Wednesday, 3 July 2019

Greenish Warbler Update

After the reaction of some very experienced birders and ringers on Twitter regarding photographs posted by myself and Steve Rogers I decided to try and do some more research on the Greenish Warbler at Porth Joke. I had heard that Steve Rowe had some recording of the bird singing and he very kindly supplied me with the original recording. The next step was to contact a very helpful Martin Cade who gave me contact details for Magnus Robb from Sound Approach team and his colleague Roy Slaterus who has recently been working on the first Green Warbler for Holland. (interesting article on this bird here:

Both Magnus and Roy quickly replied to me and I was delighted that they would help analyse the recording and get back to me with their results. In super quick time I soon had two excellent and informative replies from these sound experts with detailed notes and a sonogram which seems to suggest that the bird was in fact a Greenish Warbler. Snippets from their email include:

Roy Slaterus :

Yes, I agree. This sounds like Greenish Warbler song to me. These are things I look at, when separating Greenish from Green.

-          A short high-pitched ‘jeet’ at the very start of (almost) every song phrase is typical for Greenish. This intro note is lacking in Green. But I can see it in the Porth Joke recording.

-          The song of Greenish is usually broken up into sections, like Magnus explained. Vaguely reminiscent of Wren or even Chaffinch (in Dutch: ‘vinkenslag’). In Green this is less obvious. But I can see it in the Porth Joke recording.

-          Greenish Warbler song consists mainly of rather simple elements and descending notes are dominating, whereas Green Warbler song is a bit more rich with more V-shaped notes. The Porth Joke recording is similar to Greenish in this respect (if my judgement is correct; the recording sounds a bit affected in some way).

Many Greenish Warblers sing longer song phrases than those recorded at Porth Joke. But it is within variation, I would say.

Magnus Robb:

I think this is really a bona fide Greenish Warbler. Lets see if Roy agrees. It sounds like several examples I have recorded and it doesn’t those of Green that I have just been listening to. The structure has a very slight hint of Wren about it, in the way it is broken up into sections whereas Green has less contrast in frequency range etc within the strophe. Also, as Roy recently pointed out to me, the little intro note just after 13 seconds is typical for Greenish whereas Green doesn’t have it.

In the mean time Steve Rowe remembered a post from Portland Observatory of a Greenish Warbler trapped in June. It was very interesting to see that the bird in the hand showed plumage characteristics pro Greenish (such as a grey cast to the mantle and white looking underparts). Yet the image of the bird in the tree's depicts a bird that looks much brighter and yellower especially around the face so I can only imagine that perhaps the Porth Joke bird was affected by the light and the green foliage in our photographs as in the field it looked much whiter underneath and showed a contrast similar to Wood Warbler between head colour and flank, underpart coloration.  A link to this post is here:

Comments I have heard about the structure of the Porth Joke Greenish being too weak billed may have some relevance but I wouldn't put too much onus on this feature. My ringing experiences have taught me that there is much overlap with biometrics in Phylosc Warblers. Another interesting comment from Kester Wilson was that Greenish Warbler seems to show much more solid dark lores (which the Porth Joke bird shows) in comparison to the relatively plainer faced Green Warbler from images on the internet.

So in the end it does seem that the bird was a standard Greenish Warbler Phylloscopus trochiloides. A great record for Cornwall this spring and a really good find for Steve Rowe. I certainly feel more prepared should a Green Warbler turn up again in Cornwall and I have learnt that the Greenish complex is more difficult than I realised. Good photographs from a series of angles in good light are vitally important to determine positive ID yet field observations and notes are just as important as they have always been in order to compliment the pictures and prove that they are accurate as all cameras can show different hues and colours on a bird. Sound recordings of calls and songs are going to become more and more important in separating difficult passerines and when possible I am definitely going to make more of an effort to get sound recordings. Birds trapped and ringed at migration sites and observatories will also add to our understanding through DNA analysis and in the hand descriptions. With a Green Warbler turning up on the Lizard this year and with an autumn bird on Lundy last year us birders should always keep an open mind with what can and will turn up in Cornwall.

A Special Thanks to Steve Rowe, Magnus Robb, Roy Slaterus and Kester Wilson for their help, knowledge and ideas.

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