Portland Bird Observatory
and Field Centre
Blyth's Reed Warbler Acrocephalus dumetorum
There have been three records of Blyth's Reed Warbler at Portland:
| The occurrences of Blyth's Reed Warbler at Portland | |
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2001 - November 12th, a first-year bird trapped and ringed at the Bird Observatory.
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© Martin Cade |
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2001 - October 16th to November 3rd, a first-year bird trapped and ringed at the Bird Observatory.
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© Martin Cade |
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1989 - June 12th, one trapped and ringed at the Bird Observatory.
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© Martin Cade |
Biometrics and wing-formula details noted for the three birds were as follows:
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12-06-1989 | 16-10-2001 |
12-11-2001 |
dumetorum range |
| Wing length (maximum chord) | 62 | 66 | 65 | 58-65 |
| Tail length | 52 | 56 | 54 | 48-54 |
| Bill length (to skull) | 17 | 16 | 17 | 15.3-17.6 |
| Emarginations | P3 and P4 | P3 and P4 | P3 and P4 | P3 and P4 |
| Notches | P2 | P2 and P3 | P2 and P3 | P2 and P3 |
| 2nd primary < tip of wing (and position) | 4 (P5/P6) | 7 (P6/P7) | 4.5 (P5/P6) | 3.5-6.5 |
| 1st secondary < tip of wing | 13 | 18 | 15.5 | 11.5-16 |
Measurements in mm; primaries numbered ascendently.
The identification of the second bird - the individual present from October 16th to November 3rd 2001 - was problematic since a number of its biometrics fell outside the range expected for Blyth's Reed Warbler. Expert opinion as to its identification was sought from a number of sources:
Lars Svensson (pers. comm.) commented on the plumage and biometrics as follows:
You have three
possibilities:
(1) A very large Blyth's Reed Warbler, 1yr.
(2) An eastern Reed Warbler fuscus.
(3) A hybrid Blyth's Reed and Marsh Warbler.
It is very difficult to say which is most plausible. I would probably leave it
unidentified myself. Actually, the third possibility is quite likely. I think
the shortish-looking bill fits with this theory, too. If it is not, it is a
very large Blyth's Reed after all. fuscus is not known to have more than a
hint of an emargination on P4, and none on P5, so this possibility is quite
far-fetched.
Mark Constantine (pers. comm.) commented on the vocalisations as follows:
The calls are good for Blyth's Reed Warbler and poor for Marsh Warbler and Reed Warbler. I recorded two types of call, the first is a simple 'zeck' note and the second is an alarm used for a Sparrowhawk and when approaching Chiffchaffs nearby. I compared them with recordings of Blyth's Reed Warbler made by Magnus Robb in spring 2000 in Kazakhstan, and Killian Mullarney in November 2001 in Goa. I also compared the notes to similar calls by Marsh Warbler and Reed Warbler: they sounded different and the sonograms didn't compare favourably.
Sonograms of 'zeck' call for Portland bird (left), Blyth's Reed Warbler (centre) and Marsh Warbler (right).
Sonograms of alarm call for Portland bird (left), Blyth's Reed Warbler (centre left), Reed Warbler (centre right) and Marsh Warbler (right).
A number of feathers from the bird, together with some feathers from the individual trapped on 12th November 2002, were submitted for mtDNA analysis to Dr David Parkin of the Institute of Genetics, Queen's Medical Centre, Nottingham. Dr Parkin (pers.comm) commented as follows:
Both birds were
Blyth's Reed Warblers - or at least their mothers were! The gene that we
sequenced is transmitted from mother to offspring, so that the male plays no
part. Thus either the birds were Blyth's Reed or hybrids. If hybrids, then the
mother was a Blyth's Reed Warbler.
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