TURNSTONES
turning stones to see what's underneath
TRISTIS WITH COMMON CHIFFCHAFF CALLS (2017, 2018)
- mtDNA confirmed Siberian Chiffchaffs calls like a Common
- plumage perhaps not entirely classic for tristis
- could this be a hybrigade?
Figure 1. Chiffchaff sensu lato, Meijendel, Wassenaar, Zuid-Holland, 25 November
2017. This bird showed the mtDNA of Siberian while it called like a Common.
On 25 November 2017 I trapped an interesting chiffchaff on my ringing site in Meijendel. It certainly did not look like a typical Common Chiffchaff and it had several tristis qualities to it. Basically it looked more like a Siberian than a Common (Figure 1, 2). But I had my doubts, something looked just a little bit off.
Figure 2. Chiffchaff sensu lato, Meijendel, Wassenaar, Zuid-Holland, 25 November 2017. This bird showed the mtDNA of a Siberian Chiffchaff, but it called like a Common/ Scandinavian.
Right before I wanted to release the bird, it started calling:
There you go! A typical collybita/abietinus call. A confirmation of my doubts: this was not a tristis! The spectogram confirms what the ears tells: this a rising call, not the flat (and sad) call of a Siberian.
Figure 3. Spectogram of the Chiffchaff sensu lato calls, Meijendel, Wassenaar, Zuid-Holland, 25 November 2017. Siberian Chiffchaff should show a more or less flat form, while this call obviously increases in pitch. Same bird as figure 1 and 2.
I asked Peter de Knijff to pay extra attention to this bird in his mtDNA analyses. The result was somewhat shocking: the bird showed tristis mtDNA. Yes, an mtDNA tristis with a "hueet' call.
E.g. Alan Dean already mentioned the existance of tristis like birds with Common Chiffchaff like calls on his website. More importantly there's a nearly identical record from Portland, UK in October 2014. This sound recorded bird also showed the mtDNA of a Siberian (see here; scroll a few pics down) .
Are these birds hybrigades, birds with both tristis and abietinus genes as described by Marova et al 2017 and Shipilina et al 2017?
Plumage
Other DNA sequences "proof" that most of the time I know a tristis when I see one. So why was I in doubt when I trapped this bird in the first place, even before it started calling? There were several features that both do and do not match a (typical) grey Siberian. The criteria from Dean & Svensson (2005) are helpful.
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There are no yellow tones in the plumage. None! Very Siberian like.
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... except for the underwing. The yellow seems to be just a bit too extensive for tristis (Figure 4).
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A peach coloured cheek is certainly possible in Common, but it definitely adds to the Siberian feel
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The white eyering “disappears” in the buffy eyebrow; very tristis like!
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Pure white belly reminiscent of tristis
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There are no olive ones on the head
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There are some olive tones on the mantle, but subtle. Not unlike some of the tristis we had confirmed by DNA before.
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The legs are dark brown rather than ink black (unlike tristis); some yellow on the leg feathers
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One feature stood out, the feature that caused doubt in the first place. The flanks were obviously brownish in this bird.
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As is the upper breast
Figure 4. Perhaps there's a bit too much yellow on the underwing of this Chiffchaff sensu lato for a regular tristis, Meijendel, Wassenaar, Zuid-Holland, 25 November 2017.
Figure 5. The flanks of this Chiffchaff sensu lato are somewhat brownish, while the grey tristis type we normally get have more whitish flanks. The leg feathers show some yellow and the legs themselves are dark brown rather than the ink black of most tristis, Meijendel, Wassenaar, Zuid-Holland, 25 November 2017.
Now what?
In 2018 Peter de Knijff and his students will run a second test on all tristis we've trapped at five sites over the past five years. In this second test we'll try to figure out if any introgression with abietinus can be found. This will hopefully give new insights in stray Siberian Chiffchaffs in NW Europe - and in this bird in particular!
Acknowledgements
Peter de Knijff is thanked for the DNA analyses. Alan Dean kindly shared his thoughts on this bird and Thijs Fijen put me on the trail of the Portland bird earlier.
References
Dean, A. R. & L. Svensson. 2005. 'Siberian Chiffchaff' revisited. Br Birds 98: 396-410
De Knijff,, P., V. van der Spek & J. Fischer. 2012. Genetic identity of grey chiffchaffs trapped in the Netherlands in autumn of 2009-11. Dutch Birding 34:6, 386-392
Marova, I., D. Shipilina, V. Federov, V. Alekseev & V. Ivanitskii, 2017. Interaction between Common and Siberian Chiffchaff in contact zone. Ornis Fennica 94: 66-81
Shipilina, D., M. Servyn, V. Ivanitskii, I. Marova & N. Backström, 2017. Patterns of genetic, phenotypic, and acoustic variation across a chiffchaff (Phylloscopus collybita abietinus/tristis) hybrid zone. Ecology and Evolution2017:7, 2169–2180