Chapter 16: Drab

In the Urals, there is a narrow ‘contact zone’ where abietinus and tristis meet and their breeding ranges overlap, with some hybridisation going on. In order to sidestep this much-exaggerated problem, Arnoud visited Sergey Gashkov, a birder and sound-recordist who works at the Zoological Museum of Tomsk State University in Tomsk, Siberia, 1600 km east of the contact zone. There he recorded the full vocabulary of Siberian Chiffchaff. Magnus analysed Arnoud’s recordings when he got back, and I’ve asked Magnus to take you through the full repertoire of tristis. Here are his thoughts…

“As we described in The Sound Approach to birding, the typical call of adult Siberian Chiffchaff is very different from Common Chiffchaff, being an uninflected, pure-sounding whistle (CD2‑42). These calls may be considered to have a plaintive, sad-sounding quality, and this together with the subdued plumage tones may be why Blyth chose the name tristis (sad) when he first described Siberian Chiffchaff in 1843.

While tristis calls usually sound uninflected to our ear, sonagrams seldom show a simple horizontal line. Typically, they are shaped more like a crescent or arch: slightly rising at the start, flatter in the middle, and descending at the end. There may be subtle deviations from this, most of which are not particularly audible. In CD2-43, you can hear a medley of three call sequences recorded near Tomsk, which show how little variation there exists in adult, breeding-season calls. We are not aware of any call differences between males and females, and the limited range of variation in adult calls suggests that if any exist they must be very subtle.

As we showed in The Sound Approach to birding, juvenile Common Chiffchaffs in summer can occasionally give very tristis-like calls. We have not heard these any later than mid-August. So by the time tristis arrive in northwestern Europe in late autumn, chiffchaffs with tristis-like calls should indeed be Siberian. Arend Wassink’s photographs of Siberians trapped in Kazakhstan (van den Berg & The Sound Approach 2009) show that the variation in the plumage and bare parts colouration of Siberian is considerable. Many birders, however, continue to believe in a mythical population of ‘eastern abietinus’ with tristis-like calls. I think I know how this may have come about. 

When birders started visiting the Middle East en masse from the ‘80s, they commonly encountered birds with calls similar to tristis but an appearance much closer to abietinus. These birds were not, however, ‘eastern abietinus’. Instead, they belonged to another branch of the chiffchaff genetic tree. In western Asia there are Common Chiffchaffs with calls very similar to tristis. I am not talking about the warm brown Caucasian Chiffchaff P lorenzii, sometimes referred to as ‘Mountain Chiffchaff’, which replaces Common at high altitude in eastern Turkey and the Caucasus. Instead, I am talking about lower-altitude chiffchaffs much closer genetically and in their appearance to collybita and abietinus Common Chiffchaff than they are to either Caucasian Chiffchaff or Siberian Chiffchaff (Helbig et al 1996). These Common Chiffchaffs have been ascribed to three different subspecies: brevirostris in Anatolia, caucasicus in the Caucasus and menzbieri in northern Iran.

We have not recorded menzbieri, but we do have recordings of adult brevirostris from Turkey and caucasicus from Armenia. Brevirostris have calls that descend very slightly (CD2-44), but typical calls of caucasicus sound indistinguishable from tristis to our ears (CD2-45). Their songs on the other hand sound nothing like tristis at all, and show only slight differences from collybita and abietinus Common Chiffchaffs. None of these western Asian chiffchaffs are thought to migrate as far as tristis, so they are unlikely to reach western Europe as tristis do. It is worth remembering that Green Warbler P nitidus breeds in the same part of the world, migrates further and is much easier to recognise, but has still been recorded only once in the UK.

Now we know that Siberian Chiffchaff is not the only chiffchaff with classic ‘tristis-like calls’, let’s flip the problem over and examine whether good Siberians ever have calls that deviate from the classic type. As we saw, there seems to be no evidence of this from adults recorded near Tomsk in July. However, juveniles just out of the nest do sound quite different from adults. As in other closely related Phylloscopus warblers, the calls of very young juveniles are quieter and huskier than adult calls. They have two main call types: contact calls that inform the adults and their siblings where they are, and begging calls that the contact calls change into when an adult arrives with food. Both of these call types can be heard in CD2‑46. 

Interestingly, calls of very young tristis have variable inflections. They are typically flat or slightly descending, but sometimes rise audibly in pitch. In CD2-47, you can hear examples of descending and rising juvenile contact calls from Tomsk in mid-July.

In Western Europe, we don’t see Siberian Chiffchaffs until October, by which time their calls are no longer husky and usually sound very similar to adults. However, autumn Siberians don’t always give classic tristis calls, and often show more inflection than we would expect. Perhaps we should not be surprised if some of the plasticity in calls of very young juveniles is retained in birds only three months older. Plasticity, as we explained in The Sound Approach to birding, is the greater variation audible in young birds still learning their sounds.

Like the fledglings from Tomsk, autumn vagrants not only give flat and slightly descending calls but occasionally also variants that are inflected upwards. Here is an example of a first-winter Siberian with very good credentials (it even sang), giving rising calls in October. It was recorded by Pim Wolf in the  Netherlands (CD2-48). 

Contact calls are not the only sounds with which we can readily identify a Siberian Chiffchaff. Fortunately, migrants and wintering birds sometimes sing, and their song is highly distinctive. As mentioned already, they have been heard singing in Poole Harbour in winter. Here is an example of adult song, one of the most characteristic sounds of the Siberian forests, recorded in Tomsk in early July (CD2-49). Note that it contains many rising notes, usually lacking in Common Chiffchaff songs, giving it a much more fluent and melodious character. 

Juveniles start attempting to sing almost as soon as they leave the nest. Their attempts might not immediately be recognised as song, but compare the pitch and rhythm of the husky sounds in CD2-50 with the adult song in the background. By the time they reach Europe, these subsongs have developed into something much closer to adult song. If you are lucky enough to hear a first-winter singing, you will probably hear some plasticity, hesitation, and sometimes a whispering quality that gives away its age. In CD2-51, you can hear subsong recorded from the same Dutch first-winter with odd, upward-inflected calls that you already heard.

One neglected aspect of chiffchaff sounds is the little call-notes that are often heard between the strophes. In tristis, these notes can be described as CHUvit, having a characteristic low-high contour that distinguishes them from equivalent notes in European chiffchaffs (CD2-52). In collybita and abietinus, the notes heard between strophes are simpler, and sometimes just a single note or ‘syllable’. If there are two then the second is usually very similar to the first. In autumn subsongs of tristis, these notes are likely to be present (as indeed one was in CD2-51 at 0:01), and once in the Netherlands, I recorded some from a bird that was not singing at all (CD2-53). I suggest that birders listen for CHUvit calls as an additional means of identifying Siberian Chiffchaff. 

What about the possibility of vocal impostors, abietinus or hybrids from the narrow contact zone that have adopted calls or songs of tristis? According to a recent study, such birds are not unusual in the contact zone (Marova et al 2009). However, I suggest we should not worry too much about this, and keep things in perspective. The contact zone was revealed in the same study to be less than 65 km wide, compared to a total east-west range of more than 4,000 km. So hybrids and chiffchaffs that have learned the wrong calls must make up a very small number compared to the huge total population of tristis in the Siberian taiga. Any bird calling or singing like tristis in late autumn in western Europe is more than likely to be one. And if the bird itself is telling us it’s a tristis then that’s good enough for me.” 

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