20th May

A day of very birdable clear, sunny and increasingly warm conditions provided another good flurry of late migrants but looked to be fizzling out without any particular highlight when a classic Portland 'out of nowhere' mid-afternoon rarity - a Western Subalpine Warbler in this case - showed up in the Obs garden mist-nets. The majority of the morning passage involved visible migrants, with 136 House Martins, 85 Swallows, 84 Swifts and a Tree Pipit through at the Bill; a good many of the 30 or so Spotted Flycatchers logged around the south of the island were also active migrants that headed straight through overhead, whilst the likes of 3 Chiffchaffs, 2 Blackcaps and 2 Willow Warblers were new on the ground at the Bill and the 2 long-staying Corn Buntings there and at Barleycrates Lane were still about. Loitering Manx Shearwaters dominated offshore, where 27 Common Scoter, 5 Sandwich Terns, 3 Great Northern Divers and a Sanderling also passed by.

What with the Moltoni's Warbler only a little over a week ago and now today's apparent Western Subalpine Warbler it seems that some vector of Subalp vagrancy is headed toward Portland right now - not great for them but fun for us. In comparison to the Moltoni's what red there was on today's bird immediately struck as as orangey-toned and not in the least bit pink; it was also in pretty shoddy plumage whereas the Moltoni's was in really good order - with the tail pattern straight away having ruled out Eastern Subalpine, to our eyes these features strongly favoured Western Subalpine:

Although clearly not a fine male we were hesitant with sexing the bird - the literature urges caution so although the overall whiteness of the underparts seems to favour it being a female we're not sure that completely eliminates the possibility of it being a young male:

If we're interpreting the state of moult correctly then age-wise it's most likely a first-summer since there are three new outer primaries, two new inner secondaries and a new alula - all of which have been gained during the partial prebreeding moult in Africa (this moult is more extensive in young birds than it is in adults):

In typical Western Subalpine fashion there were multiple generations of tail feathers: it looks like the very worn central pair are old juvenile feathers, whereas the others are a mix of post-juvenile and prebreeding moult feathers © Martin Cade: