TURNSTONES
turning stones to see what's underneath
THE UNEXPECTED TRISTIS LOOK-ALIKE (2017, 2018)
by Vincent van der Spek & Peter de Knijff
- Short note about Common Chiffchaffs that approach Siberian in appearance
- ID of doppelgängers confirmed by mtDNA or sound recordings
- Subtle features to ID some of these look-alikes
Figure 1. Siberian Chiffchaff look-alike, but nominate Common based on mtDNA. Same bird as figure 7. It surely does look a bit off for tristis, yet I can't say why! Meijendel, Wassenaar, 12 November 2014.
Over the past ten years we did more work on chiffchaffs than what can possibly be healthy. But there's still so much to learn! Scandinavian (Svensson 1992) and the possibility of Scandinavian x Siberian hybrids (Marova et al 2017) are often mentioned as pitfalls for Siberian Chiffchaff identification. We however found look-alikes in nominate Common Chiffchaffs, too.
We've learnt a great deal about the identification of Siberian Chiffchaff (Phylloscopus (collybita) tristis) in a NW European context since our first series of mtDNA-analyses (De Knijff et al 2012). Back then the big question was: what are these grey chiffchaffs we're trapping? Based on mtDNA they all turned out to be tristis; none of them where Scandinavian Chiffchaffs (Ph. c. abietinus).
In a second survey (fieldwork: 2012-2017) we try to find out a) if Scandinavian occurs in the Netherlands and if so, b) when; c) what they look like, and d) if there are Scandinavian genes in the Siberians we trap (hence; do we get any hybrigades over here? For more information on those see Marova et al 2017 and Shipilina et al 2017).
This will lead to several publications. With the work still running we won't reveal too much for now. But we do like to share some thoughts about tristis look-alikes.
The good news is that, based on the analyses by Peter and his students, all birds with tristis mtDNA from my (=Vincent's) ringing site (Meijendel, Wassenaar, the Netherlands) were indeed ringed as Siberian Chiffchaff. We didn't miss any!
However, to our surprise two birds trapped in Meijendel and identified as Siberian turned out to be Common Chiffchaffs (Phylloscopus c. collybita) based on mtDNA (so 'not even' Scandinavian). As it turned out, the ringers in Castricum had a similar case. A quick scan amongst keen ringers revealed that all of us would have identified these three birds as tristis, or at least as tristis candidates. Remarkably the two birds from Meijendel are from the same date. A second check gave the same results.
Birds like that can easily be misidentified in the field. In these birds I found several features that both do and do not match a (typical) grey Siberian. The criteria from Dean & Svensson (2005) are helpful here.
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There are no yellow tones in the plumage. None! Very unlike Common. The yellow on the underwing of one bird would even be very little for a tristis (Figure 2)!
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A peach coloured cheek is certainly possible in Common, but it definitely adds to the Siberian feel. The colour does seem te be a trifle less warm, though.
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The white eyering “disappears” in the buffy eyebrow; very tristis like!
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Pure white belly and flanks reminiscent of tristis (Figure 3).
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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 were not ink black, more dark brown, so unlike tristis
Figure 2. To me this bird ticks most Siberian Chiffchaff boxes, yet its mtDNA tells another story: nominate Common Chiffchaff, Meijendel, Wassenaar, the Netherlands, 12 November 2014. Remarkably, this was on the same day as another proven misidentified bird. The bird does look a bit off for tristis, yet I can't say why!
Figure 3. Note the whitish flanks of this Siberian Chiffchaff, Meijendel, Wassenaar, The Netherlands, 30 October 2014. ID confirmed by DNA-analyses.
The puzzle
These are puzzling birds... The features shown are (nearly) all good for Siberian, but their mtDNA tells a different story: nominate collybita... Isn't that fun? And isn't it intriguing that all these tristis doppelgängers date from November. I've never seen anything like it in summer! We really wonder if this is within the upper limit of the normal variation, or if these birds could for instance be of a collybita population we do not fully understood. Still so much to learn!
But don't despair after reading this! Note that by far most birds that look like tristis, show the mtDNA of tristis!
Acknowledgements
Peter de Knijff is thanked for the DNA analyses. Jan Visser, Arnold Wijker and Maarten Verrips provided additional information on birds in Castricum or Meijendel.
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
Svensson, L. 1992. Identification Guide to European Passerines. Stockholm.