Tuesday, 27 November 2012

Something completely different ...

Name that gull - if you can.
... but what? When I first saw this gull at my regular study site the other day, I did a double take. The strikingly white wings and bicoloured bill made it look potentially exciting, if not downright exotic. Some second-winter beast from the Pacific, perhaps? Or perhaps not ... its plumage looks in decidedly poor condition, not just  those heavily worn wings, but also about the head. Some tell-tale pale grey feathers are also visible on the mantle. Almost immediately on finding the bird it flew off through the throng of feeding gulls, but soon after I relocated it in a loafing area, where it promptly went to sleep. The image below, taken just before it did so, reveals it to be a second-winter bird - I presume simply a very unhealthy European Herring Gull, although in this state it's hard to tell to be sure.

Another view showing the wings above and below, and the tail. Second-winter European Herring Gull, presumably?

Friday, 23 November 2012

Colour-ringed intermedius

First-calendar-year Lesser Black-backed Gull of the subspecies intermedius. This individual was ringed as a chick in north-east Denmark in June this year. Note the new first-winter mantle and scapular feathers.
Lesser Black-backed Gulls are a very familiar sight in London, where the subspecies graellsii has a small but increasing breeding population, with far larger numbers in winter. Smaller numbers of intermedius-type birds also occur outside the breeding season, and are best identified in adult plumage when their blackish upperparts stand out in contrast to the dark lead-grey of graellsii. Identifying intermedius at other ages is much trickier, if not sometimes impossible with complete certainty, and it has been suggested that the two subspecies may represent only one clinal taxon (Olsen and Larsson 2003).

I found the above first-winter Lesser Black-backed Gull on 16 November on the Thames at Rainham, and was immediately struck by its unusually pale head and underparts contrasting with darker upperparts. Only after I started photographing it did I realise it was sporting a smart blue colour ring. I've seen blue-ringed Lesser Black-backeds from the Low Countries here before so forwarded details to a scheme there, only to be told it was in fact a Danish ring.

V.MOL reveals a rather strongly barred rump and uppertail, among other features.
Thanks to a prompt response from Kjeld Tommy Pedersen, I now know that V.MOL was ringed as a chick on the Danish island of Hirsholm, in the Kattegat between Denmark and Sweden, on 26 June this year. Geographically this is close to the edge of the range of intermedius in southern Scandinavia; head south-east into the mouth of the Baltic from here and nominate fuscus ('Baltic Gull') takes over. This was not only my first colour-ringed Danish gull, but also welcome confirmation from a British perspective of the appearance of first-winter intermedius.

UPDATE Today (26 November) I found V.MOL again at the same site - remarkably among thousands of gulls in the area - and it was within 100 m of where I first saw it 10 days ago! It spooked quickly but I managed to fire off this shot to show the underwing pattern, something I wasn't able to observe last time.

Ten days later, here is colour-ringed intermedius V.MOL again, showing off the axillary and underwing pattern.
I've also created a Google map to show the distance between ringing and observation sites - 588 miles in this instance. I'll be plotting further colour-ringed Lesser Black-backed Gull sightings on this map in due course.

View Lesser Black-backed Gull in a larger map

Friday, 16 November 2012

Friday gulling

One of three Caspian Gulls today in the Rainham area.
Gull numbers are starting to build up nicely for the winter now, and I spent five hours working through them today on my local patch at Rainham Marshes. Visibility ranged from poor to abysmal, with fog hanging in the Thames corridor and failing to clear even by the afternoon. There were no major surprises, but I eventually managed to dig out three Caspian Gulls (the bird above/below, probably a fourth-winter, and two first-winters) and at least 15 Yellow-legged Gulls. I also checked colour many rings, and hope to report back in due course with some interesting results, including for a young intermedius-type Lesser Black-backed Gull which was wearing a continental ring. In the meantime, here are a few photos from the session.

First-winter Caspian Gull - one of two present this afternoon (the other individual being notably darker).
At least 15 Yellow-legged Gulls were present in the area, some already looking in breeding condition.
From left to right: adult or near-adult Yellow-legged, argenteus Herring and graellsii Lesser Black-backed Gulls.

Tuesday, 13 November 2012

White-rumped record-breakers!

Autumn 2012 will long be remembered in the Azores for the record-breaking influx of White-rumped Sandpipers. This flock roosting over high tide at Cabo da Praia, Terceira, on 19 October was part of a gathering of at least 180 present at the site - one of the largest single groups ever recorded in Europe (though numbers there peaked earlier at well over 200). It's not often that you see Sanderlings in Europe outnumbered by White-rumped Sandpipers, so enjoy!

Monday, 12 November 2012

Death by heron: the verdict

Grey Heron and its victim at Rainham Marshes RSPB. Did you try and identify it?
Thanks to all those who responded on the identity of the mystery bird being consumed by the Grey Heron in the previous post. Of the 13 responses received, the most popular choice was Black-necked Grebe (five votes), followed by Slavonian Grebe (two votes and another for Slavonian or Red-necked), Little Grebe (two votes), Eurasian Coot (one vote and one tentative) and Great Crested Grebe (one ‘probable’).

Looking again at the photos, in the first image we can get a feel for the overall body length of the bird in question: it seems very roughly equivalent to or a little shorter than the leg length of the heron (the feet of which obviously cannot be seen). Grey Heron’s tarsus (the leg below the knee) averages 151 mm in males and 141 mm in females, with an overall range of 132-172 mm (BWP). If the tarsus is about half the overall leg length, that gives a maximum range of 264-344 mm: this overall length fits well with Black-necked Grebe (280-340 mm) and overlaps with the lower end of Slavonian Grebe (310-380 mm) and the upper end of Little Grebe (230-290 mm). On this basis the two larger grebe species and Eurasian Coot can be excluded on size alone (as well as other characters).

The plumage also provides clues. In the first image the bird appears blackish above from head and neck right down over the upperparts. As pointed out in the comments, Slavonian and Black-necked differ in the ‘narrowness’ of the black line on the back of the head, but that is the case on swimming birds holding the head at right angles to the neck: in this image, with the head and neck held vertically in line by the heron, the feathering on the back of the head would be compressed into the neck and I don’t think any meaningful distinction would be visible.

The next three shots all show that the bird has clean white underparts, with no duskiness visible and a sharp division between white flanks and blackish upperparts. This fits better with Slavonian Grebe than with Black-necked, which has a tendency towards more extensive darkish ‘discolouring’ on the flanks. The whiteness of this area would seem to exclude Little Grebe, which in all plumages anyway appears more brown and buff. 

Slavonian (left) and Black-necked Grebes in non-breeding plumage: note the differences in the distribution of black and white on the head, neck and flanks.
If we accept that the likely choices are Slavonian or Black-necked Grebe, can we narrow it down further? Although it’s hard to see here, enlarging the first image in Photoshop seems to reveal a fairly well-demarcated black cap above whitish cheeks; certainly, the bird seems to lack the typical darkly smudged cheeks of Black-necked Grebe. This feature, together with the whiter flanks and underparts, strongly suggests to me that the bird is (or rather was) a Slavonian Grebe. This was my initial impression when I first downloaded the images and remains my tentative conclusion, but it does seem to me to fit best. Could a tired and lost ‘Slav’ have fallen victim to a predatory adult Grey Heron? Although Slavonian Grebe is rare in London, coincidentally one was also found the previous day elsewhere in the London area, at Thorpe Park. Perhaps we’ll never know for sure, but it’s been an interesting and educational episode.

Sunday, 11 November 2012

Death by heron

Having already coughed up its half-swallowed hapless victim, the adult Grey Heron repositions it for another attempt.
Though predominantly fish eaters, Grey Herons have a famously wide diet that extends from a wide range of aquatic creatures to small mammals, birds and plant material. I have previously watched one drown and consume a Brown Rat, which struck me as unusual at the time, but this latest episode - involving a waterbird almost too large to consume - is surely an even rarer event.

Getting the head and neck in is the easy bit - the body and legs are the problem.
I took this sequence of images two days ago at my local patch of Rainham RSPB, Greater London, over a period of about 15 minutes. They are from a much larger series which begins with the heron coughing up its partly swallowed prey because it seems simply too big to consume.

Almost there, but with the slow downward progress of 'lunch' the heron is starting to gag ...
I concentrated on getting the images at the time and assumed through the viewfinder that the victim was probably a Little Grebe. Looking more closely now, the detail suggests otherwise, with the bird having clean white flanks and blackish upperparts. What exactly it is, however, is open to speculation - comments welcome.

Wednesday, 7 November 2012

Lisbon lay-over

Black-headed Weaver seems to be thriving in the marshes of the Tejo Estuary near Lisbon.
With a morning flight from Terceira in the Azores to Lisbon but then a five-hour delay before the connection back to London Heathrow, I had some time in mainland Portugal crying out to be put to better use than the food hall of Terminal 1. And what better way of achieving that than hooking up with João Jara of local tour company Birds and Nature.

Lisbon is within a stone's throw of some great birding sites, notably the Tejo (or Tagus) Estuary, and it's hard to imagine anyone knowing them better than João. A former member of the Portuguese Rarities Committee whose time ended just before mine began, he greeted me with the news that he'd recently found Lesser Flamingo and American Golden Plover on the estuary. Our planned targets were rather more prosaic, with Black-headed Weaver and Yellow-crowned Bishop being two locally established - and therefore 'countable' - Category C species which are difficult (if not impossible) to see elsewhere in the Western Palearctic. But equally, I was also hoping for a quick fix of mainland Iberian birds.

Tuesday, 6 November 2012

Supporting local birding in the Azores

Participants at the event take a break for coffee during a fascinating programme of talks and discussions. 
My final visit to the Azores this year was a return to Terceira in early November to speak at the II Encontro de Observação de Aves dos Açores, a recently launched annual initiative aimed at driving interest and participation in the fledging Azorean birding scene and inspiring local people to get involved. Good numbers of birders from elsewhere in Europe visit some of the islands, at least in October, but anything to encourage local activity can only be good for birds and birding in the archipelago. My talk was about developing birding skills, while others discussed conservation projects, habitats, the endemic Monteiro's Storm-petrel, the occurrence of vagrants, and a range of other subjects.

Swedish birder Staffan Rodebrand from www.birdingazores.com talking about vagrancy patterns in the islands.
I met a few old faces but quite a few new ones too, and it was great to see the enthusiasm exhibited by some relative newcomers to birding - like Nelson Moura, for example, a young birder from Santa Maria with many good finds already to his credit. What the islands need is some kind of local society to bring all of these people together and provide a focus for their activities. But there are problems to overcome, not least logistical issues - like the fact that the nine islands of the Azores are spread out over 420,000 square miles, with half the population of quarter of a million inhabiting the main island of São Miguel (if you thought the archipelago was the Portuguese equivalent of Scilly, think again). Nor is it easy to buy books on birds or even binoculars, so nurturing any local interest is not easy either. Hopefully, this will change over time.

Talking birds in the Azores, from left: Gerbrand Michielsen, Menno van Duijn, Miguel Ferreira,
Helena Guimar
ães, Justin Hart and the Rodebrands.
Time in the field was inevitably limited, but even with just a few hours to spare it was great to spend more time enjoying some quality birds, including American Wigeon, Glossy Ibis, Semipalmated Plover, two each of Lesser Yellowlegs and Common Redshank (the latter rarer than the former here), and assorted gulls including at least two first-winter Mediterraneans. Is this last species now wintering regularly here, albeit in tiny numbers? One of many questions to ponder about Azorean birds, but in the meantime thanks to Gerbrand Michielsen and Ana Carvalho for the opportunity to be involved.


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