Nick Bonomo's recent comments [on ID-Frontiers] on this issue, and that unless there is more evidence of mixed blood than just the pale mantle (with some very experienced people saying that it is within range) than the best conclusion is a solid Slaty-backed Gull. Case closed."

A feature also mentioned as a possible pitfall for the Rainham bird is the underside of the ‘hand’, the dark show-through being less prominent than expected. While this may partly be affected by camera exposure, I suspect it could possibly also be related to the intensity of pigmentation on the upperparts. An accepted vagrant Slaty-backed from Connecticut shows a similar pattern (see this instructive image on James P Smith’s excellent blog).

Enough for now, save a few links for those still interested:

• For a Japanese bird which somewhat recalls the Rainham individual, see the fourth image down on this page on the Ujiharas’ excellent website.
• Mark S Szantyr has a great selection of shots of a Connecticut vagrant on his website .
• Steve Huggins has a nice darker, lemon-eyed bird here.

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."

A candidate Slaty-backed Gull - in London!

Adult gull at Rainham Marshes this afternoon showing characters of Slaty-backed Gull. 
Photos and text © Dominic Mitchell - do not use without permission. Fees apply.

I would like to have posted this news earlier today, but it's been one of those days ...

I paid a short visit to Rainham Marshes today, originally with the intention of trying out a new camera. However, when I got to the site there were so many gulls present that I decided to focus on gulling, so left the scope on the tripod and instead slung my trusty old 50D, 500mm f4 lens and 1.4x extender over my shoulder, foregoing using the new body while doing some serious birding.

Having worked through the gulls in the Coldharbour Lane area for about an hour and failed to find any Caspians and just a single Yellow-legged Gull, an adult, I began to wonder if the session would pay off. Bar a couple of interesting-looking Herring Gulls there seemed little else worthy of scrutiny. I was panning back through the massed ranks for about the eighth time when I stopped dead in my tracks. My gaze fixed on a large, dark-mantled gull that was immediately distinctive, and instantly I said to myself "adult Slaty-backed Gull!" Then I suspended belief in what I was thinking and looked at it again, feeling I must be kidding myself - yet, to my eyes at least, it still seemed to scream 'Slaty-back!'.

As I started to look at it more closely, another gull dropped in to land almost on top of it, flushing the bird. I panicked, reaching for the camera while trying to keep an eye on the bird. Fortunately, it came back down only a few metres away, so in case it flew again I fired off a short series of record shots (unfortunately, and unavoidably, directly through chain-link fencing, so they are not as clear, sharp and bright as the bird was 'in life'; they are all similar to the best two in the series, published here).

Note relative size and upperpart coloration of bird (left) compared to nearby Herring and Great Black-backed Gulls.
Photos and text © Dominic Mitchell - do not use without permission. Fees apply.

Here is a summary transcription of the points I noted at the time (please note this is not a full write-up, submission or discussion):

Size: almost size of nearby Great Black-backeds (possibly larger than one individual), and clearly significantly larger than Lesser Black-backed Gull and 'typical' argenteus Herring Gull. One nearby argentatus of similar size (all these taxa present in numbers in close proximity today).

Structure: bulky and solid, though different in 'character' to Great Black-backed Gull. Head less 'powerful' than the latter, more like Herring Gull, and in profile appeared more pot-bellied and a little shorter legged than Great Black-back.

Plumage: the combination of slaty-grey upperparts with very broad white tertial/secondary edges was immediately distinctive, especially taken in combination with the pink legs and large size. These broad white edges then continued, more narrowly but still conspicuously, along the folded edge of the wing. The upperparts were uniformly and solidly grey, with no trace of browner remnant immature markings; if anything, there was the slightest bluish tone to the upperparts, very subtly distinct from graellsii Lesser Black-back (this feature being mentioned to several others in discussion of the bird). The primaries were black, with four conspicuous white tips visible beyond the tertials at rest. The tail was white. The head and neck were diffusely and extensively streaked pale brown, these streaks combining to form a hood which extended at the front to the breast, becoming less boldy marked in this area. Streaking was densest around and especially below the eye. The rest of the underparts were unsullied white.

Bare parts: iris seemed pale yellow. Bill dull yellowish, dullest and more colourless towards base, brightening towards tip, and with small red spot near tip of lower mandible; not especially bulbous at the gonys. Legs shorter than nearby Great Black-back and pink, rather stronger in tone and darker than they appear in these 'uncontrasty' images - while watching through the scope, at times they seemed almost bubblegum-pink.

After watching the bird and noting the above points, I started to ring some local birders in a bid to get others to see it. While I was on the first call, still watching the gull through the scope one-handed, it took off and seemed to fly towards Wennington Marshes. In the very brief moment between when it took flight and when I lost it, I was unable to note detail on the underwing and wing-tip, as it was quickly hidden in a flurry of wings.

Eventually, three other observers joined me to help try and refind the bird, which we failed to do before dark. I remained reasonably happy that it was probably a Slaty-backed Gull, a species I have seen in Asia previously (though not for about nine years), but as always with large gulls, caution must be exercised. On seeing one of the other observers' copy of Howell and Dunn 2007, I was surprised that some adult-type Slaty-backeds can look almost black above, and that fact caused me some concern as this bird was closer in tone to graellsii Lesser Black-backed Gull (if anything, the grey appears subtly lighter in these images than some graellsii, but the quality of the images may also have affected this slightly).

I therefore welcome opinions on this bird, whatever its true identity - please leave your comments below. In the meantime, there is much research to do on this in the days ahead.

Postscript
Thanks to those who have taken the time to discuss this bird during the course of the evening. Early feedback, including from Martin Garner and others, is encouraging towards the identification of what would be the first British record of this species. The next thing to do is refind it, observe the open wing and hopefully photograph it. Having been slightly concerned initially about the upperpart tone, I have this evening checked Olsen and Larsson 2003 and other references, and also discussed the bird with Chris Gibbins (who found the Western Palearctic's first individual in Latvia two years ago), and it seems that the Rainham bird is unproblematic in this respect, falling within the likely variation for Slaty-backed Gull. But more comments have been solicited from other gull experts and online to try and gain a full range of opinion.

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). 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.

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.

Ducks redux: Aythyas and hybrids

Adult male Common Pochard (Alexandra Park, Greater London, 17 February 2008).

Adult female Common Pochard (Alexandra Park, Greater London, 7 September 2009).

I’ve been meaning to revisit the subject of Aythyas for a while, and have finally been prompted to do so as hybrids and the genuine article have become something of a talking point in recent days.

I don’t know what the level of incidence of hybridisation is between different Aythya species, but having found two hybrids in a small mixed flock of about 35 Tufted Ducks and Common Pochards on my patch last month, it is a question worth considering. In this instance statistics don’t tell the full story, as the photos below show - these two lookalike (and potentially related?) birds are not Tufted Duck x Pochard hybrid spawn.

Aythya hybrid 1 (Alexandra Park, Greater London, 19 December 2010).

The structure of this bird instantly recalls Pochard/Ferruginous Duck, as do elements of the plumage ...

Aythya hybrid 2 (Alexandra Park, Greater London, 19 December 2010).

The second bird is very similar to the first, though possibly a little less contrasting. In case you were about to ask, here’s a pukka adult female Ferruginous Duck for comparison:

Adult female Ferruginous Duck (Burgess Park, Greater London, 28 November 2010). Note the uniform plumage.

In view of the head/bill profile, plumage details and other characters of the two hybrids, my feeling was that they were Common Pochard x Ferruginous Duck hybrids (surely not interbreeding anywhere near London?). Keith Vinicombe has far more experience with hybrid Aythyas than me, so I asked him for his opinion. He replied: “I'd say that the hybrids look like juveniles and that Pochard must have been one of the parents, given the ‘Pochard grey’ shading on the scapulars and flanks plus the extensive black at the tip of the bill. The bottom bird also has a dull red eye, which would also indicate that (a) it is a juvenile male and (b) that one of its parents was a Pochard. (The top one also seems to have a reddish eye too). The black ground colour to the upperparts would suggest Tufted or Ferruginous as the other parent, while I would have said that the reddish brown breast would be indicative of Ferruginous. The lack of any tuft would not favour Tufted as a parent. Overall, I would guess that they are Pochard x Ferruginous, but at the Pochard end of the hybrid spectrum.”

Tufted Duck x Common Pochard hybrid recalling Lesser Scaup (Alexandra Park, Greater London, March 2010).

These are not the only Aythya hybrids seen in Alexandra Park in 2010. The above bird, of the more classic ‘Lesser Scaup’ type, appeared back in March last year. A rather smart individual, it has tried its best, even down to the purple head sheen. But its head shape, darker grey upperparts and extensively black nail on the bill are among the characters pointing to a male Tufted x female Common Pochard hybrid. Here’s a real drake Lesser Scaup, by way of comparison (excuse the poor quality slide scan):

Firt-winter drake Lesser Scaup (Regent's Park, Greater London, March 2003).

The next bird is not a hybrid either. Present among a gathering of Tufties and other ducks, this first-winter female Lesser Scaup showed well when I was visiting Caerlaverock WWT, Dumfries and Galloway, back in February 2006. The head shape is subtly different to Tufted Duck, as in fact is the whole profile (NB do Lesser Scaups seem to sit higher on the water?), but flank/mantle pattern/colour, bill markings and smaller size also separate the two (as would, if visible, its less extensively white wing-bar, which unlike Tufted Duck and Greater Scaup is greyer on the primaries).

First-winter female Lesser Scaup (Caerlaverock WWT, Dumfries and Galloway, 15 February 2006). The tell-tale
vermiculations are beginning to emerge. Jizz-wise, it is quite distinct in both shape and posture on the water.

Here is the same first-winter female Lesser Scaup (left), with a lookalike Tufted Duck for comparison. The bill
pattern and more solidly dark upperpart coloration of the latter are among the clues to its true identity.

Back to Common Pochard x Ferruginous Duck hybrids, these links might be of interest:

• A bird in Berkshire thought probably to be Ferruginous Duck x Pochard 
• Another Ferruginous-type wannabe in the same county
• This bird is much more like a Ferruginous
• Another Ferruginous x Pochard hybrid, this time from Switzerland
• … another from Italy …
• … and then video of one in France
• Finally, Nigel Milbourne has a few grotty Aythyas depicted on his Blagdon Lake website

Five-raptor day (updated!)

One of at least 10 Marsh Harriers at Capel Fleet, Isle of Sheppey, today.

I woke up very early today (too early, really), so decided to break with tradition and head down to the North Kent Marshes. Glad I did, as it's been a while since I've had six raptor species in a day in Britain. First up was a Eurasian Sparrowhawk across the road as soon as I came down off the bridge onto the island. This was followed by the first of at least 10 Marsh Harriers in the Capel Fleet/Harty Marshes area - though getting close enough for decent images proved difficult.

Another Marsh Harrier. Harty Marshes is a good area to study variation in this species' plumages.

While watching one of these a Merlin tore through a flock of Linnets, scattering birds everywhere. It was too quick to see whether it actually caught anything, but an impressive sight nonetheless. A Eurasian Kestrel in the same area was less dramatic, choosing to hunt from wires and also on the ground.

Linnets (or, in Merlin language, brunch).

After a while, having seen little else but a few waders, I headed up farther along the road towards Harty Ferry before retracing my route, now with the light behind me. As I glanced out to the right a very distant herd of swans caught my attention, so I returned to the raptor watchpoint and got out my scope and camera to check from the high ground. They proved just to be Mutes, but as I was scanning the background I picked up an even more distant raptor perched on a pile of hay bales. Zooming in to confirm it was a Common Buzzard, the bird was suddenly flushed by another buteo which clearly had a darker belly.

Buzzard, but which one? The dark chocolate belly and tail pattern led me to think this was originally a Rough-legged Buzzard, but thanks to comments received it appears it is a well-known local Common Buzzard.

The carpal patches on this bird are not that well marked - a feature to which I should originally have paid more heed.

I swapped the scope for my 500mm lens and converter, during which time the buteo moved to a nearby bush. As I started shooting it flew off east towards a fencepost where the Common Buzzard had taken up position, again displacing its congener.

These record shots were taken with a 500mm lens, 1.4x converter and 1.6x crop factor - effectively 22x magnification. In this shot the Buteo looks at its most Rough-leg-like.

The indistinct trailing edge to the underside of the wings suggests this bird is a juvenile.

By this time, even through the camera's viewfinder at such a distance, I'd seen enough to convince myself it was a Rough-legged Buzzard - a complete surprise, albeit a species which favours these marshes most years. However, it subsequently transpires the bird is actually a Common Buzzard, albeit one that seems to recall Rough-legged Buzzard in certain respects. Thanks to Rob Clements, Marc Giroud and an anonymous correspondent for pointing this out - I think some more field experience with Rough-legs would be good!

Corn Buntings still occur in good numbers on Sheppey - these birds were in a flock of 20 at Capel Fleet.

With c40 White-fronted Geese, 12 Red-legged Partridges, 100+ European Golden Plover, three Ruff, a Green Sandpiper and a flock of 20 Corn Buntings, it proved to be an excellent session. And with United beating Liverpool 1-0 in the FA Cup this afternoon, what more could you want?