Evening Grosbeak on St Kilda: a Species New to Britain and Ireland N
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Evening Grosbeak on St Kilda: a species new to Britain and Ireland N. Picosgi At 10.00 hours on 26th March 1969, in the old village on Hirta, St Kilda, I heard an unfamiliar call, which I noted as a metallic 'jink'. It came from a small bird perched on a dry-stone dyke and even at a range of 200 metres, using 8 x binoculars in excellent light, I was impressed by its dumpy appearance and conspicuous white wing-patch. It soon set off strongly with an undulating flight towards the army encampment, where it perched on an overhead cable; from a range of twelve metres I saw that it had a very heavy, pale lime-green beak and a predominantly dull yellow body. It dropped down to the ground, then fluttered against a Nissen hut window while attempting to perch on the narrow ledge; shortly afterwards it landed on the bucket of a diesel truck, although the engine was running noisily and the bucket vibrating. Next it flew a short distance to a wooden landing platform, where I was able to approach within five metres and take a colour photograph; I noticed that some feathers on its crown were missing and that its body feathering was very 'loose', giving the impression that it was in poor condition. It landed on the grass, but did not feed, and then flew off through the encampment; it was not seen or heard again. In size and shape, the bird closely resembled a Hawfinch Cocco- thraustes coccothraustes. The head, nape and breast were rusty brown apart from a broad, yellow superciliary stripe (which extended around the forehead immediately above the base of the upper mandible) and a black crown (some of the feathers of which, as already noted, were missing). The back was mottled rusty brown and grey, and the belly and flanks were dull yellow. The primaries were black and the secon daries and tertials white, these forming a conspicuous patch; the rump was bright yellow and the tail black. The legs were red-brown and the heavy conical beak pale lime-green. From these details I identified the bird as a male Evening Grosbeak Hesperiphona vespertina, the first record of the species in Europe, and this was afterwards con firmed by the colour photograph. The adult male Evening Grosbeak cannot be mistaken for any other species; the first-winter male can usually be distinguished from it by black or dark inner margins to the white tertials. (The St Kilda bird, with entirely white tertials, was therefore probably an adult.) The adult female is much duller, though still unmistakable: the upper- parts are mostly smoky grey, darkest on top of the head and palest on the rump; the back of the neck is tinged with greenish-yellow and the cheeks are grey (similar to the top of the head); the throat, belly and under tail-coverts are ofF-white with a dusky streak down each side of the throat; the breast and flanks are bufly grey with a tinge of yellow; the wings are mainly dull black, but the primaries (except 189 I9° Evening Grosbeak on St Kilda the three outermost) are white at the base, forming a small white patch, and the tettials are grey, edged or tipped -with white; the tail is Mack with the inner webs broadly tipped white. The juveniles resemble the female, but they are browner and their under-parts are paler and more buff with less sharply defined markings. The sexes can be distinguished even at this age: males have plain black tail- feathers, black primaries and a prominent whitish patch on the inner secondaries, while the females have a series of white spots near the tips of the rectrices, black and white primaries and no whitish area on the secondaries; also, the body colour of young males is a yellow tan and that of young females is a grey tan (Speirs 1968), The first- winter plumage follows » partial post-juvenile moult of body-feathers and wing-coverts; the juvenile flight-feathers and tail are retained, though the tertials may be shed in some cases. The first breeding plumage is assumed by abrasion, supplemented possibly by a slight spring moult about the head and neck. The adult winter plumage is produced by a complete post-nuptial moult when the bird is more than one year old (Forbush 1929, Godfrey 1966). HesperipJbm is one of two endemic New World genera of the sub family Cardueiinae in the family Fringillidae. According to Vaurie (1964), of the three Old World genera of finches with massive bills (pmeotbramttSy B&pktm and Mjvembas), Hesperiphna is roost closely related to and weakly differentiated from Eopbom—the Masked Hawfinch E. pmonata and the Black-tailed Hawfinch E, migratoria~oi eastern Asia. Although Vaurie referred to two species of Bespmpfaaa-, most authors regard them as subspecies—the darker, western H. P. brooksi and the fighter, eastern H, -p. pesperima. H, v, brmhsi breeds in western North America from the mountains of Canada to Mexico (though some authors distinguish the Mexican population as a third race H. v. mmtmd). In winter it descends to the lowkods and.is characterised by .both erratic local and general migratory movements; the pattern of its winter occurrences varies, therefore, from year to year (Nichols 1936, jewett et al, 1955). H, P. vespertma, which was formerly regarded as a bird of central Canada, was first recorded in the eastern part of the Great Lakes region at Toronto in 1854. Fol lowing an increasing number of records in Indiana between 1876 and 1887, and then in western Kentucky and New York in the latter year, there was a great eastward migration in winter 1889/90 in which some individuals penetrated to the coast of Massachusetts (Forbush 1929, Speirs 1968), Another big movement occurred in winter 1910/11 and thereafter the species was observed in New England every year. Presumably as a result of these irruptions, the still increasing summer range has now spread down into northern Michigan and as far east as Cape Breton Island, Nova Scotia. The species winters within much of its breeding area and erratically south and east to Missouri, Kentucky, Ohio, Virginia (rarely) and New England (Nichols 1936, Peterson 1947, Godfrey 1966), Evening Grosbeak on St Kilda ' In winter 1968/69, immediately preceding my observation on St Kilda, a quite unprecedented movement occurred and Dr I. C. T. Nisbet stated {in lift, to Dr J. T. R. Sharrock) that Evening Grosbeaks were more numerous than ever before in eastern North America. Some idea of the scale of this movement may be gained from the regional reports in Audubon Field Notes (June 1969) (see over): Nova Scotia Sensational numbers Newfoundland Remarkable numbers New Brunswick Much greater numbers than usual New England Almost universally abundant in early winter Quebec Major movement New York and Connecticut Generally distributed October to January New Jersey and Virginia Unquestionably the best year yet North Carolina—Georgia Tremendous numbers throughout Florida Thousands (no previous records of the species) The northward return continued to early May, which is unusually late {Audubon Field Notes, August 1969). Evening Grosbeaks feed mainly on the buds and seeds of many deciduous trees, in particular the Manitoba maple Acer negundo. Taverner (1934) suggested that the planting of this tree in many parts of Canada might affect the migratory habits of these birds. In winter they eat the seeds and fruit of a wide variety of other trees and shrubs, and at feeding stations (bird tables) their favourites are sunflower seeds. In summer they also take a proportion of animal food, particularly beetles and caterpillars (Gabrielson 1924). What is known about the breeding of the Evening Grosbeak has been summarised by Speirs (1968). The eastern race is a late nester, occasionally starting to build in late May, but usually not laying until June or even July; even the more southerly western form often does not nest until June, although eggs have been found in the first half of May and even in late April. The species breeds in coniferous, deciduous and mixed woodland, and nests have been recorded at a variety of heights from six to 125 feet in such trees as balsam fir, Douglas fir, spruce, pine, white cedar, willow, poplar, birch, elm, juneberry and maple. The nest is frequently out on a horizontal limb, but also sometimes in a fork close to or in the main trunk, particularly when near the top of the tree. Built by the female alone, accompanied by the male, it is a rather loose structure of twigs broken off in the bird's bill; these are taken both from deciduous trees and, particularly the smaller inner ones, from conifers. Usually a little moss or beard lichen Usnea is woven in, and the whole structure is then lined with fine hair-like rootlets, shreds of bark, grass fibres and dead threads of lichen; the oval cup is 80 to 95 mm across. Two to five eggs are laid, but the usual clutch is three or four, and these are blue-grey, blue or bright blue-green (becoming paler and greener during incu bation) blotched and spotted, particularly at the larger end, with various shades of olive, brown and grey and sometimes pencilled with 192 Evening Grosbeak on St Kilda black. The female alone incubates, perhaps beginning with the second egg, for eleven to 14 days. Both sexes feed the young, which spend 13 or 14 days in the nest. There may sometimes be two broods. Mountfort (1957) noted that the eggs and nestling down are very similar to those of the Hawfinch.