Western Bonelli's Warbler
Phylloscopus bonelli (Vieillot, 1819) (1, 1)
Photo © Richard Brown - Skokholm, Pembrokeshire, 24 September 2017
STATUS
Western Palearctic. Monotypic.
OVERVIEW
Formerly treated with Eastern Bonelli's Warbler P. orientalis as a single species Bonelli's Warbler. It was in 1997 that the BOURC (Ibis 139: 198) took the advice of a number of people and separated Bonelli's Warbler into two species, Eastern and Western.
There are just two records for the period.
RECORD
1). 1948 Pembrokeshire Skokholm, female, trapped and killed, 31st August.
(P. J. Conder & J. Keighley, Skokholm Bird Observatory Report 1948: 12; P. J. Conder & J. Keighley, British Birds 42: 215-216; C. P. H. Grant, Bulletin of the British Ornithologists' Club 69: 46; BOURC (1950), Ibis 92: 139; Sharrock & Grant, 1982; Lovegrove, Williams & Williams, 1994; M. J. Rogers and the Rarities Committee, British Birds 91: 122-123).
History P. J. Conder & Joan Keighley (1949) in British Birds, Vol. XLII. pp. 215-216, say: 'At 19.30 B.S.T. on August 31st, 1948, a warbler, was caught in the Garden trap on Skokholm Island, Pembrokeshire. After a long examination that evening and again on the following morning it was decided to kill the bird. The specimen was sent to Mr. R. Wagstaffe, Director of the Yorkshire Museum, who identified it as a female Bonelli's Warbler (Phylloscopus bonelli). Very little was seen of the bird in the field before it was caught, but J.K. records that the rump and tail were noticeably yellowish green, and that the white under-parts, grey head, and pale legs were also striking when seen from about two or three yards. It called "hooeet" once or twice when flying into the trap. This is the first record of this species in Great Britain.
Mr. Wagstaffe, in his report to the List Committee of the British Ornithologists' Union on December 15th, 1948, states that, after having examined a large series of Ph. b. bonelli Vieillot, and Ph. b. orientalis Brehm, he came to the conclusion that the specimen matched more closely the majority of specimens of orientalis in coloration, but that the wing measurement 60.5 mm., with the primaries straightened - the method used by Ticehurst - was smaller than the average wing measurement recorded by that authority in his Genus Phylloscopus. Moreover, the 2nd primary fell between the 6th and 7th primaries. This is an almost 80 per cent characteristic of bonelli, as against a 2 per cent characteristic of orientalis. "Nevertheless, it could be argued, on the basis of pure taxonomics", said Mr. Wagstaffe, "that the bird is still assignable to orientalis, but as I have been unable to find an undoubted specimen of orientalis with wing as small as 60.5 mm., and of wing formula 2 = 6/7. I am prepared to believe, for the time being at least, that the bird is probably, but by no means certainly, a specimen of bonelli bonelli".
In this belief he was partly influenced by the geographical distributions of the two forms and by the fact that some examples of the typical race are much greyer than others.
At the previous meeting of the Committee it had been suggested that the first example of any addition to the British List should be treated binomially until such time as subspecific assessment could be based on more than one specimen. This was agreed to in the present case.'
C. P. H. Grant, Editor (1949) in the Bulletin of the British Ornithologists' Club, Vol. LXIX. p. 46, at the 483rd Meeting of the Club held on 16th February 1947 at the Rembrandt Hotel, London, says: 'Mr. R. Wagstaffe exhibited the specimen obtained on Skokholm Island by Mr. Peter Condor [sic].'
Admitted nationally in their twenty-first Report (BOURC (1950) Ibis, 92: 139).
1950-57 RECORD
2). 1955 Dorset Culverwell, Portland Bill, trapped, 29th August.
(W. H. Tucker, British Birds 48: 551-552; K. B. Rooke, Proceedings of the Dorset Natural History and Antiquarian Society 77: 74; M. J. Rogers and the Rarities Committee, British Birds 91: 122-123; J. S. Ash, Fair Isle Bird Observatory Bulletin 3: 91; Prendergast & Boys, 1983).
History W. H. Tucker (1955) in British Birds, Vol. XLVIII. pp. 551-552, says: 'At 09.35 G.M.T. on 29th August 1955, a small warbler was caught in one of the Heligoland traps at Portland Bill, Dorset. At first its identification was not at all clear, but eventually it was identified as a Bonelli's Warbler (Phylloscopus bonelli). Detailed descriptions were made independently by Messrs. K. V. Edwards and Alan Till, who kindly came and examined the bird, and by myself. When the time came to release the bird, it was allowed to find its way out of a small cage into a bramble bush. Here it was possible to watch it feeding and taking short flights. Later in the same day the bird was found on a barbed-wire fence several hundred yards away and was watched in the evening sunlight catching insects in a fashion similar to that of the commoner Phylloscopi, It is considered unnecessary to mention the account of the plumage made when the bird was examined in the hand, as this is only a more detailed record of the field-description.
Full supporting evidence, however, has been submitted to the Editors. Laboratory description. Weight at time of capture, 7.4 gm. Wing formula: 3rd to 5th primaries emarginate; 3rd longest; 2nd, 5 mm. shorter (approx. = 6th); 4th, 1 mm. shorter ( = 5th); 6th, 4 mm. shorter. Wing length, 65.5 mm. (straight and flattened). Legs, brownish-horn (or dark horn), darker than those of Willow Warblers (Ph. trochilus) trapped about that time. Iris, very dark brown (or black with slight reddish tinge); pupil, black. Field description. Sides and all top of head and mantle, a smooth greyish-brown. The greenish tinge noticeable in the hand was hardly discernible in the field. A greenish-yellow patch on the wing was very marked, formed by the edgings to the primaries and secondaries. The yellowish rump was more obvious in the field than in the hand, especially when the bird raised its wings or took short flights. The whole of the under-parts was a pale dirty-grey white, lacking any tinge of yellow or brown except at the vent and under tail-coverts, which were of a warmer shade.
The call note sounded like "hu-eet" in the cage; in the field it was considered not to be quite so drawn out as that of Willow Warbler or Chiffchaff (Ph. collybita). The date (29th August) of the occurrence of this bird, the third British specimen, is interesting in being so close to the time of the year of the two previous records (Skokholm, 31st August 1948; and Lundy, 1st September 1954).'
Comment The 1954 Lundy record has been found to be indeterminate.
