Mark's Articles
9 - In your dreams (continued)
Melodious Warbler Hippolais polyglotta Texel, Noord-Holland, Netherlands, 6 October 2008 (René Pop).
Melodious Warbler
There are two main ways to identify the song of Melodious Warbler, or any other species for that matter. One of those is immediate and instinctive. You listen to the general moment-to-moment texture of the song, alert for any peculiar sounds or features that attract your attention. This is like a 'jizz' approach to sound identification. The other is more analytical, requiring attention with a longer time-span, working out how the variation in the song is organised. You could compare it to analysing the structure of a bird, its primary projection, how many feathers in the tail etc. With luck, the first approach may send us in the right general direction, but the second is likely to lead to a more solid conclusion.
In the case of Melodious Warbler, one of the first things that strikes us is that this is an incredibly fast and furious song. With its moderately harsh sounds, a few squeaky notes and a scattering of whistles it sounds a bit like a Sylvia warbler that ended up in the wrong genus. If you are more familiar with Icterine Warbler song, it can sound as if Melodious has three notes for every one of Icterine. One feature that surely helps to create this impression is that Melodious embeds lots of little contact calls in the middle of its strophes, and other sounds that resemble them. Their contact call is a soft, rippling prrr, with three or sometimes four separate elements. If you are in the company of a family with fledged young, you will hear this call every time an adult is approaching the brood, and often the young respond with it too. We haven't yet recorded a juvenile Melodious Warbler subsong but have heard them giving loosely connected sequences of variations of this call and wouldn't be surprised if this develops into song. While the embedded contact calls are hardly conspicuous, much of the micro-texture of Melodious song is made up of sounds that ripple or churr in a similar way.
Melodious Warbler Hippolais polyglotta Cabriz, Sintra, Portugal, 10:03, 1 May 2020 (Magnus Robb). Song with embedded contact calls. Background: Zitting Cisticola Cisticola juncidis, Eurasian Blackcap Sylvia atricapilla and Corn Bunting Emberiza calandra. 200501.MR.100304.01
Melodious Warbler Hippolais polyglotta Cabriz, Sintra, Portugal, 09:21, 13 July 2020 (Magnus Robb). Contact calls of a juvenile. Background: Pallid Swift Apus pallidus, Short-toed Treecreeper Certhia brachydactyla and European Goldfinch Carduelis carduelis. 200713.MR.092130.02
Assuming you are hearing the right kind of texture for a Melodious Warbler, what should you listen for next? Strophes can be anything from about five seconds to well over a minute long. At the simplest level, there is a two-part structure. The first part of each strophe consists of rapid repetitions of a single sound, such as the chirp of a House Sparrow Passer domesticus or the disyllabic alarm call of a Barn Swallow, or it may be a little more complex. There may be sparrow alarm calls embedded in among the chirps, or several introductions one after the other, eg, a series of House Sparrow chirps followed by a series of Barn Swallow alarms and then a few Ring-necked Parakeet Psittacula krameri flight calls, with some degree of alternation between the three. At the simplest extreme, the entire first part may be just three repetitions of a sound totalling one second; at the other, there may be several long series of repetitions adding up to nearly a minute. At the end of the first part, there will be a single new permutation of whatever sound has been repeated last, and this is the sign that we are going into the second part.
Melodious Warbler Hippolais polyglotta Cabriz, Sintra, Portugal, 06:41, 28 May 2020 (Magnus Robb). Songs with a variety of different introductions, both in terms of their length and the sound or imitation being repeated. Background: Zitting Cisticola Cisticola juncidis, Common Linnet Linaria cannabina and Corn Bunting Emberiza calandra. 200528.MR.064144.01
What follows is the fast, furious, incredibly intense and usually longer second part of the song. At first there may seem to be endless variety. You may not recognise any mimicry, because each sound is so brief, but we believe it probably consists entirely of plagiarised fragments, micro-mimicry only recognisable as such when we tease it all apart on a computer. It is challenging to discern any order in this seemingly chaotic sequence, but worth the effort. When we stand back and listen on a slightly broader time scale, patterns emerge. The most important is that this second part of the song is largely made up of repeating cycles, or what we have been calling 'broken record' chunks. These may not be obvious at first, but then you start noticing certain striking sounds returning at regular intervals. If you look out for this pattern, you'll soon realise that hardly a single song lacks it on one scale or another. In this sonagram the first part of the song is missing, and the entire 15 second strophe consists of repetitions of just 3 seconds of material (chunks A, B and C).
Melodious Warbler Hippolais polyglotta Cabriz, Sintra, Portugal, 06:41, 28 May 2020 (Magnus Robb). Another section of the same recording from the previous sonagram, with some striking repeated cycles in the latter part of several of the songs. For example, 0:09-0:12 (two and a half cycles), 0:18-0:32 (see sonagram above), 1:04-1:06 (three cycles), 1:27-1:31 (almost two cycles). Background: Sardinian Warbler Sylvia melanocephala, Common Linnet Linaria cannabina and Corn Bunting Emberiza calandra. 200528.MR.064144.01
Repeated chunks may be anything from less than a second to over four seconds long. What often happens is that at first there are one or two short repetitions of a shorter chunk, followed by a different repetition of a much longer chunk. There may be a part of the song, typically the start of the second section, where no repeating pattern can be discerned, but sooner or later the singer will get into a rut. In extreme cases a single chunk may be repeated for 20 seconds or longer. In simpler songs the whole 'broken record' part may only involve one and a half repetitions of a chunk. Iterations may differ in one detail or another, but more often than not they contain the same elements in the same order.
Often it seems that the only way the bird can get out of the rut is to stop singing, and indeed the song usually ends quite abruptly, often in mid-chunk. Occasionally, however, it ends with a brief third section resembling the first. This is likely to involve repetitions of the same sound that will then be used as an introduction in the next song.
So, how do we tell a singing Melodious Warbler apart from an Icterine Warbler? The most obvious difference concerns the texture and the speed of change of material in the song. Icterine typically repeats each sound a few times in turn, quite conspicuously, whereas Melodious, once it gets past the first section, appears to move from one sound to the next far more rapidly. You have a sporting chance of identifying each imitated species in turn in an Icterine song, whereas with Melodious, once the second section starts you have hardly a hope in hell. And indeed, this dichotomy of first and second sections is conspicuous in Melodious but much harder to find in Icterine. Finally, if you are listening for long 'broken record' chunks, there will be more of them in Melodious song, and the average length of the chunks will be greater.
Melodious Warbler is gradually spreading northeastwards into Icterine Warbler territory, and part of the frontier currently lies in Belgium and the southern Netherlands. Melodious Warblers arrive a week or two earlier than Icterines, giving them an advantage which, along with climate change, is helping their northward advance. In this contact zone, Melodious Warblers borrow from Icterines but apparently the reverse is not true (Secondi et al 2003). It is always worth remembering that mixed song does not necessarily coincide with mixed genes. Any apparent 'mockingbird' in the Netherlands for example, with an unusually fast song is worth a proper look, as it may well be a bona fide Melodious Warbler.