Tune into Reed Bunting
The month of March offers birders of any ability the chance to get out there and learn what the Reed Bunting means by its song
Dominic Couzens reveals what the Reed Bunting means by its song. Will you hear it soon?
The reviews aren’t kind. “A brief, simple verse,” says the Collins Bird Guide, without much enthusiasm. The RSPB Handbook of British Birds calls it “Repetitive… a collection of a few metallic notes ending in an unremarkable flourish.” Meanwhile, Britain’s Birds is downright rude: “Monotonously repeated… disjointed, short, simple, slow…” it declares, damningly. Oh dear! You wouldn’t wish your own vocal efforts to be described so harshly, would you? You might just decide to keep quiet. Thankfully for us, though, the Reed Bunting doesn’t keep quiet. And that’s just as well, because this particular songster tells a remarkable tale within its “short and repetitive” ditty. And you might be surprised to know that you can decode quite a bit for yourself, if you listen carefully. So, pick a still March day, get over to your nearest reedbed,
find yourself a handsome male songster and prepare to be immersed in a world you thought would have been kept secret. Just in case you don’t know the song, it is one of the easiest to identify in early spring. It is indeed a collection of three to five notes delivered in halting fashion. It has been memorably described as “like a child managing to count to three and then forgetting what’s next.” It could be transcribed as “Three… blind… mice,” or if you do prefer a more abstract version, try: “scrip… scrip… scria… srisrisirr” (Collins Bird Guide again.) The real live bird’s song is easier to grasp than the transcriptions on the page, and so long as you can hear it, a Reed Bunting is readily identifiable. Besides, in March, not a lot else is singing from the reed tops. I have elaborated on the identification of the song for a reason. Anybody who has really listened to Reed Buntings will have noticed that their efforts are not all the same. There are, in fact, two song types, and the distinction between them is very clear. Sometimes, the song fits the descriptions above – slow and hesitant, with three-four syllables. Sometimes, on the other hand, the song is faster, with more syllables (five-six) more rapidly delivered in the same length of song phrase. The ‘Slow Song’ contains fewer notes at moderate pace, while the ‘Fast Song’ has more notes delivered at a quicker pace. However, the interval between song-phrases, the gap they leave between the songs, is longer in the ‘Fast Song’.
Slow song... fast song
Although this sounds an obscure distinction, I promise that anybody can hear the difference. It might also seem arcane, but it is dynamite, because it also lets you into a truly intimate secret. It is no less that paired males sing the ‘Slow Song’ and unpaired males sing the ‘Fast Song’ (females don’t sing.) In other words, you or I can tell a bird’s marital status just by listening to it. There is no other bird song through which it is so easy for us to eavesdrop on an individual’s fortunes. ‘Slow Song’ is sung towards the mate, reassuring her that a male is stationed on territory and everything is fine. It has been shown that female Reed Buntings incubating eggs tended to take more breaks to feed when a male was singing, which suggests that long bouts of male song served as signals that the coast is clear, and it is safe to leave the nest for a while. On the other hand, the ‘Fast Song’ is sung for the purpose of attracting a mate and is therefore delivered toward nobody in particular. You might say that it is offered hopefully, rather than helpfully. This song reveals that a male is available, while the ‘Slow Song’, technically at least, reveals that a male is taken – or at least, that it has a social mate and is involved in a breeding attempt. Males that lose their mates during the season switch their song type from Slow to Fast. Well, that’s fun, isn’t it? Next time we visit a reedbed we can empathise with the singing bird. But that’s far from the end of the story. In 2009, a Swiss study discovered something completely unexpected: paired male Reed Buntings sing a different song at dawn, compared with the rest of the day. It is very unusual indeed for any new songs of common European birds to be described, so this was sensational stuff. They found that male Reed Buntings with mates sang a great deal faster than usual during the dawn chorus, an almost continuous stream of short song-phrases lasting 2.5 seconds each, with a very short, half a second gap between. This is so different from their leisurely day-song, and also to the ‘Fast Song’ (in which there are much longer gaps between phrases) that we can all be confident that the Reed Bunting actually has three song types. But why would a paired-up male change its tune at dawn? The answer to this question takes us much deeper into the world of the Reed Bunting and its breeding behaviour. The short answer to the question of dawn song-change is that a paired male is advertising itself for copulations outside its own pair-bond. Dawn is generally a time when a female, having perhaps just laid an egg, is at its
Just in case you don’t know the song, it is one of the easiest to identify in early spring
most fertile, requiring the next egg on its production line to be fertilised. The dawn message is an invitation from a neighbouring male to be the one to carry out the job. Regular readers of this column will have heard before that copulations outside the pair bond (EPCS) are routine among many common British birds, from Blue Tits to Swallows.
Strange behaviour
Such birds have an arrangement in which a pair will make a ‘social’ pair bond, and carry out roles (incubation, chick feeding) within it, but both will indulge in copulation outside it. As a result, a consistent percentage of eggs across broods will not be fertilised by the male parent. This is normal. What is not normal, however, is the extraordinary extent to which this particular species, the Reed Bunting, indulges in EPCS. A study at Rutland Water (Rutland Water! The paper should be entitled ‘Bird Af-fairs’) found that no fewer than 55% of young across all nests in the study area were not fertilised by their social ‘father’. This is one of the highest rates recorded for any bird in the world, and the highest in any British bird in which social monogamy is the typical arrangement. A total of 97% of all individual females copulated outside the pair bond, and seeking sex in neighbouring territories accounted for 40% of the average male’s entire reproductive output. There are, however, a few patterns within this apparently wild and indiscriminate mating system. Older and, by definition, more experienced males sired significantly more extra-pair offspring than did younger birds and, at the same time, older and more experienced females ensured that more extra-pair offspring were raised in their own broods. This suggests that older males were better at circumventing any protective measures, such as alert mate-guarding, that might be attempted by their younger neighbours. It also suggests that females must learn how to dodge a mate’s preventative strategies more effectively over the years! So, now we know that Reed Buntings advertise their intentions at dawn during the breeding season. We can hear it. And we can also guess that, during these exchanges, the oldies are cheating the youngsters. The truth is, too, that a singing Reed Bunting has the ideal riposte to all the critics of its supposedly unimpressive song, one that is often quoted by frustrated musicians. It isn’t all about the music, it’s about the meaning.
Reference: Suter, Ermacora, Rieille and Meyer, 2009. A distinct reed bunting song and its relation to extrapair paternity. Animal Behaviour Vol 77, 2 (473-480).