Odd Chiffchaff

On 9th April 2007, I encountered a Chiffchaff with a song which sounded similar in some respects to that of an Iberian Chiffchaff. Having researched it and discussed it with a number of birders experienced with the species (to whom, thanks!), I became pretty sure it was just an odd Chiffchaff, not an Iberian Chiffchaff. However, some notes and photos appear below so please make your own mind up (and let me know what you think).

It was on private land near Swanton Morley in Norfolk and remained until at least 9th May. By this time, like the other Chiffchaffs, it was singing less than when it first arrived. There were several normally-singing Chiffchaffs in the same area, including 2-3 in the same trees on the first day.

By complete coincidence, an apparently real Iberian Chiffchaff (the first for Norfolk) turned up not many miles away at Colney, Norwich on 22nd April. With the benefit of now having seen and listened to that individual I have updated the text that follows.

Chiffchaff, Wensum Valley, 9-Apr-07
Chiffchaff, Wensum Valley, 9-Apr-07

Chiffchaff with unusual song, Swanton Morley (Norfolk, UK), 9th April 2007

 

More photos will follow later, but first some notes:

 

Song

Iberian Chiffchaff Phylloscopus ibericus (or Ph. bremhii depending on your taxonomic reference) has recently been split from (Common) Chiffchaff Ph. collybita. Identification can be extremely difficult but the song is distinctive. Before I describe my bird I'll just outline what Iberian Chiffchaff should sound like, so far as I understand it.

I have listened to a number of recordings of Iberian Chiffchaff, on the internet, BWPi and the Bird Images "The Birds of Britain and Europe" DVD. Most of the internet recordings were of extralimital birds - recordings from Iberia seem to be in short supply! My understanding of what Iberian Chiffchaff's song should sound like is based on these recordings, discussions with experienced birders, a very hazy memory of one in Portugal and much fresher memory of the Colney bird on 22nd April.

So far as I now understand it, Iberian Chiffchaff's song can have up to four sections (which all run into each other):

  1. The first few notes are similar to Chiffchaff. It seems that this section is typically 4 notes long, though not necessarily so. If the recordings I've listened to are typical then although these notes are Chiffchaff-like, they do not vary significantly in pitch as Chiffchaff typically does, i.e. "chiff-chiff-chiff-chiff" rather than "chiff-chaff-chiff-chaff". There is slight pitch variation however on the recordings I've listened to and of course the amount of pitch variation on Chiffchaff is variable (I've listened to a couple recently which consistently had only very slight pitch variation for the first 7-8 notes before "chiff-chaffing" normally). The Colney bird's song contains this section and it matches extremely well to recordings of Iberian Chiffchaff.
  2. The second section consists of notes which are sometimes said to resemble Chiffchaff's call-notes. I don't think that's a good description though as they're less subtle and more similar in tone to the first section of the song. BWPi describes them as "emphasised 'swüid' units" which is better. The Colney bird's song contains this section. It seems that there are typically just 1-2 of these notes.
  3. Then there is a distinctive rattling sequence. The notes are much faster than the rest of the song and on similar pitch, perhaps slightly descendent. They are nothing like anything that's typically heard from a Chiffchaff and are more similar to part of a Chaffinch song, or even Lesser Whitethroat. It seems to consist of 4-5 notes typically. The Colney bird's song contained this section consistently, often 5 notes, sometimes longer.
  4. Finally there may be some more Chiffchaff-like notes, although whether there are ever more than 2-3 notes, and whether they can ever be as rambling in pitch as on a Chiffchaff I am not sure. This section is often absent and isn't mentioned in BWPi. It was absent on the Colney bird (at least while I was there).

I don't think it's essential for an Iberian Chiffchaff to show all of these parts every time it sings, but the first three probably need to be uttered regularly for an extralimital bird to be convincing.

Here are some links to recordings of the Colney Iberian Chiffchaff, I think recorded by the finder:

The bird I discovered at Swanton Morley did not have the typical song of a Chiffchaff and consistently included the rattle section that is typical of Iberian Chiffchaff. It was not however typical of Iberian Chiffchaff in every respect. The following is my attempt to describe the song on the day I found it:

I first watched it for a prolonged period during the morning (roughly 8.00 am to 9.00 am) and during this time it gave a fairly consistent song. The full song was in three sections, although all three sections ran into each other. The first section was a few Chiffchaff-like notes (varying number, usually at least 4, up to 7-8). The second section was usually 4, sometimes 3 and occasionally up to 8 loud notes, more rapid than the first section. The nearest thing I can compare this to is the start of a Chaffinch song, but here the notes were almost on the same pitch (very slightly descendent). On the few occasions that this section lasted more than 4 notes there was a very slight pause after the 4th and then there were 3-4 more, so it was as if it was repeating this section. Finally the third section consisted of usually two more Chiffchaff-like notes.

When I first watched it, it often gave only the first and second sections, omitting the last, and sometimes just gave the first section. As it warmed up it gave the full three-section song increasingly consistently.

I returned at lunch time when it was cloudier and cooler. It was still singing in a similar fashion. However on a few occasions (usually several times consecutively), it completely omitted the interesting second section and hence sounded just like an ordinary Chiffchaff. Also on a few occasions when it gave the full three-section song, the final section lasted significantly longer than the two notes that were typical during the morning.

On occasion, when I had lost the bird for a few minutes, and then it began to sing, I was able to tell that it was this bird even before it began its distinctive second section - the first bit sounded more urgent than the surrounding Chiffchaffs.

I returned again late afternoon and it was generally less vocal. However when it did sing it was usually the same as before. Sometimes it completely omitted the first section and began with the rattle - occasionally all it did was this rattle.

On the day I was struck by the significant similarity between this bird's song and the recordings I could find of Iberian Chiffchaff. In particular the rattle section was very distinctive and unlike anything I've ever heard from a Chiffchaff (nothing like the quiet scratchy section that you sometimes hear during a Chiffchaff song). However at no point did I hear the second section of classic Iberian Chiffchaffs' song, the "emphasised 'swüid' units". Also the first and final sections were more varied in pitch and thus more Chiffchaff-like than I now understand is typical of Iberian Chiffchaff.

Tom McKinney's website has a link to a recording of the accepted record from Northumberland in April 2004. This appears to include the second section, but only a single note.

 

Appearance

In the morning when it was sunny, this bird's appearance was completely different to how it appeared later on when it had clouded over.

In the morning, it appeared a much brighter bird, rather bright green above and with distinctly yellow fore-supercilia (yellow in front of and above the eye), bright yellow streaking across the upper breast and yellow on the vent. In the afternoon, it appeared remarkably different, looking dull olivey above and more buff than yellow elsewhere. The only strongly yellow parts that were apparent in the afternoon was around the alula.

I think the legs and feet were slightly paler than typical Chiffchaff, but to be honest I look hard at too few Chiffchaffs to be sure and I've certainly seen Chiffchaffs with much paler legs. The bill seemed more a bit more extensively pale than is typical of Chiffchaff, though at least one other Chiffchaff I looked at today was similar. Paler legs and feet, and paler bill are both apparently features of Iberian Chiffchaff, but as with all the appearance-related features, far from diagnostic.

As I understand it, the average Iberian Chiffchaff is supposed to have more, brighter yellow than the average Chiffchaff. This bird did show some evidence of bright yellow, though this all but disappeared when it got cloudy. I'm not sure if Iberian Chiffchaff would typically show more yellow on the throat and undertail-coverts than this bird showed.

Iberian Chiffchaff is said to have brighter greener upperparts, especially on the rump. This bird appeared quite bright and green in the sunshine (the green not shown particularly well on any of the photos), especially on the rump, but in cloud it appeared a dull brownish-olive.

The ear-coverts were buffish, lacking yellow, even in the sunshine. The fringes to the wing feathers were not particularly bright either. The white eye-ring was distinct below the eye - on Iberian Chiffchaff it is supposed to be less distinct than on Chifffchaff.

Here are the photos... They're cropped and some have minor adjustments - if you want to see the original image, click on the photo - the larger photo that will come up is unaltered except for resizing to fit it on the page.

Chiffchaff, Wensum Valley, 9-Apr-07 Chiffchaff, Wensum Valley, 9-Apr-07

The rump appeared slightly paler and brighter than the rest of the upperparts. Note the leg dangling on the left hand photo - I think it was injured as it seemed to be dangling for most of the time. It's rather dark reddish brown, a bit paler on the feet.

 

Chiffchaff, Wensum Valley, 9-Apr-07 Chiffchaff, Wensum Valley, 9-Apr-07

The right hand photos is one of the better ones for showing how pale the base of the bill appeared. The lower mandible was pale at the base and the pale extended towards the tip along the cutting edge.

 

Chiffchaff, Wensum Valley, 9-Apr-07 Chiffchaff, Wensum Valley, 9-Apr-07

The eye-stripe and loral line looked particularly dark at certain angles, and I think that helped to make the pale supercilium stand out.

 

Chiffchaff, Wensum Valley, 9-Apr-07 Chiffchaff, Wensum Valley, 9-Apr-07

Can anyone do anything with the wing-formula from the left hand photo here?! The right hand photo is the same as the large one at the top of this page. Note the yellow streaking across the breast. There's also some yellow on the throat, especially at the sides.

 

Chiffchaff, Wensum Valley, 9-Apr-07 Chiffchaff, Wensum Valley, 9-Apr-07

The right hand photo is the same as the large one at the top of this page. On these note the yellow on and around the vent and otherwise rather clean whitish belly.

 

Chiffchaff, Wensum Valley, 9-Apr-07 Chiffchaff, Wensum Valley, 9-Apr-07

This shows the yellow front half of the supercilium.

 

The following photos show how much duller this bird appeared when it became cloudy. The yellow in the supercilium, on the throat and breast, and on the vent almost completely disappeared. The upperparts lost their greenish tinge and overall the bird appeared dull buffy-brown - completely different to how it had appeared in the sunshine!

Chiffchaff, Wensum Valley, 9-Apr-07 Chiffchaff, Wensum Valley, 9-Apr-07
Chiffchaff, Wensum Valley, 9-Apr-07 Chiffchaff, Wensum Valley, 9-Apr-07

This appearance of the Colney bird is actually very similar to this bird. The general tone of the upper and underparts was very similar to how the Swanton Morley bird appeared in the duller light (the weather at Colney was bright, but it was hazy without direct sunshine). There was no sign of yellow on the head while I watched it, and the sides of the breast were brightest yellow. There was also some yellow coloration on the vent in the same location as on the Swanton Morley bird.

I was able to detect the slightly longer-winged appearance of the Colney bird - something I could not make out on the Swanton Morley individual.

Here's a couple of poor record shots of the Colney Iberian Chiffchaff:

Iberian Chiffchaff, Colney, 22-Apr-07 Iberian Chiffchaff, Colney, 22-Apr-07

 

Conclusion

Could it be an Iberian Chiffchaff? Perhaps. But given that Iberian Chiffchaff is extremely rare in the UK (never previously recorded in Norfolk), and given that it wasn't typical of that species in either song or appearance, it probably wasn't.

So what was it? There are basically three other options - 1) a hybrid between a Chiffchaff and an Iberian Chiffchaff; 2) a Chiffchaff that has "learnt" phrases of Iberian Chiffchaff, presumably on its shared wintering grounds; or 3) nothing more than just an odd Chiffchaff. I suspect 1) is unlikely, though possible I suppose. So it's between 2) and 3) for me, either way a Chiffchaff.

Although I don't think my Swanton Morley bird is an Iberian Chiffchaff, it was an interesting and unusual bird and for me extremely educational.

A number of other claims of Iberian Chiffchaff in the UK have been confusing. Some have been more promising than this bird and could well have been Iberian Chiffchaffs but have never been adequately resolved and there remains a possibility that some were simply odd Chiffchaffs, perhaps ones that have been mixing with Iberian Chiffchaffs during the winter.

Here are recordings of two birds that have been mooted as possible Iberian Chiffchaffs:

I didn't see or hear either of these, but listening to the recordings it seems to me that the Dibbinsdale bird is pretty similar to Iberian Chiffchaff but lacking the second section. I would imagine that there is still a very real possibility that this bird was indeed an Iberian Chiffchaff. The recording of the Skelmersdale bird sounds peculiar, but not much like an Iberian Chiffchaff to me. In fact I think the Swanton Morley bird is closer to what an Iberian Chiffchaff should sound like than this recording of the Skelmersdale bird.

These odd Chiffchaffs are not to be confused with the mixed singers which include phrases typical of both Chiffchaffs and Willow Warblers that are also sometimes reported. I saw one such bird at Cockthorpe in Norfolk in May 2004 and this was quite different. These birds are often also intermediate in appearance between Chiffchaff and Willow Warbler and I imagine that at least some of them are hybrids between those two species. A Note published in the May 2007 edition of British Birds magazine offers the alternative view that as most have the plumage characters of Willow Warbler, most, or all, such birds are in fact mixed-singing Willow Warblers and not hybrids.