Rare Bird Alert weekly round-up: 24 - 30 October 2012

The week's highlights:
Sensational belated news from Dorset ~ Pale-legged or Sakhalin Leaf Warbler on Portland
Chestnut-eared Bunting shows well on Shetland
…while the Siberian Rubythroat doesn’t!
Bobolink and American Buff-bellied Pipit make for a Super Sunday on Shetland too….
Pied-billed Grebe makes it to Mayo
The Kilminning Eastern Olivaceous Warbler lingers in to another week
Juvenile female Northern Harrier continues to perform in Wexford
Scilly hangs on to an American Buff-bellied Pipit and there’s a Blackpoll Warbler too.

Short and sweet this week ~ the rarities just kept on coming through much of the week as various ripples of weather continued to pepper the country with a continuing northeasterly airflow that maintained fall conditions until almost the weekend.

The first blast of some truly Arctic air followed as seawatchers along the whole of the east coast donned the oil-skins to brave the cold and wet. As the review period drew to a close, sunny spells, southwesterlies and showers were the order of the day as many wondered “what’s next”.

Many birders though were still picking themselves off the floor after some mind-boggling news came through from the south coast……

Headline birds
Oh. My. Goodness. There have been some fairly amazing moments in these past four weeks of 2012 already ~ the Fair Isle Magnolia Warbler was one (a not entirely unexpected repeat, despite the 31 year wait). The wonderful discovery of the Eastern Kingbird off the Galway coast, on Inishmore was another (a long predicted vagrant finally making it over the Atlantic) while last week’s remarkable second showing of a wonderfully far-flung vagrant from the Eastern Palearctic, the Shetland Chestnut-eared Bunting, seemed to sound a suitably resounding farewell from the cream of the crop of the top-ranked rarities of the autumn.

How wrong was that!?!?!

It is really hard to believe that Chestnut-eared Bunting could ever play second fiddle to anything. If something was to topple such an extraordinary bird, it would truly have to be off the scale. A bird that would push back vagrancy boundaries. A bird that would turn the Spinal Tap amp up to 11…..

…well. It’s happened…

During the evening of 24th, news emerged of what may be the most extraordinary passerine vagrant of all time…..an extraordinary Phylloscopus warbler had been seen and photographed in a garden on the Isle of Portland during the afternoon of 22nd and it was one of two species….

Portland Bird Observatory warden Martin Cade takes up the story:

“Many birders will remember Pete and Debby Saunders’ garden at Southwell, Portland, from the Collared Flycatcher twitch in April 2009, and, with back-up rares of the quality of Yellow-breasted Bunting also on the garden list, it was no great surprise when they phoned to report two Yellow-browed Warblers in their sycamores on a day when Portland was awash with migrants.

Their next message though was a good deal more arresting: ‘Eastern Crowned Warbler in the garden!’ Debby explained that the unfamiliar phyllosc had appeared and they’d summoned Portland-resident, Grahame Walbridge, who was birding nearby, for help and he’d made the call. News was quickly released to a few local birders, who contented themselves with views of sorts as the bird darted about high in its chosen single sycamore. Towards evening it came lower and questions began to be asked, notably concerning the apparent lack of any trace of a crown stripe.

Sadly, at the time of discovery, general access wasn’t possible but, during the evening, once the photographs had been scrutinised and the bird’s true identity had been narrowed down to this notoriously tricky pair of species, an agreement was reached whereby the Observatory would attempt to trap the bird the following morning (23rd).

If successful, we were looking to relocate the bird to a site close-by which would allow more general viewing ~ unfortunately the bird didn’t play the game ~ it wasn’t present in the garden and it wasn’t seen during subsequent days.

With the bird only being observed in the field it seems highly likely that we will never be possible to identify the bird to species level ~ a critical in-hand examination would appear to be the only way to be certain of the bird’s absolute identity and make the call between Pale-legged Leaf Warbler and Sakhalin Leaf Warbler.

Paul Leader got in touch with us and, very kindly, commented on the images he had seen of the Portland bird. His initial thoughts, some of which are detailed below, slightly favoured Sakhalin Leaf Warbler.

“Plumage wise, there is nothing to choose as the two species are extremely similar”

“Structurally, the apparent relatively long primary projection may be a pro-SLW feature.”

“In terms of range, there is little to choose: although PLLW breeds further west (around 7100 km from Portland), the bulk of the breeding grounds are further east at 7400-8500 km away; Hokkaido/Sakhalin are approx. 8300-9100 km from Portland.”

“SLW is, on average, a later migrant in Hong Kong”

“On the breeding grounds, SLW is highly arboreal, singing in the canopy, whereas PLLW is generally a low-level skulker” (the Southwell bird spent most of its time relatively high up in a sycamore in a fashion not unlike Yellow-browed Warbler)".

Little is really known about Sakhalin Leaf Warbler ~ a two-line, 30 word statement is all that exists on Wikipedia (!) but the IUCN Red List of Threatened Species mentions that….

“The global population size has not been quantified, though national population estimates include: < c.50 individuals on migration in Korea;c.100-100,000 breeding pairs and c.50-10,000 individuals on migration in Japan and c.100-100,000 breeding pairs and c.50-10,000 individuals on migration in Russia (Brazil 2009).”

The population trend appears to be stable for the species and it does not approach the threshold for “Vulnerable” status ~ indeed it is listed as a species in the “Least Concern” category.

The same Red List states the following for Pale-legged Leaf Warbler….(43 words in the two line Wikipedia entry for this one…!)

“The global population size has not been quantified, but the species is reported to be quite common (Baker 1997), while national population estimates include: c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in China; possibly < c.50 individuals on migration in Taiwan; c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in Korea and c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Russia (Brazil 2009).”

As with Sakhalin Leaf Warbler, the population trend also appears to be stable for the species and it too does not approach the threshold for “Vulnerable” status ~ just as with Sakhalin Leaf Warbler, Pale-legged Leaf Warbler is listed as a species in the “Least Concern” category.

Sibley and Monroe state that tenellipes and borealoides are separable only by their territorial songs and calls and it would seem, from a swift trawl through online conversations from people who really know, that it may well be just the song that holds firm as the best way to separate the two (which were, for many years, lumped as one species, both tenellipes and borealoides falling under the Pale-legged Leaf Warbler umbrella).

Whilst discussing the new order of ultra-long-range vagrants last week this was mentioned….”we have been getting more and more birds from deep within the Eastern Palearctic in the last decade ~ Rufous-tailed Robin and Eastern Crowned Warbler” ~ well, we can now add something else to that list….whether it was Pale-legged or Sakhalin Leaf Warbler it is the most astonishing record and, in the decades to come, the past 10 years or so will be used to map out the beginning of a brand new phase of extraordinary vagrancy.

Leading on from this jaw-dropping record, and the other far-out, far eastern monster rarities of the last decade (the two Robins, the two Eastern Crowned Warblers, the two Chestnut-eared Buntings and now the brand new Phylloscopus) ~ could there be any implications for other older records of previous long-range potential vagrants.

Questions may be asked once more about the Sunk Island Mugimaki Flycatcher. Likewise the Fair Isle Chestnut Bunting (though presumably not the Norfolk one) and perhaps even one or two of the neat-looking Pallas’s Rosefinches and even the Norfolk Meadow Bunting (in the dunes at Hunstanton in early 1996 and, in early May 2001, along the track at Burnham Overy)….could any of these actually fall in to the required zone of acceptance now?

It seems unlikely, certainly for the latter two species, but the former two? Maybe, just maybe there’s a chance of an upgrade for them. Both Mugimaki Flycatcher and Chestnut Bunting fell short (just short in terms of the Fair Isle Chestnut Bunting ~ early September 2002) of the dates in which this new crop of Eastern Palearctic vagrants have occurred, but were any of the four species named above actually the fore-runners of the latest batch of vagrants?



Meanwhile much more of last week's news in the full round-up online including;
Bobolink on mainland Shetland
Siberian Rubythroat and Chestnut-eared Bunting remain on Shetland
Hornemann's Arctic Redpoll in Norfolk
Videos of Desert Wheatear in Worthing, Penduline Tit, Chough, Great White Egret and Little Bunting on Scilly
HD Waxwing video from Hugh Harrop of Shetland Wildlife

Plus much more...