Identification of first-winter Pallas's Reed Bunting

Transcription

1 Identification of first-winter Pallas's Reed Bunting Nick Riddiford and Tony Broome Afirst-winter female Pallas's Reed Bunting Emberizapallasi on Fair Isle, Shetland, on 17th September 1981, was tentatively identified in the field. Examination of skins and a literature search were necessary, however, to determine the features diagnostic of this species in first-winter plumage. The Fair Isle bird was reported as a small, odd-looking bunting by TB, who had just been watching Reed Buntings E. schoeniclus. He immediately noted this individual as different. At times it was difficult to see in long grass, but in 30 minutes' watching it allowed sufficient views at close quarters in good light for the 20 observers present to take detailed field notes of virtually all the bird's features. Despite this, no-one was prepared confidently to name the species, though all agreed that the final identification rested between runt Reed Bunting and Pallas's Reed Bunting. Keen students of British Birds were able to confirm that the bird had several characters of Pallas's Reed Bunting, and there were clearly a number of features which were 'wrong' for Reed Bunting. One that worried observers initially was the amount of streaking on the breast, flanks and rump: far continued

2 Identification of Pallas's Reed Bunting 175 more than anyone had expected for Pallas's Reed Bunting. The bird was, however, trapped later that day, and its identity confirmed as Pallas's Reed Bunting. Field description HEAD Forehead and crown dull brown, with olive tint, finely streaked darker. Nape with grey wash, finely streaked darker (more noticeable in some lights). Supercilium creamy, slightly thinner in front of eye than behind; reached rear of ear-coverts. Eyestripe, including lores, not prominent, but slightly darker than ear-coverts (again, more prominent in certain lights). Ear-coverts bright brown, but not rusty as on Little Bunting E. pusilla. Pale spot in top rear corner of ear-coverts, visible only at veryclose range. Ear-coverts bordered on lower edge by thin blackish moustachial stripe which terminated in blackish blotch or spot at the lower rear corner of ear-coverts. Moustachial and malar stripes did not reach bill. Submoustachial stripe creamy-buff. Black malar stripe ended just short of level with rear of ear-coverts, its lower edge being sharply angled towards centre of upper breast. Malar stripes appeared almost to meet in middle of upper breast when viewed from front, being partially joined by blackish streaking of upper breast. Both malar stripes infilled, to show as two dark triangular patches on sides of throat. UNDERPARTS Chin and throat whitish, neatly bordered by malar stripes and dark breast streaks. Breast white, streaked finely but prominently blackish, closest streaking at centre of upper breast. Lower breast, belly and undertail-coverts white, undertailcoverts finely but sparsely streaked dark. Flanks whitish, with blackish streaking running down from sides of breast (streaks thinner, greyer and more widely spaced on flanks). Sides of neck finely streaked. UPPERPARTS Mantle and back pale brown with hint of grey, 'colder' in tone than that of Reed Bunting. Two pale buffish lines or 'braces' running length of mantle. Thick blackish streaking between these, and at either side, accentuated braces. Finer, less intense streaking admixed. Shorter, broken, pale scapular braces running parallel to, and outside, main braces, but far less pronounced. Rump grey: generally pale grey, but varying in paleness according to light. Rump and uppertail-coverts finely streaked black; despite their fineness, streaks stood out prominently against pale background. Tail (from above) blackish, with extensive white edgings to outermost two pairs of feathers. Central pair edged warm buff from uppertail-coverts to tip, broadest proximally (this feature evident only at close range). CLOSED WING Primaries and secondaries dark greyish, with bright rusty outer edges forming marked panel on closed wing from tip of greater coverts to about level with tertial tips. Tertials black, bordered pale buff, palest on outermost edge. Greater coverts black, with rusty outer borders, broadly tipped white to bufnsh-white. Median coverts blackish, tipped white to buffish-white. Lesser coverts cold grey-brown with fine darker markings (small patch of grey-brown approximating to lesser coverts evident at shoulder of closed wing, but, during preening, wing outstretched, fully displaying lesser coverts). BARE PARTS Eye dark, surrounded by faint pale eye-ring. Lower mandible fleshcoloured, upper mandible dark. Legs and feet fleshy pink. CALL Heard four or five times: sparrow-like 'chulp', 'chee-ulp' or 'tschee-ulp'. BEHAVIOUR On the whole, very wary. When disturbed, perched very briefly in open before dropping into long grass or open crops. Despite being wary did not display 'nervous' disposition of Reed Buntings. Did not flick wings as much as do Reed Buntings (TB noted that the Reed Buntings present did so constantly). Had habit of spreading tail when perched on fence wire, more so than when feeding on ground. Long-tailed appearance in flight. Best views obtained when bird perched on block of wood at ground level 3-5 m from observers. Hand description Once field notes had been completed, the bird was trapped and a more precise record of coloration was made as follows: HEAD Forehead and crown grey-brown, divided above ear-coverts by very thin dark edged dull buff. Neck grey. Supercilium off- brown line. Lores brown. Ear-coverts pale white, more distinct above and behind eye, ruddy brown with very dark brown spot at

3 176 Identification of Pallas's Reed Bunting Fig. 1. First-winter female Pallas's Reed Bunt ng Emberiza pallasi, Shetland, September 1981 (painting by J F. Holloway) lower rear corner. Thin black moustachial giving streaked appearance. Uppertailcoverts stripe from just before ear-covert spot forwards as lower border to ear-coverts, but fading to very indistinct at base of lower mandible. Submoustachial stripe off-white. Malar stripe arising 3 mm short of base to lower mandible, then fanning out downwards as triangular black-brown patch to join with heavy streaking on upper breast. grey, with buff-white edgings. Tail feathers: central pair grey, with chestnut edge to outer web, buff-white edge to inner web. Other feathers grey-black. Outer two same, but outermost with distal two-thirds white, apart from thin black central wedge along shaft, and second outermost with white triangular wedge on distal third of outer web. UNDERPARTS Chin and throat off-white. Upper breast heavily and densely streaked black-brown, almost merging with malar stripes to make virtual bib. Sides of breast more sparsely streaked, but heavier than flanks. Flanks sparsely streaked black, with thin short chestnut streaks on flanks/belly partition zone. Lower breast and belly offwhite, tinged in places yellowy-green (probably staining from grass). Undertailcoverts off-white, very faintly streaked brown. UNDERPARTS Mantle feathers black, narrowly edged chestnut and buff; buff aligning as braces when plumage not disarranged. Back grey-brown. Rump pale whitish-grey, with centre of individual feathers grey-black, WING FORMULA WING Lesser coverts cold olive-brown, edged grey and with grey-brown fringing to tips. Median coverts black, with well-demarcated buff-white tips about 2-3 mm broad. Greater coverts as median coverts but tippings slightly whiter, and broader on outer webs. Primary coverts and alula grey-brown, edged brown. Primaries grey, narrowly edged chestnut. Secondaries same, but broadly edged chestnut. Tertials grey, edged chestnut proximally, fading to buff-white distally, edging being uniformly broad. Underwingcoverts off-white, very faintly streaked brown. Underwing greyish-white, with very faint yellow wash. Cinnamon tinge to axillaries. * longest _J I I I _J emarginated *6.6 mm shorter than primary coverts Wing point to secondaries 12.5 mm; to tertials 7.5 mm.

4 Identification of Pallas's Reed Bunting 177 BARE PARTS Eye very dark brown. Bill: upper mandible black, lower mandible pale pink, palest towards tip. Gulmen looked very straight, from forehead to tip. Legs pale pink. leet ver Y slightly darker, MEASUREMENTS Wing 68 mm; bill 11 mm; tarsus 18 mm; tail 61 mm; weight 13.9 g (at GMT). Age, sex and race The bird was aged as a first-winter on plumage-wear features. The plumage was generally fresh, but each tail feather tapered to a marked point which was slightly worn: adults would have extremely abraded plumage if unmoulted (cf. Broad & Oddie 1980) or completely fresh plumage including rounded tail feather tips if moulted (Svensson 1975). The bird was sexed as a female on throat- and crown-feather patterning and on lesser-covert coloration (cf. Svensson 1975): the sexes are readily separable on crown and throat characters, but sexing according to lesser-covert colour is probably not reliable (Dr A. Knox in litt.). The bird was considered to show characteristics of the northern race E. p. polaris, which is darker and more markedly streaked than the southern nominate race (Dementiev & Gladkov 1954). 69. First-winter female Pallas's Reed Bunting Emberiza pallasi, Shetland, September 1981 (illustrating pointers 4, 5, 6, 8, 10, 11 & 13) (Tony Broome) Skins In early December 1981, NR visited the British Museum (Tring) to look at skins. The Museum had a large number of the nominate race, including a good series of autumn females and first-years. Unfortunately, the only two specimens allocated to the northern race E. p. polaris were both breeding plumage adult males. One feature which stood out immediately was the rump, which was warm buff streaked darker on all females and immatures in the collection, not the whitish-grey of our bird. All other characters of the first-years, however, which were easily separated from adult females by the

5 178 Identification of Pallas's Reed Bunting 70. First-winter female Pallas's Reed Bunting Emberiza pallasi, Shetland, September 1981 (illustrating pointers 4, 5, 7, 11 & 12) (Tony Broome) presence of breast and flank streaking, were consistent with those of the Fair Isle individual. Discussion Despite the amount of streaking on upper breast and flanks, the Fair Isle individual was not as difficult to identify as we first feared. This plumage type is well described by Dementiev & Gladkov (1954), while other plumages described include spring and summer adult male and female (Kitson 1979), autumn adult female (Broad & Oddie 1980) and juvenile (Kitson 1980). Dementiev & Gladkov (1954) stated that the plumage of first-years is even more strongly marked with blackish-brown streaks after the post-juvenile body moult. Kitson's reference to streaks being finer and more widely spaced than those of Reed Bunting, and his accompanying sketch (Kitson 1980), relate to individuals in juvenile plumage prior to the post-juvenile head and body moult. This explains the discrepancy between his birds and our individual. It is evident, therefore, that the literature adequately describes the species in all its plumages. But a considerable amount of searching in a variety of publications is necessary to piece together the various plumages. It also required research to isolate those features which were peculiar to first-winter birds of this species. The two species with which Pallas's Reed Bunting is most liable to be confused are Reed Bunting and Little Bunting, so we concentrated on criteria separating first-winter Pallas's Reed Bunting from similar plumage types of these two congeners. Superficially, the Fair Isle bird resembled an autumn Reed Bunting, but was obviously smaller: this was confirmed by reference to the four or five Reed Buntings present that day and to the dozen or so Twites Carduelisjlapirostris with which it kept loose company and which it matched in size. It was clearly not a Little Bunting, despite its similar size, differing from that species most notably in the lack of rich chestnut cheeks, lack of marked and contrasting head pattern, the triangular malar patches and semi-bib appearance, the extent and intensity of dark marking

6 Identification of Pallas's Reed Bunting First-winter female Pallas's Reed Bunting Emberiza pallasi, Shetland, September 1981 (illustrating pointers 4, 5, 6, 8, 10, 12, 13 & 14) (Elizabeth Riddijord) at the rear lower corner of the ear-coverts, the pale grey rump, and the distinctively sparrow-like call. The bill, too, seemed heavier and more reminiscent of Reed Bunting, though the culmen was straight, indeed straighter than on many Little Buntings, which have a slightly concave culmen. We considered the possibility of runt Reed Bunting, but again several features were inconsistent with that species. The proportions were wrong: this bird seemed long-tailed, especially in flight, when its proportions were reminiscent of the accompanying Twites. The culmen was straight, giving the bird a quite distinctive profile. The head lacked the contrasted pattern of Reed Bunting; not only are a Reed Bunting's supercilia accentuated by the warm chestnut brown tone to the crown, but they are also bordered above by a dark lateral stripe and below by a dark eye-stripe. This bird had the faintest of eye-stripes and a very faint lateral stripe, hence the lack of contrast. The face pattern did not appear to add up to Reed Bunting. The ear-coverts looked bright brown, with the black spot at the lower rear corner a very marked feature. The black triangular marks and associated upper breast streaking made a pattern which very few Reed Buntings show (perhaps similar in a few late autumn to early spring males?). In the field, the moustachial stripe appeared not to reach the base of the lower mandible, and the malar stripe was well short of the bill: on Reed Bunting, a well-defined moustachial stripe and usually the malar stripe reach the bill (or the latter falls only just short). The chestnut panel on the secondaries on the closed wing was far richer than is shown by Reed Bunting. The double wing-bar also stood out far more than on any Reed Bunting, due to the individual greater and median covert coloration. On Pallas's Reed Bunt-

7 180 Identification of Pallas's Reed Bunting 72. First-winter female Pallas's Reed Bunting Emberiza pallasi, Shetland, September 1981 (illustrating pointers 8, 9 & 13) (Elizabeth Riddiford) ing, the black centres of the individual feathers accentuate the buff-white tips, while on Reed Bunting the greater and median coverts are brownblack centred and tipped brown-buff, giving very poorly demarcated wingbars. The very pale grey rump was another feature more accentuated than on Reed Bunting. Finally, when the bird preened and displayed a set of cold grey-brown lesser coverts (not chestnut-brown as on Reed, cf. Svensson 1975), and uttered a sparrow-like 'chee-ulp' or 'tschee-ulp', quite unlike any bunting call we had heard before, it was clear that its identity was other than runt Reed Bunting. Conclusion Based on our experience of this individual and comparative examination of skins, we were able to draw up a set of criteria to separate this species from Little and Reed Buntings in the field. We have excluded a few characters present.but not obvious in the field: for instance, the thin and sparse chestnut streaking on the flanks, noted in the hand on our individual and shared by the BM specimens. Equally, characters considered too subjective or variable such as the intensity of black streaking on the upperparts have been omitted. We consider that the following are the main pointers to the identification

8 Identification of Pallas's Reed Bunting 181 of first-winter Pallas's Reed Bunting; they are listed in approximate order of significance (see plates 69-72): 1. Sparrow-like'chee-ulp'call 2. Small size 3. Long-tailed appearance 4. Bright brown ear-coverts, with conspicuous black or blackish-brown spot at lower rear corner 5. Cold olive-brown or grey lesser coverts 6. Straight culmen 7. Black triangular malar stripes, joining streaking on upper breast to form virtual bib 8. Two prominent buffish-white wing-bars 9. Very pale grey rump (E.p.polaris only) 10. Cold olive-brown crown and poorly defined supercilium, thus lacking contrasted head pattern of Reed Bunting 1 1. Prominent chestnut panel on closed wing 12. Malar stripe not reaching bill 13. Grey nape 14. Bare parts flesh coloured 15. Undertail-coverts finely streaked Thus, call may well draw an observer to a bird in flight or on the ground, while the majority of other features are readily seen only when the bird is on the ground. The first eight pointers taken in conjunction are diagnostic. It should be borne in mind, however, that 'small size' and 'long-tailed' are subjective, the species' repertoire of calls will probably extend beyond a mere sparrow-like 'chee-ulp' (in fact TB noted that the bird gave a quiet 'sip sip' call when first flushed), while the lesser coverts are frequently very difficult to see in the field. Also, occasional Reed Buntings may show one or other of the features (though never all), such as black triangular malar stripes (on males approaching breeding plumage when, however, other male Reed Bunting features will show), and obvious wing-bars, though never nearly so prominent nor so white. Pointers 9 to 15 are questions of degree and can be displayed by Reed Bunting in the field. Thus, Reed Bunting shows a chestnut wing panel which, however, is never so marked as on Pallas's Reed Bunting. These lower-order pointers should, therefore, never be used as aids to identification in the absence of pointers 1 to 8, but act as useful supplementary characters when assessing an individual in the field. Finally, a word of warning. Whilst it is our opinion that the above pointers will suffice to identify a first-year Pallas's Reed Bunting in autumn, we stress that great care should be taken to use a combination of these criteria and not to rely for identification on only one or two characters. Acknowledgments We should like to thank Derek Reid lor arranging access to skins at the British Museum; Dr Alan Knox for checking further points there for us;.john F. Holloway for the use of his

9 182 Identification of Pallas's Reed Bunting painting; and all watchers of the Fair Isle bird for useful comments on plumage features. Thanks, too, are due to Peter Grant lor comments on, and improvements to, the text. Summary An account is given of the occurrence of a first-winter female Pallas's Reed Bunting Emberiza pallasi, probably of the northern race E. p. polaris, on Fair Isle, Shetland, in September 1981, with detailed field and hand descriptions. As a result of field experience, a literature review and skin examination, a list of 15 pointers is presented for the identification of first-winter Pallas's Reed Buntings; pointers 1-8 are considered diagnostic and 9-15 supplementary, but it is stressed that criteria should be used in combination rather than in isolation. References BROAD, R. A., & ODDIE, VV. E Pallas's Reed Bunting: new to Britain and Ireland. Brit. Birds 73: DEMENTIEV, G. P., & GLADKOV, N. A. (eds.). 1954, translated The Birds of the Soviet Union. vol. 5. Israel Program for Scientific Translations, Jerusalem. KITSON, A. R Identification of Olive-backed Pipit, Blvth's Pipit and Pallas's Reed Bunting. Brit. Birds 72: Further notes from Mongolia. Brit. Birds 73: SVENSSON, L Identification Guide to European Passerines. 2nd edn. Stockholm. Nick Riddiford and Tony Broome, Fair Isle Bird Observatory, Fair Isle, Shetland