Icterine Warbler, Hippolais icterina: Sunday, 23rd July 2022

Jonny was ringing this weekend at one of his sites. The site is not open to the public, and the landowner does not want the site named. As, according to the records, this is only the fourth record for the species in Wiltshire and it is a sensitive site, the caution is warranted.

The other records are interesting. Wiltshire’s first record was near Salisbury on the 11th June 1944. This bird was identified by song, rather than by observation or catching for ringing. Our second record was a bird caught and ringed in August 2009 near Longbridge Deverill. Most recently, one was caught and ringed by the North Wiltshire group on the Salisbury Plain Training Area on the 16th August 2020. Thanks to Rob Turner for providing this information.

So to this bird. I was sitting at home, unfortunately still housebound after my operation, when I saw I had a missed call from Jonny. I called him back and, after a bit of phone tennis, we had a chat. He was, rightly, so excited. As he put it, he was extracting birds, a number of Phylloscopus warblers, when he noticed that one was somewhat larger and, although the plumage was superficially similar, different to what he had handled before.

He had already done the hard work, taking all of the appropriate biometrics, as follows:

  1. Wing Length: 79mm (75 – 83mm)*
  2. Weight: 14.2g
  3. Tail Length: 54mm (49 – 55mm)*
  4. Tail / Wing Ratio: 68.4% (62 – 71%)*
  5. Bill Length: 16.2mm (15 – 17.5mm)*
  6. Distal Bill Length: 9.2mm
  7. Proximal Bill Length: 5.0mm
  8. Tarsus length: 21mm (19.5 – 22mm)*

* Reed and Bush Warblers: Peter Kennerley and David Pearson, illustrated by Brian Small. Helm Identification Guides, 2010

Jonny and I had a long discussion about ageing the bird and hadn’t come to any firm conclusions. He then sent me over a number of his photographs, a selection follows:

Fig. 1: Icterine Warbler

I have to say that this first photograph gave me some concerns regarding ageing the bird: is that barring a natural part of its plumage or are they fault bars. If the latter, it would strongly indicate that it is a bird of this year. However, there is also a fair amount of wear on the retrices, which would indicate adult. However, Jonny then sent over a picture of the wing:

Fig. 2: Wing showing primary & secondary feathers

This photograph is almost identical to the photograph of a post-breeding adult Icterine Warbler in Jenni & Winkler’s second edition of “Moult and Ageing of European Passerines”, Fig. 233 pp 146, with wear on P5 to P9, counting descendantly from the outside. Interesting, but we settled on it being an adult bird. If anyone with more experience of the species (this is only the second I have seen: the other was one I ringed on Skokholm in 2015) has any information regarding ageing of this bird, please contact me through the blog feedback.

Fig 3: Head Shape, typical of Icterine Warbler
Fig. 4: Underside

A great find and hopefully ringing it will generate more data on its future movements. It would be too much to hope that it might be recaptured next year.

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