Part 7: Magnus Robb and ‘The Blackcaps’

Mimicry, hybridisation, mixed singers and dialect

Magnus is a composer by vocation, and his compositions have titles a birder can be proud of, like Ancient language of the birds, and Sprosser. For one of his compositions, Summoning Dawn; the rubythroat dreaming, he recorded a Siberian Rubythroat Calliope calliope, slowed down its phrases and scored them for voice. The BBC who commissioned the piece then arranged a performance on the radio. 

Songbirds are also inspired this way and mimicry provides most of a bird’s raw material for its own fine compositions. Young songbirds experiment and copy their parents and on returning to their breeding areas then copy the song phrases of the other birds nearby, often the children of their father’s old neighbours. The adults on the other hand behave more like avian DJ’s than composers. They take traditional sound samples of other species, and mix and match them with whatever is fashionable in their neighbourhood at the time. Immigrants bring in new song phrases that catch on. They do it all to impress the girls or the neighbours. 

Sounds like your local music scene? We can take the analogy further. Listen to this band; we’ll call them ‘The Blackcaps’. One of their fathers took a Great Tit phrase, sampled it, and incorporated it into the local song repertoire. Like a number-one 

record, it’s become very popular, and now they’re all singing it (CD2-34). I don’t know how long they’ve been singing along this way but research suggests that new song types develop in chaffinches in less than 300 years (Sick l939, Armstrong l963) while Indigo Buntings Passerina cyanea can “diverge from a common ancestral song theme in less than ten years” (Baptista in litt). 

The success of a particular song phrase in a neighbourhood’s shared repertoire depends on who is singing it. If a first-year male arrives late in the season singing a new phrase, it is not likely to catch on: he is not likely to be very popular with the females. Females are impressed with males already established in the neighbourhood with a rich repertoire and reward them with extra-pair copulation. A new song by an established and successful male, sung early in the breeding season, has a far greater chance of being copied. The first-year birds in a group of songbirds start with a lot of experimentation and then revert to the songs being sung by the surrounding adults. One adult singing the new ‘number one’ doesn’t guarantee its success either as it needs to be sung by several males to become successful. This way, song repertoires slowly evolve through improvisation and the introduction of new songs by immigrants.

In the context of identifying birds by sound, mimicry should not be seen as a big problem. Most mimics quickly betray their real identity through the use of other diagnostic sounds in their song, which are unique to their own species, or through the framework the imitations are made to fit into. Listen to the structure of this Common Starling song (CD2-35). Starlings are well known for being mimics, but what is less well known is that they incorporate these imitations at a set point in each song. They start with a series of whistles from their collection, they then go into a bit of garbled song including up to 20 imitations of other bird sounds but also noises like telephones etc. They then finish with a series of rattle phrases followed with a flourish of high pitched notes. Catchpole & Slater (1993) explain all this and go on to point out that starlings seldom finish a song as they are easily distracted in which case they just start it again.

Common Starlings don’t just go for any imitations though. A research group that tried to tutor starlings by playing them songs on tape recorders failed, as the starlings ignored the songs that they were supposed to learn. After a while the researchers noticed that while ignoring the bird songs, the starlings had “mimicked the sounds of the tape recorder reels turning, the tape hiss, and the coughing of the human ‘in charge’” (West et al 1983).

Common Redstart Phoenicurus phoenicurus incorporates imitations into its song, although you have to be really fast to hear them and they are normally at the end of the song phrase. Even relatively simple songs may be adorned with a sound or two pinched from another species and, in many parts of Europe, Common Chaffinches sometimes use what sounds exactly like a Great Spotted Woodpecker’s kit call in their songs, normally at the end. It is surprising how easy it is to get caught out by this when you are searching for rare woodpeckers in eastern Europe. Listen to calls of Great Spotted (CD2-36a). Then see if you can hear the same call at the end of a chaffinch song (CD2-36b). 

One of the main ways songbirds acquire their repertoires is through song matching. By copying each other and repeating what they just heard, they reinforce the popularity of certain song phrases. The recording of song-duelling Thrush Nightingales in CD2-37 was made on the 9th of May, shortly after the birds returned to their breeding grounds in north-eastern Poland. Both were probably still unpaired, so they were singing in the hope of attracting a mate, and to mark out their territories. In the recording, you can clearly hear that the two birds share much of their repertoire. The slightly closer bird on the left sings phrases that are answered by very similar ones given by the slightly more distant bird on the right. From 0:54, the roles are reversed and the bird on the right takes the initiative. 

Marsh Warbler is the best rapper in natural history and its song is astonishing in its speed and richness. An individual bird will use around 70 samples (imitations), with over 200 species known to be in the repertoire. This was researched in a series of papers by Françoise Dowsett-Lemaire (eg, 1979), who used sonagram technology to illustrate this diversity. She discovered that Marsh Warblers learn their song from other birds that they meet on their travels, both European and African species. CD2-38 is a recording of a Marsh Warbler on territory in the Netherlands. Finnish birders say that if you are unable to keep up with the impersonations in a song, it’s a Marsh Warbler (and not a Blyth’s Reed Warbler). Not only are there lots of different imitations, but Marsh Warbler makes it more difficult to keep track of them by constantly speeding up or slowing down. We have made it easier for you to hear a few of them; in CD2-39, you can hear several imitations of familiar European species cut from the first 20 seconds of the recording, each followed by the real thing. Later in the Marsh Warbler song, see if you can also hear the following European species: House Martin Delichon urbicum, Willow Warbler, Common Linnet and European Greenfinch. More exotic species the Marsh Warbler heard along its migration route include Purple Sunbird Nectarinia asiatica of eastern Arabia and southern Asia (imitated at 0:20) and Blue cheeked Bee-eater Merops persicus of the Middle East and much of Africa (imitated briefly at 2:02). Françoise Dowsett-Lemaire would also have recognised many African species in the recording, but that’s not our forte.

While Marsh Warblers are well known for imitating, Blyth’s Reed Warbler and European Reed Warbler also like to have a go. These two, however, sing at a much more steady pace. European Reed’s song is medium paced with a very regular, even boring, delivery. Listening for the song tempo can be particularly important in recognizing a European Reed that indulges in more obvious mimicry than usual. Have a listen to this song of a mature bird on its territory (CD2-40), with only a few noticeable imitations (these include Marsh Harrier Circus aeruginosus, Eurasian Coot and Common Tern).

Next, listen to the typically slow and repetitive song of a mature Blyth’s Reed Warbler established on its territory (CD2- 41). Imitations heard during the first 30 seconds include yellow wagtail Motacilla, Common Rosefinch, Yellowhammer E citrinella, Mealy Redpoll and Tree Sparrow P montanus. If you are able to keep up with the imitations, it’s more likely to be a Blyth’s Reed than a Marsh Warbler.