Do Mediterranean Shags occur in southwest England? D. S. Flumm

n recent years, there have been several reports from southwest England of Ijuvenile Shags Phalacrocorax aristotelis resembling juveniles of the Mediter­ ranean race desmarestii. This paper summarises the British reports to date and discusses the problems of separating juveniles of the nominate race aristotelis from those of the race desmarestii in the field. As the post-juvenile moult of the Shag commences in September, is arrested during winter, and takes over a year to be completed, the word 'juvenile' is used throughout to describe all Shags up to the autumn of their second calen­ dar-year.

Reported sightings in Britain On 19th February 1986, while looking through a flock of Shags and Great Cormorants P. carbo at the Fal Estuary, Cornwall, I was struck by the appear­ ance of one very distinctive individual (fig. 1). Although clearly a 'Shag-type', it showed gleaming white underparts and large creamy-white upperwing- covert patches. Furthermore, it had a largely yellow bill and bright pink- orange legs and feet. At the time, this combination of characters led me to believe that it was of a different species, so I was somewhat disappointed when an on-the-spot reference to Harrison (1983) failed to confirm this. On 6th August 1985, I had seen a similar bird with an adult Shag flying west off St Ives, Cornwall, and my notebook sketch of that individual also depicts gleaming white underparts and large white upperwing-covert patches. There are two races of Shag in addition to nominate aristotelis: riggenbachi (which is outside the scope of this paper) on the Adantic coast of northwest Africa, and desmarestii (adults of which are similarly not discussed here) in the Mediterranean and the Black Seas. Juveniles of both show gleaming white underparts and pale upperwing patches, as on die two Cornish individuals. There is no clinal variation in Shags, the three races being allopatric. In view of the fact that Mediterranean Shearwaters Puffinus yelkouan are regularly seen in British waters, and die fact that a Shag ringed in Wales was recovered in the Mediterranean, at Valencia, Spain, it seemed not unreasonable that the race desmarestii might possibly occur in Britain. I tentatively submitted

166 \Bril. Birds 86: 166-173, April 1993] Do Mediterranean Shags occur in southwest England? 167 the Fal Estuary rccord to thc British Birds Rarides Gommitteet, and thc following description is summarised from my notebook (scc also fig. 1):

Plurnage as accompanying juvenile Shags, ex- brown as on juvenile nominate aristotelis, bat eept for: white underparts; pale upperwing- most of upperwing-coverts creamy-white. Bill coverts; yellow bill with black eulmen; bright largely yellow. much morc so lhan those of pink-orange legs and feet. Throat, breast and other Shags present, and with dark eulmen belly elear white, bul Hanks washed with grey, ridge and tip. I^egs and feet very difFerent from and grev smudges at sides of lower neck, remi- those of nearby Shags and Great Gormorants, niseenl ofthose of Greal Northern Diver Gavia being conspieuons pink-orange rather than immer in winter plurnage. Forehead, lores, dark brown or black. erown, ear-coverls, nape and mantle dark

At least five observers have beert involved in reporting a total of seven sight- ings ol these striking juvenile Shags in Britain. The reports, each of a singlc individual, are listed below (those which were submitted to the BBRC are marked with an asterisk): Flving west off St Ivcs, Gornwall, on 6th August 1985. St Anthony Head, Fal Kstuary, Gornwall, on 19th February 1986 (fig. 1}.* Hying west olf St Ives on 8th October 1987 (fig. 2).* Mevagissey, Gornwall, on 12th January 1988.* Thurleston. Devon, on 22nd-23rd February 1988.* Flying west off St Ives on 2 ist August 1988. Gwennap Head, Gornwall, on 30th September 1988.*

Not all of those reports submitted to the BBRC were firm claims of desmarestiu and nonc of the five was aeeepted as such.

l'ig. 1. Juvenile (second-calcndar-year! Shag Phalacrocorax aristotdis with plurnage resembling that of Mediterranean rate desmarestii (right), with two typical juveniles (seeond-calendar-year) of nominate race, Fal FiStuary, Gornwall, 19th February 1986 (D. S. Flumm,ßom Flumm 1986)

l'I'he British Birds Rarities Committee is sponsored by Carl £eiss~ r ^A -Oermanj). —1J 168 Do Mediterranean Shags occur in southwest England? Comparison between juveniles of the races aristotelis and desmarestii From 26th April to 3rd May 1991, during a visit to Mallorca, I had thc opportunity to obscrve sevcral juvenile Shags of the race desmarestii. Notebook sketches made at the timc (redrawn as flg. 3) show the similarity between juve• niles of this race and those seen in southwest England and listed above.

Underparts On average, juvenile desmarestii is much palcr (many arc white) on the under• parts than nominatc aristotelis, but there is much Variation in both races (Alström 1985; personal observations). In Mallorca, some juvenile desmarestii had a brownish wash to the underparts while others werc gleaming white. Of the fcw seen standing out of the water, all had dark thighs which contrasted with thc pale underparts (see fig. 3). While this may bc a constant feature on desmarestii, juveniles of thc nominatc race can also be very pale below; indeed, there is onc skin of a nominatc juvenile at the British Museum (Natural His- tory), Tring, which has white underparts and sharply contrasting dark thighs (Peter Lansdown in litt.). Juveniles of the nominatc race have dark thighs, but thc contrast of these with thc underparts is dependent on the degree of pale- ness of the flanks, bclly and vent.

Upperparts Typically, juvenile Shags of the nominate race have the upperwing-coverts much paler than, and thus contrasting with, thc remainder of the upperparts. The degree of paleness is very variable, however, as wearing and bleaching of thc feathers cause these coverts to become progrcssively palcr. Some of the juveniles among the hundreds of Shags which form rafts in autumn in the Isles of Scilly, Gornwall, have cxtremely pale upperwing-covert patches, while

Fig. 2. Juvenile (lirst- or second-calendar-yearj Shag l'hatacrocarax aristotelis with plumage resembling that of Mediterranean race desmarestii (left), wilh typical juvenile (first- or second-calendar-year) of nominate rare, St Ives, Gornwall, 8th October 1987 (D. S. Flumm) Do Mediterranean Shags occur in southwest England? 169 othcrs show barcly any contrast (personal observations). The upperparts pattern of the wcll-markcd individuals closcly matches that of juvenile desmareslii. On average, however, desmareslii has c\'cn palcr, sometimes white, upperwing- covert panels (Cramp & Simmons 1977; Ostrom 1985; personal observations).

Fig. 3. Juvenile (second-calendar-yeari (a-cl and adull (d) Shags Phalacrocorax amlo/dis of Mediterranean raee desmaresäi, Porto Colom. Mallorca, Ist May 1991 (IX S. Flumm) 170 Do Mediterranean Shags occur in southwest England?

34. Juvenile Shag Phalacrocorax aristotelis of race desmarestii, Spain, summer 1985 (Jorge Muntanei)

Ci The inclusion of this photograph in colour has been subsidised by a donation from Carl £eiss—Germany. Do Mediterranean Shags occur in southwest England? 171 Nevertheless, a juvenile Shag with very pale (even white) upperwing-covert patches could still be an individual of the nominate race in worn and bleached plumage; in flight, such individuals look quite different from 'normal' birds (the one that flew west at St Ives on 8th December 1987, fig. 2, was not identified even as a Shag by some of the observers present).

BUI Cramp & Simmons (1977) stated, for juvenile to second-summer Shags of the nominate race, 'Bill pale pink-brown, culmen black' and, for the race desmarestii (no age distinctions given) 'bill usually yellow except black culmen and tip'; while others, for example Alstrom (1985), have described young nominate aristoklis with bills 'dingy yellowish on the lower mandible and along the cutting-edge of the upper mandible, contrasting with blackish culmen'. The Fal Estuary individual's largely yellow bill with black culmen and tip is, therefore, not inconsistent with the bills of some nominate aristoklis. It may be that the intensity of yellow on the bill, at least along the lower mandible, is a feature of juvenile desmarestii. With the exception of the Fal Estuary individual, I have yet to see a juvenile of the nominate race with a bill as bright yellow as those of Mallorcan individuals (fig. 3). My observations in Cornwall have shown young Shags to have grey or pink lower mandibles, with any yellow, if present at all, usually restricted to the base of the mandible.

Legs and feet According to Cramp & Simmons (1977), typical juvenile nominate Shags have 'Foot like adult, but webs and innerside of tarsus pale flesh-brown to yellow- brown.' These darken with age, and the feet of second-summer individuals are described as 'dark brown'. Alstrom (1985) described the legs and feet of adult nominate Shags as 'blackish', while juveniles 'have blackish tarsi with paler, pinkish to brownish-yellowish, inncrsides; the webs and usually, in part, the toes too have die same coloration'. As Cramp & Simmons (1977) described adult desmarestii as having the feet 'brown with yellow webs' and Geroudet (1965) commented that 'their yellow­ ish feet are often quite conspicuous at every age', it would seem that a Shag in at least its third calendar-year with bright yellow feet is likely to be of this race. One of the most striking features of the Fal Estuary individual was its bright pink-orange legs and feet in comparison with ten other juvenile Shags alongside, all of which had dark brown legs and feet. It is, however, evident that there is much greater variation in the leg and foot coloration of nominate aristotelu, particularly juveniles, than is generally realised. On 7th December 1952, at St Ives, N. R. Phillips observed a young Shag witii 'pinky-orange legs and feet' (Birds in Cornwall Ann. Rep. 1952), and in the following year's report the same observer recorded: 'On further check­ ing the leg colour of this species I have found that, in the autumn particularly, considerable numbers of them show a definite tendency to a yellowish hue, this being most noticeable on the webs of the feet . . . juveniles seem to show this more than adults.' Three years later, N. R. Phillips wrote that on 10th September 'a pale bird 172 Do Mediterranean Shags occur in southwest England? at St, Ives had bright, mustard-yellow legs', and, on 28th September, 'at St. Ives, two birds with yellow legs: five with flesh-pink legs, one of which was an adult' (Birds in Cornwall Ann. Rep. 1956).

Structure On average, the race desmarestii is smaller than nominate aristotelis, but, as size differences exist between the sexes, there is sufficient overlap between the races to make this feature of dubious value in the field: for example, an average-sized male desmarestii has the same wing length as an average-sized female of the nominate race (table 1). Table 1. Wing and bill measurements (in mm) of Shags Phalacrocorax aristotelis of the races aristotelis and desmarestii Data from Cramp & Simmons (1977) aristotelis SW England N Scotland desmaresti

Wini; length $ 271 (261-278) 258(243-271) 9 258(251-269) 249 (240-265)

Bill length 6 55.7 (53-58) 58.9 (56-61) 60.9 (58-65) 9 56.2 (55-58) 59.3 (57-63) 63.2 (61-65)

Bill depth 6 10.5(10.2-11} 11.6(10.4-12.1) 10.0(9.7-10.6) 9 9.2 ( 8.3-10.4) 9.9 ( 9.1-12.1) 8.7 (8.2- 9.3) The bill of desmarestii is longer and slimmer than that of the nominate race (Cramp & Simmons 1977) (table 1), and this should be discernible in the field if the two races are observed side by side. Only one of the British sightings listed above mentioned a difference in bill structure, with the individual in question having a bill that appeared longer dian that of other Shags. Table 2. Summary of main differences between juvenile Shags Phalacrocorax aristotelis of the races aristotelis and desmarestii aristotelis desmarestii

Underparts Typically, uniform brown, paler on Typically, white with contrasting dark belly and vent, but some are much thigh patches paler and have contrasting, dark thigh patches Upper-wing- Pale brown to cream panel, fading Whitish, sometimes white, panel, coverts with wear and bleaching, variable distinct on most individuals, but variable Bill Shorter and deeper in SW England Longer and, on average, more slender. populations. Lower mandible pale Lower mandible often bright yellow pink-brown, dingy yellowish, pink or grey Legs Usually blackish on outer sides with Dark brown on outer sides, pinkish to paler pink, brown or yellowish inner brownish-yellow on inner sides; some sides; some are much paler, from are uniformly pale, or with dull yellow mustard-yellow to pinky-orange on front and darker on rear tarsi Feet Blackish, or with webs pale flesh- Brown, with paler yellow webs brown to yellow-brown, darkening with age Wing length Averages longer Averages shorter Do Mediterranean Shags occur in southwest England? 173 Conclusions The main differences between juvenile Shags of the nominate race and juve­ niles of the race desmarestii are summarised in table 2. Given that those of the nominate race can exhibit extreme plumage variation in terms of paleness and pattern of the underparts and paleness of the upperwing-coverts, however, it would be unwise to claim a record of juvenile desmarestii in Britain and Ireland on plumage alone. Nevertheless, a combination of dark thighs contrasting with very white underparts (from throat to vent) and strikingly pale panels on the upperwing-coverts would suggest desmarestii and encourage observers to take a second look. Bare-parts coloration is extremely variable on nominate juveniles, and indi­ viduals with pale (yellow, orange or flesh-coloured) legs and feet do occur. The single most reliable character for separating juveniles of the two races is the bill. This is longer and, on average, slimmer on desmarestii, which also has a brighter yellow lower mandible. This feature, however, should not be used alone, but in combination with underpart, upperwing-covert and leg- and-foot characters.

Acknowledgments I wish to acknowledge the help and advice given by P. G. Lansdown throughout the preparation of this paper, and particularly for his comments and improvements on the first draft and for providing information on the British reports of suspected individuals of the race desmarestii

Summary There have been several reports of unusually pale juvenile Shags Ilmlaoviwax amtolelu resembling the Mediterranean race desmarestii in Cornwall and Devon, and the similarities and differences between juveniles of this race and those of the nominate race are discussed. Juvenile Shags of the nominate race are more variable in plumage and bare-pan colours than is generally realised, and there are currently no grounds for believing that desmarestii has occurred in Britain and Ireland.

References Ai.S'i'RO.M, P. 1985. Artbcstamning av storskarv Phalacrocorax carbo och toppskarv /'/(. arislolelis. Vat Fagebdrld 44: 325-350. CRAMP, S., & SIMMONS, K. E. L. (eds.) 1977. 77K Birds of the Western Pakaretie. vol. 1. Oxford. Fl.UMM, D. S. 1986. Shag in Cornwall showing characters of the Mediterranean race P. a. desmarestii Birds in Cornwall Mm. Rep. 1986. Cornwall Birdwatching & Preservation Society. GfcROUDKT, P. 1965. Water Birds with Webbed Feel. London. HARRISON, P. 1983. Seabirds: an identification guide. Beckenham.

D. S. Flumm, Lyonesse Guest House, Land's End, Semen, Cornwall TR19 7AD