Ibericus or collybita?

So here it is then, for a bit of fun, my comparison of two chiffchaffs, one at Higher Penwortham in Lancashire, the other at Telford, Shropshire. Both were originally identified as possible Iberian chiffchaffs Phylloscopus ibericus, but seemingly only one bird, the Telford individual, has passed the test and is now generally accepted as an Iberian chiffchaff, with the Lancashire bird now consigned to the status of  an atypical common chiffchaff, P.collybita.

I went to see the Lancashire bird on Sunday evening in relatively dull conditions and a moderate breeze, and I saw the Shropshire bird on Tuesday in sunny conditions and a light breeze.

The song and the call are the two most important ways of separating the species. Here I'm going to concentrate on the song, but the call is just as important, with P.ibericus having a down-slurred 'wee-uu' as opposed to the instantly recognisable 'hweet' of P.collybita.

A typical P.ibericus has a song which is completely different to the familiar 'chiff-chaff' song of a typical P.collybita.  However the song of both species can be variable and a small number of P.collybita sing in a way which in the field can appear quite similar to P.ibericus. In such cases a recording and a sonogram of the song might be the only conclusive way of separating them. Here are the songs and sonograms of the Lancashire and Telford birds. I've included two recordings of the Lancashire bird because both are a bit too brief:




So far as I know, the sonograms are conclusive. Based on analysis of the sonograms, the Lancashire bird is P.collybita, the Telford bird is P.ibericus. End of story. Probably....

This is the Lancashire bird, photographed on a dull evening. The supercillium is not as distinct as it should be for P.ibericus, but there is a supercillium. There is only a faint eyestripe, it should be stronger in P.ibericus, but again the eyestripe is present. Notice the yellow in the supercillium, especially in front of the eye. This is a feature of P.ibericus. The leg colour is dark in P.collybita but paler in P.ibericus, though not as pale as the legs of willow warbler. A bit hard to be sure about the leg colour in this photo, probably quite dark though. There is clearly yellow on the flanks as there should be in P.ibericus.

This is the Telford bird, apparently a classic P.ibericus. Bear in mind that it was a much sunnier day, but you can see  that it has a distinct supercillium, yellow in front of the eye and a strong eyestripe. Not much sign of yellow in the flanks though, which is a feature of P.ibericus, in fact the Lancashire bird appears to have more yellow in the flanks than this bird. Ear coverts are somewhat paler here than on the Lancashire bird, emphasising the supercillium and eyestripe. Not much in it though.

So which bird is this? It's the Lancashire bird, but notice how pale looking, almost white the underparts are, and notice the pale lemon yellow undertail coverts and supercillium, both features of P.ibericus, though perhaps not as distinct here as they should be. However, the eyestripe is also not very distinct, consistent with this bird being P.collybita.

The Telford bird, very pale underparts, lemon undertail coverts. Where have we seen that before? A much more distinct supercillium and eyestripe than the Lancashire bird though. Also look at the leg colour, not obviously paler than the legs of the Lancashire bird, especially given how much better the light conditions were on the day.

So what's the conclusion? Well the sonogram says that the Lancashire bird is  P.collybita, the Telford bird is P.ibericus. End of story. Except that I heard the Lancashire bird call and it called like P.ibericus and NOT like P.collybita.That's as much a fact as the sonogram results.

Somebody asked me for my opinion on the Lancashire bird and I said that if it was a new bird for me I would not count it, simply because I would want my first to be a bird which was as far as possible beyond doubt, but given that I have now seen three definate Iberian chiffchaffs in the UK, the Lancashire bird will stay on my list as a possible. Personally, rather than call it an atypical common chiffchaff, I'd be happier calling it a dull, atypical Iberian chiffchaff. But I can't argue with the sonogram results. If you get chance, go and see both. Even if you believe that the Lancashire bird is P.collybita, it's surely worth a look (and listen) to help appreciate the pitfalls of identifying a potential P.ibericus. Despite not being reported now, the Lancashire bird was still present up to at least 13/04/2016.

Below are a couple of videos of the Telford bird.