Paddyfield Warbler
Acrocephalus agricola (Jerdon, 1845) (1, 1)
Photo © George Gay - North Ronaldsay, Orkney, 5 September 2014
STATUS
Palearctic. Polytypic.
OVERVIEW
Records as per BOU (1971).
RECORD
1). 1925 Fair Isle No locality, male, seen, 26th September; presumed same, shot, 1st October, now at National Museums of Scotland (NMSZ 1925.167).
(J. H. Stenhouse, Scottish Naturalist 45: 173-174; E. V. Baxter & L. J. Rintoul, Scottish Naturalist 46: 71; H. F. Witherby, British Birds 20: 12-14; BOURC (1927), Ibis 69: 310-311; J. A. Stout, Fair Isle Bird Observatory Report 1999: 23).
History J. H. Stenhouse (1925) in the Scottish Naturalist, Vol. XLV. pp. 173-174, says: 'At Fair Isle this year, a male example of this Reed Warbler was brought to me on 1st October. It had been obtained that afternoon by Mr. George Stout, who found it in a field of turnips. In its behaviour it was very elusive and secretive, and it was only secured by him after a long and persistent chase. There is no doubt as to its identity with a bird seen by his son, James Stout, and myself on 26th September in another patch of turnips. We pursued it for some time but had finally to give it up as lost. It probably had arrived that day; there had been a little east wind during the previous night.
In the flesh the measurements (in millimetres) were as follows: - Wing, 57; Tarsus, 20.5; Tail, 52; Bill, from feathers, 9; from gape, 12. The legs and feet were very pale brown; the bill dark horn above, pale below; the iris grey brown, and the inside of the mouth pale flesh. This is the first recorded occurrence of this Warbler in the British Isles....In general appearance Jerdon's Reed Warbler closely resembles the Marsh Warbler (A. palustris), having the pale legs of that species, but it is a smaller bird and has a different wing structure, the 2nd primary being shorter, while the 3rd, 4th, and 5th primaries are emarginate; in palustris only the 3rd shows emargination....The specimen obtained is in all probability a bird a year old in worn dress, certainly the primaries and tail feathers have not been moulted this season. Its plumage, which is somewhat bleached, approaches that of summer birds. Authorities give the second primary as equal to the 6th or 7th, or between the 6th and 7th, or even 7th and 8th, but in this bird the second primary is somewhat longer than the 6th, and in that respect it closely agrees with a bird from Sarepta (Tring Museum). The tail is shorter than usual (authorities give the tail as about the same length as the wing), but a bird from Turkestan in the Tring Museum and another from Astrakhan in the British Museum have also short tails.
The skin was forwarded to Tring to Dr. Hartert who has examined it and confirmed the identification....The bird is now in the Royal Scottish Museum, but, the skin being badly damaged by shot, it is doubtful if it can be mounted and placed on exhibition.'
Admitted by E. V. Baxter & L. J. Rintoul (1926) in the Scottish Naturalist, Vol. XLVI, p. 71, in the annual report.
H. F. Witherby (1927) in British Birds, Vol. XX. pp. 12-14, says: 'Surgeon Rear-Admiral Stenhouse is also the discoverer of this second addition to the British List. He states (Scot. Nat., 1925, p. 173) that a male example of this species was shot by Mr. George Stout in a field of turnips at Fair Isle on October 1st, 1925. Admiral Stenhouse had seen a bird, which he considers was the same, on September 26th, and thinks that it probably arrived that day. There was a little east wind during the previous night....Admiral Stenhouse describes his specimen as having the legs and feet very pale brown, bill dark horn above, pale below, iris grey-brown, and inside of mouth pale flesh.'
Admitted nationally in the Fifth List Report as the first for Britain (BOURC (1927) Ibis 69: 310-311).
1950-57 RECORD
2). 1953 Fair Isle Brae of Restensgeo, trapped, 16th September.
(K. Williamson, Fair Isle Bird Observatory Bulletin 2: 15-18; K. Williamson, British Birds 47: 297-301; R. K. Cornwallis, British Birds 47: 425; E. V. Baxter, Scottish Naturalist 67: 103; Thom, 1986; Dymond, 1991).
History K. Williamson (1954) in British Birds, Vol. XLVII. pp. 297-301, says: 'A Paddyfield Warbler (Acrocephalus agricola) was watched and subsequently trapped at Fair Isle on the morning of September 16th, 1953. It constitutes the second record of this eastern species in the British Isles, the previous example being a male collected at Fair Isle on October 1st, 1925 (Stenhouse, 1925). The bird was observed, and later examined in the laboratory, by Misses Anthea Riddolls and Helga Hitchen, Messrs. R. J. Wightman, W. Conn, J. Webb and R. Burn, in addition to my wife and myself.
Field Observations: The bird was first seen among bracken on the Brae of Restingsgeo [sic] by Wightman and Conn: it appeared to be tired, and was loth to leave the cover, so that we were able to examine it at close quarters for a considerable time. We all found it a distinctive but very puzzling bird; in reporting it to me, Wightman described it as "a huge, exotic warbler", and this description seemed very apt. It looked at least as big as a Barred Warbler (Sylvia nisoria), with an equally long tail: its general appearance was pale reddish-brown above and sandy-buff below, and there was a very prominent cream-coloured superciliary stripe.
My own first impression was that it) must be a Great Reed Warbler (Acrocephalus arundinaceus), but the clear eye-stripe seemed to rule out this possibility. Rufous Warbler (Agrobates galactotes) was considered, but there was no white in the tail; and Gray's Grasshopper-Warbler (Locustella fasciolata) which has occurred twice in Europe, at Ushant was another possibility. Quite clearly we had to trap the bird if we were to determine its species.
Accordingly, a small Heligoland with a portable catching-box was rigged up over the bracken. The bird was driven into the trap, only to escape with ease through the f-inch mesh, which we had thought quite adequate for so large a bird. The warbler then took cover in some bracken at the base of a 3-ft. high peat-bank and we decided that our best chance of catching it was to stalk it from above the bank with the small-meshed Yeoman Net, with which we planned to drop on top of it. This unorthodox method sufficed, and when the operation was complete we were all very surprised to see how small the bird really was!
Laboratory observations: In the laboratory the bird was clearly an Acrocephalus, and the plumage details and especially the wing-formula agreed with A. agricola. There was a skin of this species and also skins of Reed, Marsh and Blyth's Reed Warblers (A. scirpaceus, palustris and dumetorum) in the collection loaned to us by Dr. A. C. Stephen of the Royal Scottish Museum, and our bird matched the first of these perfectly except that the fresh plumage was rather brighter in tone. The following data were recorded. Rounded tail of 12 feathers, the outermost 8 mm. and the penultimate pair 3.5 mm. shorter than the central pair. Iris olive (not "pale brown" as stated in The Handbook, Vol. II. p. 55). Upper mandible blackish, the lower one pale flesh but brown at the tip. Legs and feet flesh-colour, claws strong and soles yellow. We could find no ecto-parasites.
The bird weighed 11.29 gm., about the same as newly-arrived Marsh Warblers we have trapped. The wing measured 60 mm., tail 53 mm., bill from skull 13 mm. and tarsus 23 mm. The wing-formula, with the 2nd primary between the 6th and 7th, indicated the typical race (Kirghiz Steppes and central Urals east to south-west Siberia) and not one of the concinens group of more eastern races, in which the and primary is shorter than the 8th. It was ringed and released, whereupon it flew to the North Haven beach and was not seen again.
Field characters: Under the heading "Field-characters" The Handbook merely says that the Paddyfield "resembles a small Reed Warbler", and Peterson et al. (1954) say that it is "doubtfully distinguishable in the field from Reed, Blyth's Reed and Marsh Warblers". In the first place, that distinctive pale eye-stripe precludes even a momentary confusion with Reed or Marsh, and it is a much sandier-looking bird. Secondly, we were all agreed that in recording this occurrence the strongest emphasis should be laid on the fact that in the field the bird did NOT look small. Through-out the encounter we were impressed by its apparently large size, and it was not until it went through the mesh of the first net that we began to have doubts on this score. My preliminary attempts to identify the bird - all of them wide of the mark - were biased by this impression, which I now believe was due to a combination of its pale, almost sandy plumage and the dark background of exposed peat and old heather when we studied it in the open. No other bird was present for adequate size comparison.
As the Paddyfield Warbler is most likely to be found in this country as a newly-arrived drift-migrant on some exposed headland or island, with an environment perhaps not dissimilar from Fair Isle, we think it is worth while emphasising that watchers should be on guard against the possibility of a repetition of this optical illusion. We would summarise the essential field-characters by saying that it is a pale, almost sandy Reed Warbler, inclining to russet above, and with a fairly long rounded tail and a prominent pale superciliary stripe....'
