|Male Eastern Subalpine Warbler, Walthamstow Marsh, Greater London, 15 May 1994. © Mike McDonnell|
In fact, I heard it first, and almost dismissed its rapid, puzzling song as some kind of Lesser Whitethroat sub-song. Thankfully, I stuck with it, and a few minutes later clinched London's second record of Subalpine Warbler. It stayed in the area for much of the day, and an estimated 200 people got to see it.
At the time, I submitted the record to the Rarities Committee simply as a Subalpine Warbler, and it was accepted as such. But with more recent interest in subspecific identification, especially since Hadoram Shirihai's landmark Sylvia Warblers tome in 2001, I thought it was time to look again at the bird. What's very obvious even in this scan of an old colour print is the limited extent of the brick-red throat and upper breast, leaving the rest of the underparts with just a wash of reddish - classic albistriata, the eastern subspecies (in nominate Western the colour extends fairly uniformly right across the lower underparts).
I solicited a couple of second opinions and sent out my notes and two photos of the bird (in the other it is less clear than here). Marc Duquet, Editor of the French journal Ornithos, has Western Subalpines breeding in his garden (wow!). He commented: "I think that [it fits] quite well with albistriata and in my opinion excludes Western Subalpine which never has a so dark and contrasting breast. Furthermore, the long and broad white moustache is also a good feature for albistriata." Andy Stoddart, who wrote the recent Subalpine Warbler ID feature for Birdwatch, also thought the images and notes "suggest a bird with the right colour hues and with the pinky colour restricted to the chin, throat and upper breast, leaving faintly washed flanks and an extensive white belly. Also the submoustachial stripe looks very long and broad. On this basis I’d be fairly comfortable with it being albistriata ...", along with an appropriate caveat about the Rarities Committee (which has so far only accepted about 36 records of albistriata - far lower than the real total).
There have now been four London Subalpine Warblers, including one in Barnes in 2003, and Johnny Allan kindly lent me his photo of the bird (below). This too is an Eastern, and Marc Duquet added: "The dark reddish throat colour is indicative of albistriata. The weaker white moustache and the reddish colour restricted to throat fit with a 2nd-cy (not an adult)."
|Male Eastern Subalpine Warbler, Lonsdale Road Reservoir, Greater London, April 2003. © Johnny Allan|
Thanks to Johnny Allan, Bob Arnfield, Roger Riddington, Marc Duquet and Andy Stoddart for their assistance in various ways, and also to the late Mike McDonnell, the only photographer to obtain images of the Walthamstow bird.