Blyth's Reed WarblerAcrocephalus dumetorum Kyzyl-Kol, Zhanatas, Kazakhstan, 10 September 2009 (René Pop).

Blyth's Reed Warbler

Finnish birders have a simple test to separate Blyth’s Reed Warbler from Marsh Warbler. If they can name the bird being imitated it's a Blyth’s Reed, but if they are tripping over their tongue because the imitations are delivered so fast and changed so frequently it’s a Marsh. Returning to lyrics of contemporary songs I imagine that if a Blyth’s Reed was talking to a Marsh Warbler it would explain its style a bit like Leonard Cohen’s in his lyrics for Slow.

I always liked it slow
I never liked it fast
with you it’s got to go
with me it's got to last

When a Blyth’s Reed Warbler sings on its breeding territory, the song has a steady pace and sounds relatively slow. It contains plenty of mimicry, but imitates a given species at length, giving us plenty of time to recognize the species. There are none of the hysterical outbursts that characterise Marsh Warbler songs.

Listen to this Blyth’s Reed Warbler song and relax into its short cycles of one, two, three or more elements, repeated generally in the same order but with small variations. The thing that makes Blyth’s song sound slow and steady is the length of these cycles and consequent slow repetition rate. Checking songs from eight different individuals, we found lengths from 1 to 2.8 s, with a mean of 1.8 s. Considering that each cycle of no more than a few imitations is generally repeated anything from two to more than 10 times (equivalent to roughly 3.6 - >18 s), the rate of replacement of material in the song is really rather slow. In a similar length of time, a Marsh Warbler could list quite a few of the bird it heard on its way to southern Africa last autumn.

Blyth's Reed Warbler Acrocephalus dumetorum Kolarevo biological station, Tomsk, Russia, 04:39, 4 July 2011 (Arnoud B van den Berg). Characteristic slow song of a bird on its breeding territory. Background: Common Cuckoo Cuculus canorus and Siberian Blue Robin Larvivora cyane. 110704.AB.043936.21

Blyth’s Reed Warblers like to include frequent short notes – eg, tak, plik and chuk – similar in length to their own tak call, but not necessarily the same. These show as vertical lines in sonagrams. They also like to include whistles which may be relatively flat, or only have simple inflections. An ultratypical motif of Blyth’s is when one of their cycles consists of a rising or descending series of such whistles, sounding like a musical scale or a fragment or an extremely simple tune, usually followed by a couple of short tak- or chip-type sounds. The whistles tend to look like short horizontal lines in a sonagram and in combination with the tak-type sounds, this creates sonagrams with a lot of flattish or sloping lines roughly alternating with clusters of vertical lines.

Only a small proportion of Blyth's imitations appear to be of Indian bird sounds, although we could easily be missing some. Many more are from Europe or share a similar migration route and wintering area, such as Red-breasted Flycatcher Ficedula parva, or are species that reside somewhere along the route, such as Graceful Prinia Prinia gracilis.

Blyth's Reed Warbler Acrocephalus dumetorum Musko, Pohjois-Karjala, Finland, 10 July 2003 (Dick Forsman). Song with imitations of northern European sounds such as Common Rosefinch Erythrina erythrina song (0:02-0:07), Yellowhammer Emberiza citrinella calls (0:09), Mealy Redpoll Acanthis flammea calls (0:10-0:11), Great Tit Parus major song (0:11), Tree Sparrow Passer montanus and White Wagtail Motacilla alba flight calls (0:12). 03.004.DF.04847.11

Blyth's Reed Warbler Acrocephalus dumetorum Voorschoten, Zuid-Holland, Netherlands, 04:06, 9 June 2020 (Arnoud B van den Berg). First of two excerpts of the same individual's song, with imitation of two harsh units of Graceful Prinia Prinia gracilis song at 0:04, likely heard on migration or while overwintering in the Indian subcontinent. 200609.AB.040600.01

Blyth's Reed Warbler Acrocephalus dumetorum Voorschoten, Zuid-Holland, Netherlands, 04:18, 9 June 2020 (Arnoud B van den Berg). Second of two excerpts of the same individual's song, with imitation of Red-breasted Flycatcher Ficedula parva rattles (0:02-0:07), likely heard on migration or while overwintering in the Indian subcontinent. 200609.AB.041813.00

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