Grey-cheeked Thrush
Catharus minimus (Lafresnaye, 1848) (0, 1)
Photo © KG Webb - Rocky Hills, St Mary’s, Isles of Scilly, November 2023
STATUS
Nearctic and Eastern Palearctic. Polytypic.
OVERVIEW
Unfortunately, there was much overlap in measurements of this individual and it could not be racially assigned. The weak racial differences have resulted in some authorities treating it as monotypic.
Just the one record in this period, as per BOU (1971).
1950-57 RECORD
1). 1953 Fair Isle Observatory, first-winter, 5th to 6th October, trapped 5th October.
(K. Williamson, Fair Isle Bird Observatory Bulletin 2: 3-8, 134; K. Williamson, Scottish Naturalist 66: 18-20; K. Williamson, British Birds 47: 266-267, plate 47; E. V. Baxter, Scottish Naturalist 67: 100; BOURC (1956), Ibis 98: 155; I. C. T. Nisbet, British Birds 56: 204-217).
History K. Williamson (1954) in British Birds, Vol. XLVII. pp. 266-267, says: 'The occurrence of a Gray-cheeked Thrush (Hylocichla minima) at Fair Isle on October 5th, 1953, has already been recorded in detail by the writer (1954 a and b), but in view of the "national" importance of this first record for the British Isles a brief description of the bird and some other comments are repeated here.
The credit for capturing the bird belongs to Mr. William Eunson of Fair Isle, who saw it feeding in front of the Observatory Trap in the late afternoon. With the aid of Peterson (1947) I identified it as the Gray-cheeked Thrush on the evidence of its dark grey loral region and ear-coverts and the indistinct eye-rim.
As there is also in North America a sibling species, the Olive-backed Thrush (Hylocichla ustulata), in which the lores and eye-rim are buff, I decided to keep the bird overnight in one of the roosting-boxes and make identification doubly sure.
Since there was no taxonomic literature concerning American birds in our library I telephoned to Professor V. C. Wynne-Edwards, who very kindly gave me additional information, including weights and measurements, from works in his possession.
Being completely satisfied with the identification as H. minima I released the bird next morning, after checking the measurements and assisting Mr. Harry A. Craw to photograph it (see plate 47, upper).
A full description of the plumage and wing structure is given in the papers already referred to. It will suffice here to say that the bird was a dwarf thrush, hardly bigger than a Wheatear (Oenanthe oenanthe), with the upper-parts a uniform olive-brown colour - more greenish-olive than in the British thrushes and nearer the colour of a Robin, but darker. The under-parts were white except on the breast, which was suffused with buff and heavily spotted with black. I should like to emphasise the buffish tone of the breast, since the only British bird-identification book yet dealing with this species (Peterson et al., 1954) considers the absence of buff a diagnostic character. Certainly specimens of H. ustulata show a deeper colour, but examples of minima in the British Museum and Colonel R. Meinertzhagen's collections have buffish breasts and this is apparently characteristic of the Newfoundland population (Peters and Burleigh, 1951).
The Fair Isle bird was in its first winter, having white spots at the tips of the greater coverts and the innermost and second tertials. The chord of wing measured 99mm., tail 68mm., bill from skull 15mm., and tarsus 28mm. Its weight soon after capture was 24.92gm., but overnight loss reduced this to 21.60gm.
Professor Wynne-Edwards gave me 30-33gm. as the normal weight of autumn migrants in eastern North America. A larva of an American tick, Haemophysalis leporis palustris Packard, was taken from the bird's chin and was identified by Dr. Owen Evans and Mr. E. Browning of the British Museum (Nat. Hist.), where the specimen - the first recorded in Britain - is deposited....Bicknell's Thrush is the smaller of the two, but there is a considerable overlap in measurements and the Fair Isle bird cannot be assigned to either race....The weather situation on the eastern seaboard of North America immediately prior to the occurrence of this thrush was similar in many respects to that which preceded the arrival of the American Robin (Turdus migratorius) at Lundy in late October, 1952 (Davis, 1953).
A discussion of this aspect of the present record and of other American birds about the same time has already appeared (Williamson, 1954 b).'
E. V. Baxter (1955) in the Scottish Naturalist, Vol. LXVII. p. 100, under 'Review of Ornithological Changes in Scotland in 1953', admits this as the first for Scotland.
Admitted nationally in their First Report as the first for Britain (BOURC (1956) Ibis 98: 155).
