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Review of Irish Records of Greenish Warblers, 1984.

Killian Mullarney (on behalf of the Irish Records Panel)

The first Greenish Warbler Phylloscopus trochiloides recorded in Ireland was in 1952; within the next twenty years, however, over twenty records were accepted as being of this species. This sudden regularity was not at the time considered surprising since (1) there was evidence from northern Europe that Greenish Warbler was rapidly expanding its breeding range westwards (Valikangas 1951) and (2) field ornithology was just beginning to get off the ground in Ireland (cf. all the other former rarities which became regular from the late 1950s onwards). The great majority of Irish records was from Cape Clear Island, Co. Cork, which recorded at least one bird in nine of the twelve years between 1959 (when the Observatory was founded) and 1970, mostly in October. This trend came to an abrupt halt in the early 1970s when many observers realised that the identification criteria being used did not satisfactorily distinguish between Greenish Warbler and certain similar plumages of Chiffchaff P. collybita, notably those belonging to the Scandinavian race P. c. abietinus and the Siberian race P. c. tristis.
This paper is intended to clarify the identification of Greenish Warbler and presents the results of a recently completed review of Irish records carried out by the Irish Records Panel. The British Birds Rarities Committee is currently reviewing all British records.


Identification

Progress in the development of reliable criteria for identifying Greenish Warbler was for a time confounded by misconceptions regarding its similarity to Chiffchaff. While there are still aspects requiring more research (particularly in the context of distinguishing Greenish from some of its closest congeners, Green Warbler P. nitidus and Two-barred Greenish Warbler P. plumbeitarsus) confusion with Chiffchaff is no longer the problem it once was. The following account summarizes the characters of Greenish Warbler now considered reliable. The descriptive details relate to a typical fresh plumaged first-winter bird. Adults undergo a body moult after the breeding season (before migrating) and do not have a full moult until well after their arrival in wintering areas. Consequently their tail and wing feathers, including coverts are much worn and faded in autumn and the wing-bar is reduced or may even be absent (Williamson 1967).


Greenish Warbler in first-winter plumage

Similar to Chiffchaff in size and structure though may appear slightly smaller and shorter tailed. Upperparts uniform greyish-green to pale olive-green. Underparts white or off white, often with a faint grey wash on sides of neck and breast and a hint of yellow on the throat, axillaries (which may be visible adjacent to the bend of the wing) and undertail-coverts. Overall strikingly paler and cleaner than P. c. collybita. Conspicuous long, creamy or yellow washed supercilium, quite broad behind the eye and accentuated by the rather broad olive-green eye-stripe behind the eye and dark stripe across the lores in front. In certain positions, for example when the head is sunk in to the shoulders, the supercilium and eye-stripe may appear remarkably long and turned up towards the rear crown. Narrow pale crescent below eye. Ear coverts mainly off-white shading to greyish-green toward rear and usually not blotchy as in Arctic Warbler P. borealis. Sides of neck slightly lighter in shade than crown and mantle. Wing and tail feathers light sepia, edged more or less obviously with bright olive or yellowish-green which may form a bright panel across the remiges. Short, straight wing-bar formed by well defined whitish tips to outer four to six greater coverts. While the wing-bar may not always be an outstanding feature it is usually clearly defined and obvious. It is often slightly wedge-shaped, narrowing proximally, and examination in the hand will reveal a small extension of the white tip onto the inner webs of the outer greater coverts. Occasionally there is a trace of a second wing-bar on the median coverts. Tertials almost uniform with, and only slightly browner than, mantle, with very thin whitish tips and edges to inner webs; they tend not to be as dark-centered as in Chiffchaff. Wings comparatively short, primary-projection being about half the length of the exposed tertials with more or less equally spaced primary tips - thus, the wing structure is very similar to Chiffchaffs, even when examined in the hand (see Svennsson 1984).
Bare Parts
Bill: slight, like a Chiffchaff's (but on average slightly longer), often with a strikingly bright orange-yellow, yellowish-flesh or pinkish coloured lower mandible which may be more eye-catching in the field than when examined in the hand.
Legs: color variable, usually dark greyish-brown, sometimes quite light yellowish-brown with yellowish soles.


Voice

Greenish Warbler voice transcriptions vary widely, but many observers consider the sound to be very distinctive and an important clue to identification. The typical call is often described as clearly disyllabic "swee-lee", rather similar to the common call of White Wagtail Montacilla alba (Lars Svensson, Göran Walinder pers comm.) At least two accepted Greenish Warblers in Ireland uttered an emphatic "psleeoo" note reminiscent of both the typical flight call of Yellow Wagtail M. flava and a somewhat similar note of Pied Wagtail M. a. yarelli (pers obs.). A migrant in Kent, England in October 1982 gave this type of call, then described as a full, "slewt", sometimes disyllabic "slewslewt", often quickly repeated and on a couple of occasions running into a scratchy, weak warble, not unlike a fast version of the song of Willow Warbler P. trochilus in structure (P.J. Grant pers comm.). Lars Svensson (pers. comm.) has suggested the possibility that adults may stress the disyllabic nature of the call more than first-winter birds which seem to have a more slurred delivery. This would go some way toward explaining the diversity of call transcriptions for the species.


The Chiffchaff problem

The most likely pitfall in Greenish Warbler identification is provided by certain plumages of Chiffchaff. Within the extensive breeding range of Chiffchaff there exists a number of subspecies. Where these subspecies are not geographically isolated there is continuous gradation of the characters that distinguish them. This makes subspecific identification of all but the most extreme forms very difficult, being based mainly upon the rather subjective appreciation of subtle plumage shades. Observers in Ireland need be concerned with only three of the several recognised subspecies of Chiffchaff. These are: (1) nominate collybita which breeds in western Europe, including Britain and Ireland; (2) abietinus, which breeds further north, from Scandinavia to north and west Russia, down to northern Iran, intergrading with collybita in north Germany and east Poland; (3) tristis which breeds further east, across Siberia and intergrades with abietinus in the west of its range (Williamson 1967).
Personal observations and the observations of several colleagues suggest that Chiffchaffs showing characters of either abietinus or tristis are not very unusual on the Irish coast in late autumn. Bearing in mind that Svensson (1984) advises great caution when attempting to subspecifically identify Chiffchaffs, even birds in the hand, it is probably best to resist placing these birds into a more definite category than "northeastern Chiffchaff" until the problem of distinguishing abietinus and tristis has been thoroughly investigated. On geographical grounds alone it seems likely that the majority of these have a Fenno-Scandinavian origin and are therefore abietinus.
Whereas nominate Chiffchaffs in autumn are typically rather dark with strongly olive-tinged raw-umber brown upperparts and more or less suffused lemon-yellow and olive-buff underparts, typical "northeastern Chiffchaffs" in Ireland in late autumn are noticeably paler and cleaner looking. The following account describes the characters of these birds, they being the Chiffchaff-type most likely to be mistaken for Greenish Warbler.


Pale "northeastern Chiffchaff" in first-winter plumage

Identical in size and structure to P. c. collybitta. Upperparts pale grey-brown with little if any olive, usually confined to the rump. Off-whitish underparts, often faintly washed dull buffish on the throat, breast, flanks and undertail coverts. Supercilium buffish white, brighter and more conspicuous than in P. c. collybitta but, like the latter, the thin pale crescent under the eye tends to be the most striking facial feature at close range; the supercilium is never as long and conspicuous as in Greenish Warbler. Ear coverts washed warm buff. The diffuse breast-side streaking of P. c. collybitta is much reduced or absent. Chiffchaffs of the nominate race can appear to have ill-defined pale wing-bars across the tips of the greater coverts, but in abietinus and tristis Chiffchaffs the wing-bar is often quite striking. It is never so sharply defined as in Greenish Warbler and tends to be longer, involving the tips of all the greater coverts. The prominence of this wing-bar may depend to a large extent on the angle of viewing and light conditions and consequently often has a more transient quality than the true wing bar of Greenish Warbler. Wing-coverts, remiges and retrices dull sepia, edged bright olive green. Alula often noticeably darker than rest of wing.
Bare Parts:
Bill: dark horn brown, sometimes brownish-yellow along the cutting edges, but never conspicuously so.
Legs: usually dark grey-brown to blackish.
Voice: as with Greenish Warbler voice transcriptions vary considerably. The typical call is a plaintive, monosyllabic "pseep" or "weest", the pitch recalling the common "jheet" call of Dunnock Prunella modularis. There is also a more distinctly disyllabic "swee-oo" call (apparently characteristic of "less pale" northeastern Chiffchaff) which has most of the sound concentrated in the longer first syllable.


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Review Findings

By the end of 1970 there were 21 records of birds accepted as Greenish Warblers in Ireland. Single records in 1971 and 1977 which were not accepted were also included in the review as were three recent records between 1981 and 1983. The Panel now considers six of these as acceptable and 20 as unacceptable, including one record withdrawn by the observer well before the review.


Records accepted after Review
  • One, obtained, Great Saltee Island, Co. Wexford, 25th August 1952. (P.W.P. Brown).
  • One, trapped, Great Saltee Island, Co. Wexford, 19th - 28th September 1957. (H. Dick, T. Ennis, F. King, et al).
  • One, trapped, Cape Clear Island, Co. Cork, 25th - 29th September 1964. (R.G. Newell, H.E. Stewart, J.C. Bell, F.Z. Walton, et al).
  • One, Hook Head, Co. Wexford, 12th September 1981. (J.K. Lovatt, M. O'Donnell, et al)
  • One , Hook Head, Co. Wexford, 18th September 1982. (P. Archer, J.E. Fitzharris, K. Grace, K. Mullarney, M. O'Donnell, O. O'Sullivan, P.M. Walsh, et al).
  • One, trapped, Cape Clear Island, Co. Cork, 9th - 15th September 1983. (I. Buxton, J.A. Coveney, J. Torino, K. Preston, et al).
Records not accepted after Review

Unless otherwise stated all records refer to single birds.

  • Cape Clear Island, Co. Cork, 17th - 24th October 1959.
  • Cape Clear Island, Co. Cork, 30th October - 1st November 1959.
  • Cape Clear Island, Co. Cork, 14th October 1961
  • Cape Clear Island, Co. Cork, 8th - 12th October 1962.
  • Cape Clear Island, Co. Cork, 10th - 12th October 1964.
  • Cape Clear Island, Co. Cork, 4th November 1964.
  • Malin Head, Co. Donegal, 18th - 21st October 1965.
  • Cape Clear Island, Co. Cork, 11th October 1967.
  • Cape Clear Island, Co. Cork, 1st October 1968.
  • Cape Clear Island, Co. Cork, 4th October 1968.
  • Cape Clear Island, Co. Cork, 10th - 20th October 1968.
  • Cape Clear Island, Co. Cork, 24th October 1968.
  • Cape Clear Island, Co. Cork, 27th - 28th October 1968.
  • Cape Clear Island, Co. Cork, 5th December 1968.
  • * Two, Lissagriffin, Co. Cork, 29th December 1969.
  • Cape Clear Island, Co. Cork, 4th - 5th October 1969.
  • Cape Clear Island, Co. Cork, 24th - 26th August 1970.
  • Cape Clear Island, Co. Cork, 15th October 1970.
  • Hook Head, Co. Wexford, 11th - 12th October 1971.
  • Cape Clear Island, Co. Cork, 21st - 22nd October 1977.

* record withdrawn by observer before review.

The descriptions of nearly all of these unacceptable records indicate that the birds in question were actually Chiffchaffs. Most of the observers concerned with these records are in full agreement with this view.
Much of what has been published on Greenish Warblers in Ireland in the past must now be considered unreliable. It is therefore appropriate to include here details of the first five accepted records. In the case of the first there was only one observer and a full account is given; the subsequent birds all received the attention of several observers and the summarised accounts are derived from the combined descriptions.


Great Saltee Island, Wexford, 25th August 1952

Thick fog cleared from the island after 09.00 hrs. and I noted a Phylloscopus in the Ash (Fraxinus excelsior) and two Sycamores (Acer pseudoplatanus) near the well about 10.00 hrs. Almost the first thing I saw was the pale wing-bar. The next thing seemed to be to try and trap it, but it would not be driven. So I sat down and watched it and obtained the following description:
About Chiffchaff size. Little yellow in plumage to give pale appearance from front; upperparts dull grey-green, greenest on primaries. Fairly prominent pale supercillary stripe, yellowish behind eye. Noticeable short pale wing-bar, obviously caused by pale tips to major coverts. Underparts whitish-grey, possibly tinged yellow. Tarsi pale brown.
I realised that it was almost certainly a Greenish Warbler and decided that, if I could not trap it, I would try to shoot it with a .22 rifle. I came to this decision because (i) I was alone and could not give confirmatory evidence of my observation. (ii) This is a very 'difficult' species with which I was unfamiliar, and Eversmann's Warbler (Arctic Warbler) may resemble it closely. (iii) I believe that such records as this are of scientific value (this species is spreading its breeding range westwards) and so should be established with accuracy. (iv) This species is numerous in its world population.
So I tried once more to trap it. This time it actually went into the trap and hovered two or three times before the catching box. But it would not enter. At last, because I had no wire door to prevent its escape it flew past me and returned to the same trees. A Chiffchaff was with it there and sometimes they chased each other. Behavior identical. Both had similar notes. The Greenish Warbler's call was a loud "tsweep" rather like a Yellow Wagtail (the Chiffchaff "cheevi"). Several times it sang briefly. The song came quietly with unopened bill, in short (c. 2 secs) hurried phrases - a rather fast warble, quite unfamiliar to me. I jotted down "twissa-wissa-wissa ..." as the start of one such phrase.
Once more I tried to drive the bird but it would not budge. It was pretty clear that it would not enter the trap again anyway. So regretfully I shot it.
Weight at death (probably with some flesh shot away); 6.63 grms. Soft parts: iris dark brown; upper mandible dark grey-brown, lower pale yellow-brown, hue of mauve; tarsus greyish-flesh, toes grey-brown.

P.W.P. Browne

The specimen is preserved in the Natural History Museum, Dublin.


Great Saltee Island, Wexford, 19th-28th September 1957

At approximately 09.35 GMT, an unfamiliar Phylloscopus was noticed in the Observatory garden. The observers were struck by its pale plumage compared to a nearby Chiffchaff and a conspicuous wing-bar on each wing. The bird was successfully driven into the garden trap and captured. The wing formula and wing-bar suggested a Greenish Warbler and the following details were noted in a thorough laboratory description:
Forehead and crown grey-green, nape tinged greener. Long pale yellow supercilium extending from nostril to well behind eye. Dark eyestripe; cheeks pale yellow. Mantle, scapulars, back and rump as crown but tinged greener. Primaries and secondaries dark grey-brown but with bright olive-green outer-web edges forming a noticeable bright panel on the closed wing. The outer six greater coverts on each wing were tipped whitish on the outer webs forming a most conspicuous wing-bar. Feathers much abraded, outer webs washed green, inner webs grey brown. Chin and throat creamy white; breast washed faint lemon yellow, belly to undertail-coverts paler. Irides dark brown; tarsus dark grey-brown. Bill: upper mandible dark horn (blackish); lower mandible yellow-brown. No wing length given but fourth primary longest, third to sixth primaries emarginated. First primary 6mm longer than longest primary covert.
In the field it appeared slightly smaller than Chiffchaff with a conspicuous pale wing-bar. Even in poor light the bright panel across the remiges was easily seen. The lower mandible looked strikingly orange. The only call described was a high-pitched "trree-ep", the r's rolled, uttered when the bird was in the catching box.
The bird was photographed in the hand by T. Ennis.


Cape Clear Island, Co. Cork, 25th-29th September 1964

Watched all day (26th September) in Cotter's Garden in bright sunlight at varying range. The bird was very lively but occasionally paused for short periods.
Field Notes Smaller and slimmer than Willow Warblers/Chiffchaffs with which it was directly compared. Upperparts greyish-green, inclining to greenish-brown when in the shade; underparts very pale greyish-white with faint yellow wash. White tips to greater coverts formed a clearly visible wing-bar. No trace of a second wing-bar. Very prominent pale supercilium, almost meeting on forehead and extending well behind eye. Bill fine, appearing mainly orange/pink. The bird was trapped and the following description taken.
Upperparts: Forehead, crown, nape, mantle, rump and uppertail-coverts all uniform greyish-green.
Side of Head: Supercilium white, washed yellow, extending from base of bill to well behind eye. Skin around eye black with very narrow white crescent below eye. Lores and cheeks white suffused greyish-green, with darker eyestripe behind the eye.
Underparts: Chin to belly white, very slightly washed yellow, strongest on the flanks. Undertail-coverts off-white virtually no yellow wash. Underwing-coverts white, washed yellow on forewing. Tibia pale, dull greenish-yellow.
Wings: Primaries and secondaries dark greyish-brown; all except first and second primaries narrowly edged greenish on outer web. Inner webs of remiges edged whitish. Tertials paler than secondaries and fringed greenish. Primary-coverts dark brown broadly edged greenish; greater coverts same with clearly defined white tips. Wing-bars on both wings symmetrical, made up of tips of outer four greater coverts with a hint of white at the tips of the fifth and sixth. Median and lesser coverts broadly edged greenish.
Tail: Dark grey-brown, all but outer pair of retrices fringed green on the outer web.
Bare Parts:
Bill: upper mandible brownish horn, lower mandible dirty yellow slightly darkening at tip. Gape yellow inclining to orange.
Eye: Very dark brown-grey.
Legs: Tarsus dark grey with narrow yellow line on hind-leg. Soles of feet dull yellow.
Plumage: Apart from one or two primaries which were slightly broken at the tips the remiges and retrices were fresh with no fading at the tips. The body plumage was similarly fresh.
Measurements: Wing: 59.5mm, fourth primary longest. First primary 7mm longer than longest primary covert. Third to sixth primaries emarginated. Weight (on 26th September) 7.35gms.


Hook Head, Co. Wexford, 12th September 1981

This bird attracted the observers' attention by frequently uttering an unfamiliar call, likened to the typical flight-call of Yellow Wagtail.
Size and Structure: Thought to be slightly smaller and marginally shorter-tailed than Chiffchaff but direct comparison with that species not possible.
Head: Crown olive-brown, a shade darker than the mantle; nape paler olive-grey. Conspicuous off-white supercilium widened behind the eye and extended well back to reach nape. Well marked dark eye-stripe, same length as supercilium.
Upperparts: Uniform olive-grey in dull light appearing more olive-green in sunlight.
Underparts: Entirely off-white washed pale yellow on the flanks and undertail-coverts.
Wings: Somewhat browner than mantle with noticeable off-white wing-bar across tips of outer greater coverts, more prominent on one wing than the other. Wing-bar broadest on outer greater coverts narrowing proximally. Wings rather short, like Chiffchaff.
Tail: Browner than rump and uppertail coverts.
Bare Parts: Bill rather fine but in proportion to the head. Upper mandible dark, lower mandible conspicuously light orange-pink. Eyes dark; legs and feet pale brown.
Call: Loud, arresting, high pitched "swee ... sweeoo" or "tswee" vaguely reminiscent of Yellow Wagtail. There was a slight harsh undertone to this note. Occasionally notes were uttered in rapid succession as if the bird was about to burst into song.


Hook Head, 18th September 1982

Discovered in a stand of Willow Salis beside a small pool. An obvious Phylloscopus; size and structure very similar to Chiffchaff but seemed a fraction smaller and slightly shorter tailed. Generally very pale and clean looking.
Head and Upperparts: Uniform pale greyish-green much paler than Chiffchaffs alongside. Conspicuous, long creamy-white supercilium extending from forehead to rear crown. Supercilium widest behind eye then narrowing slightly before ending with a short upward kink at rear extremity. Pale crescent below eye. Ear coverts pale greyish, faintly mottled..
Underparts: Off-white, washed pale yellow at sides of breast and under-tail coverts.
Wings: Generally similar in tone to the upperparts, primary tips browner. Well defined narrow wing-bar on both wings caused by the creamy-white tips to the outermost four to six greater coverts. The wing-bar was rather short and straight, slightly wedge-shaped, narrowing proximally. Although not as conspicuous as the corresponding wing-bar of Goldcrest Regulus regulus it was clearly visible at up to 40m range. Tertials similar in shade to the upperparts with very thin whitish edges and tips to inner webs. Outer webs of tertials, secondaries and primaries edged with yellowish green, obvious at times when the effect was of a brighter panel contrasting with the rest of the upperparts. Primary-projection rather short, about half the length of the exposed tertials.
Tail: Grey-brown, darker than rump, with fairly bright yellowish-green edges to the bases of the outer retrices.
Bare Parts: Bill: similar in size and shape to a Chiffchaff's, lower mandible noticeably bright yellow, becoming horn-brown. Legs and feet: dark grey - not as black as a Chiffchaff's.
Call: Called several times, sometimes in mid-flight and also when being chased by a Chiffchaff; noted as a loud, emphatic "psleeuu" or "psee-oo" reminding observers of the typical flight-call of Yellow Wagtail and a similar note of Pied Wagtail.


It can be seen from the forgoing summaries that all of the birds concerned were remarkably similar and probably all were in first-winter plumage. Observers who have yet to see the genuine article may be pleased to note that after a period of seventeen years without an accepted record, Greenish Warblers have appeared annually since 1981.


Acknowledgements

The Irish Records Panel is most grateful to Dr. J.T.R. Sharrock for his assistance with this review. Lars Svensson and Göran Walinder provided invaluable information on the identification of Greenish Warbler. I thank the staff of the National Museum of Natural History, Dublin especially Liam O'Neill who was always ready to assist and tolerated my occasional intrusions into his working space. Ken Perry and Dick Newell were helpful in providing information relating to certain records and Hugh Brazier went to considerable trouble to obtain published reference material for me. AI am particularly grateful to members of the Irish Records Panel, Peter J. Grant and Clive Hutchinson for providing stimulating discussion and very helpful comments on an early draft of this paper. P.B. Bentz, T. Ennis, Stellan Hedgren, Lars Jonsson, Michael O'Donnell and Julian Torino very kindly provided me with photographs of Greenish Warblers, some of which are published here.


References:

Svensson, L. 1984. Identification Guide to European Passerines. Privately Published, Stockholm.

Valikangas, I. 1951. Die Expansion von Ph. trochiloides viridanus im nordwesteuropäischen Raum, insbesondere nach Finnland, und ihre Ursachen. Ornis Fennica 28: 25-39.

Williamson, K. 1967. Identification for Ringers 2. The Genus Phylloscopus. BTO Field Guide No. 2 Revised edn., Tring.


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