Mark's Articles
9 - In your dreams (continued)
Eurasian Reed WarblerAcrocephalus scirpaceus Texel, Noord-Holland, Netherlands, 7 June 2015 (René Pop).
Eurasian Reed Warbler
In the illustrious company of Marsh Warbler and Blyth's Reed Warbler, the song of Eurasian Reed Warbler seems very modest indeed. It has little of the dynamism and brilliant mimicry of Marsh, nor the musicality of Blyth's Reed. Indeed, one of the best ways to recognise Eurasian Reed's song is its sheer monotony as it just bonks steadily away.
In Britain I’ve spent quite a lot of time explaining the differences between Eurasian Reed Warbler and Sedge Warbler A schoenobaenus song to novices over the years. Many seem to find it helpful when I say they embody reason and passion. Sedge is higher pitched and more excitable than Reed, surging in great waves of passion accompanied by song flights. Meanwhile, Reed's song to me is like your conscience and as steady as your reason. Musically it's as regular and predictable as the gorilla's drum solo in Phil Collins' In the air tonight.
As always when you listen with more care, bonking away is a bit unkind, and that isn’t quite how it works in practice. Eurasian Reed Warblers make their songs from around 200 discrete units a minute delivered at 3-4 per second. The units are seldom just a single, simple sound, but more often a rapidly doubled harsh sound, a short rattle, a whine, two contrasting sounds one immediately following the other, etc. These are essentially brief units of repetition, and each one is repeated on an average of three times. Two, three or four repetitions are usual, but anything from one to eight can be expected. A change from one set of repeated units to the next takes place on average just over once a second.
Eurasian Reed Warbler Acrocephalus scirpaceus Nieuwedijk, Utrecht, Netherlands, 03:58, 10 June 2011 (Arnoud B van den Berg). Typical song at close range just before 04:00 in the morning. Background: Greylag Goose Anser anser, Common Cuckoo Cuculus canorus and Common Reed Bunting Emberiza schoeniclus. 110610.AB.035800.01
In being made up of thrice repeated motifs, Eurasian Reed Warbler's song could be compared to that of a Song Thrush Turdus philomelos. But why does it strike us as so much less beautiful? Apart from its monotonous pace, contrasting with the more dramatic rhythms of Song Thrushes, much of this is due to the timbre of the song. As a species that spends most of its life in dense vegetation, Eurasian Reed needs to sing songs that propagate in an environment where most passerine songs would be muffled and lost. Think about it. Reedbeds are challenging acoustic surroundings, where higher frequency sounds (smaller wavelengths) bounce off vegetation, and swishing reeds will mask short and varied sounds. Are there any birds that sing low down in the reeds and have intricate, melodic songs? No, this is the world of booming Eurasian Bitterns Botaurus stellaris and Little Bitterns Ixobrychus minutus, similarly low-pitched and repetitive Common Cuckoos Cuculus canorus and ultra-monotonous Savi's Warblers Locustella luscinioides, not to mention lots of frogs. Eurasian Reed adapt to this environment in the same ways as the other creatures, by building a lot of redundancy or repetition into their songs, and by singing at as low a pitch as their small body can manage. Perhaps most strikingly, they prefer harsh, guttural, churring sounds. Such sounds cover a wide frequency range, employing many wavelengths at the same time, making it likely that at least some part of each sound will penetrate the stalks and blades of the reedbed.
Eurasian Reed Warbler Acrocephalus scirpaceus Polgár, Northern Great Plain, Hungary, 04:13, 11 May 2019 (Magnus Robb). Song of several males in a ditch. Background: Greylag Goose Anser anser, Eurasian Bittern Botaurus stellaris, Little Bittern Ixobrychus minutus, Black-crowned Night Heron Nycticorax nycticorax and Common Cuckoo Cuculus canorus. 190511.MR.041337.01
Eurasian Reed Warblers actually have far more variety in their songs than we often realise. Males may have 90 different types of units, for example, and they mimic other species much more often than they are given credit for. However, compared to Marsh Warblers, their imitations seem less perfect, and this may be partly why people don't notice. Another reason is that they don't seem to use mimicry for dramatic effect but just as a source of the kind of sounds they like. So, you can often find mimicry of various other species. There are many examples in the recording below. Who knows, perhaps they regularly include imitations of some of the sounds they hear during their winter stay in Africa, but we have not recognised any so far.
Eurasian Reed Warbler Acrocephalus scirpaceus Zwanenwater, Noord-Holland, Netherlands, 08:39, 22 May 2018 (Arnoud B van den Berg). Song full of imitations, eg, Eurasian Blue Tit Cyanistes caeruleus (0:03-0:12), Common Buzzard Buteo buteo (0:13-0:26), Bearded Reedling Panurus biarmicus (0:31-0:32 & 0:38-0:47), Common Blackbird Turdus merula (0:51-0:56) and Sedge Warbler A schoenobaenus (1:01-1:02, 1:08). Background: Greylag Goose Anser anser, Willow Warbler Phylloscopus trochilus and Eurasian Wren Troglodytes troglodytes. 180522.AB.083908.11
Talking of Africa, the taxonomy of reed warblers recently took a surprising twist. It started with the realisation that non-migratory reed warblers in Morocco have shorter wings and a different moult strategy (Amezian et al 2010). This led to the discovery that those birds are genetically distinct from Eurasian Reed Warblers and that migratory reed warblers breeding in most of Iberia belong to the same population (Olsson et al 2016). So, is this Ibero-Maghreb reed warbler more closely related to African Reed Warbler A baeticatus, which breeds as close as Senegal, or to European Reed? The question proved difficult to answer, so when the old name ambiguus was resurrected for this population, nobody argued against it. Concensus is leaning towards including this population in African Reed (eg, IOC World Bird List v 11.1, Clements checklist update 2019) giving many of us an armchair tick but causing enormous headaches in the identification department.
Magnus has had a go at separating songs of Eurasian (A s scirpaceus) and Ambiguous Reed Warblers (A b ambiguus), finding it extremely challenging. To all intents and purposes, they sound the same. Being unable to hear any difference at all at first, he started measuring song units per minute, rate of change of the song units, etc using a sample of songs of several individuals of each. In each measurement it soon became clear that there was much overlap between the two populations. The only slightly promising if ambiguous lead for further research is that by ear, the units in Ambiguous Reed Warbler song seem slightly shorter, without this affecting their speed of delivery, giving the song a slightly more choppy, 'staccato' flavour.
Ambiguous Reed Warbler Acrocephalus baeticatus ambiguus Dhyria, Oued Loukkos, Larache, Rharb, Morocco, 07:29, 8 June 2010 (Arnoud B van den Berg). Song. Background: Zitting Cisticola Cisticola juncidis. 100608.AB.072900.01
One day when he has measured a large enough sample of both species, checking the relative proportion of sound versus silence in the song, he expects that Eurasian Reed will have longer units and shorter gaps than African Reed, but only by a whisker. Another, even bigger job for his to do list is to count repertoire sizes, cataloguing all the slightly different types of units in the songs of both. Who knows, perhaps one will have a significantly larger repertoire than the other. We already know that non-migratory 'Acros' in Africa have much smaller repertories than intercontinental migrants like Eurasian Reed and Marsh Warbler. Being only a partial migrant, might ambiguus also have a smaller repertoire? For now, we can say that the songs have so far proven to be inseparable, and what we have written above about how to recognise Eurasian Reed song can safely be applied to Ambiguous Reed Warbler as well.
It's frustrating to do the analysis and not find anything and I had to twist Magnus’s arm to get him to persevere on this subject. In the end, he has contributed more on all of these warblers than me. At the time of writing, we are both stuck inside waiting for the corona pandemic to end, and spring has started. Common Blackbird T merula and Song Thrush both had a good go this morning in my garden. I don’t think the gradual change in day length has so much to do with it either. It has been terribly cold here until today and now suddenly it's mild and bingo: bird song.
As we have shown above, confident separation of Marsh Warbler, Blyth's Reed Warbler and Eurasian Reed Warbler is possible just with their songs. I have occasionally found vagrants of the next two, Melodious Warbler H polyglotta and Icterine Warbler, over the years, but the experience is never very satisfactory. Melodious in August disappear for hours and don’t make a sound as they feed on blackberries deep inside impenetrable thickets. So you'll understand why I'd prefer to find a spring bird singing. Indeed, I would dearly love to find either of them singing in spring. So I get my exceptionally long zoom stick and poke Magnus again to help me with Melodious and Icterine. After all, he will get singing Melodious on his doorstep in Portugal, and Arnoud will have Icterine singing from hedgerows not so far away from his in Holland. Let's start again with Killian and Richard‘s beautiful illustrations of both.