Lovely Larids
by Anthony McGeehan
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Caspian and Yellow-legged Gulls in Donegal In the final decade of the twentieth century two new species of gull were found in Europe. They were not vagrants from distant corners of the planet but two unrecognised forms that had existed under the noses of European birders for thousands of years. It took careful field observations and questioning minds to piece together the sum of their differences from other gulls but once the veil was lifted their distinctiveness could be followed through all plumages that, in turn, led to an appreciation of further unique qualities spanning voice, display and behaviour. What are these new species? One is Caspian Gull Larus cachinnans (known as Pontic Gull in Holland) that hails from the shores of the Black and Caspian Seas with small numbers breeding as far west as Poland.Ê The other is Yellow-legged Gull Larus michahellis from the Mediterranean region and the Atlantic Islands. Yellow-legged Gull was previously regarded as no more than a subspecies of Herring Gull.Ê Now that the genie is well and truly out of the bottle, this classification looks almost laughable - if anything Yellow-legged Gull's nearest relative is Lesser Black-backed Gull, not Herring.Ê Yellow-legged Gulls arrive mainly in southern England (where the species now breeds in small numbers) in late summer following a post-breeding dispersal northwards from the Mediterranean. Large river systems seem to funnel the birds north and, reaching the English Channel coast, some continue inland and spend the winter in Britain. With so few birdwatchers looking for the species in Ireland, yearly occurrence patterns have not yet been properly established. Irish records may also be derived from populations of Yellow-legged Gulls breeding in western Iberia, Morroco and the Atlantic Islands. Over recent springs in Ireland, movements of migrant Lesser Black-backed Gulls have attracted lone Yellow-legged Gulls - presumably some individuals overshoot breeding areas by attaching themselves to flocks of northbound Lesser Black-backed Gulls. Nowadays, interested and well-informed birders in Britain and north-west Europe have learned to recognize both species - in keeping with a growing awareness of their identification criteria. For example, Caspian Gulls are found in small numbers each winter in eastern and central England (mainly inland as the species is primarily a "freshwater" gull. The frustration that attaches to this exciting turn of events is twofold.Ê On the one hand, it is not possible to pick up a field guide and study clear illustrations of either species.Ê Instead, you have to access identification papers in those magazines that carried the original trail-blazing articles.Ê The most important of these were by Detlef Gruber in 1995 (Limicola 9:121-165), Ronald Klein and Detlef Gruber in 1997 (Limicola 11:49-75), Martin Garner and David Quinn in 1997 (British Birds 90:25-62, 369-383), Lars Jonsson in 1998 (Alula 3:74-100) and Theo Bakker, Rudy Offereins and Rik Winters in 2000 (Birding World 13:60-74). The new gull guide by Klaus Malling Olsen (due in spring 2002) should fill a gap in the reference book market and, if you really want to keep abreast of field identification and see lots of individuals, the best way to learn is to visit one of many excellent gull sites on the internet.Ê On the other hand - and from a peculiarly British and Irish perspective - the acceptance of Caspian and Yellow-legged Gulls as valid species has not yet been officially embraced by so-called taxonomic authorities in Britain and Ireland. It seems that, for birdwatchers here, Lars Jonsson wrote in vain when, in his major article on the identification of Caspian and Yellow-legged Gulls in Alula in 1998 (see above) he commented: "The birding community must be prepared to treat cachinnans and michahellis as representing taxonomic species." Ê The purpose of this article is to place on record details of occurrences of both species in, of all places, Donegal.Ê Ireland's first Caspian Gull was recorded at Belfast (on the city's main rubbish dump) on 13th February 1998.Ê It was a third-winter and was seen by AMG and Richard Millington.Ê The record was passed by the Northern Ireland Birdwatchersâ Association to Lars Jonsson who accepted it.Ê The next Caspian Gull to be discovered was in the Irish Republic - a third-winter found at Killybegs by RM and Mark Golley on 13-14th March 1998.Ê RM managed to film this bird and a jpeg still image is reproduced here.Ê
Click here for a larger image On 12th February 1999 AMG found a full adult on the foreshore at Derry rubbish dump.Ê The border with the Irish Republic is marked by a small stream which flows across the mudflats a mere 200meters north of the rubbish dump, so this Caspian Gull was often standing on the Donegal shoreline of Lough Foyle - constituting the second record of the species for both Northern Ireland and the Republic of Ireland.Ê A return visit on 15th February resulted in the bird being seen again.Ê A small band of birdwatchers enjoyed good views of it and, even though it was new to all of them, everyone was impressed with how distinctive the gull was.Ê Photographs were taken - unfortunately at long range.Ê Two are reproduced here.Ê
Click here for a larger image Detailed field notes were compiled on both days and read as follows: "Caspian Gull, Derry dump, 12th February 1999. The bird was an immaculate adult with a pure white head.Ê Its bill colour was different from the many Herring Gulls around it.Ê Their bills were bright, rich 'Kodak' yellow with a clear red gonys spot.Ê The Caspian Gull had a paler yellow bill, which was slightly tinged greenish.Ê The colour was not unlike that of a Common Gull's bill.Ê The tip of the bill was paler and perhaps a purer yellow.Ê A dark smudge extended up from the gonys onto the side of the upper mandible.Ê The pale tip joined the greenish-tinged yellow base above the dark smudge on the gonys.Ê Better views on 15th February revealed that there was actually some red around the gonydeal angle and above this the black began.Ê The bill was, in proportion to that of a Herring Gull, both longer and more parallel-sided. Unlike Herring Gull, there was no obvious thickening around the gonys and no sharply inclined downturn to a hook-like tip.Ê Running back into the bird's face, there was a long gape line.Ê This came across as a strong difference in facial character from Herring Gull.Ê The gape line was exaggerated by a line of shadow running along the cutting edge of the bill. This linked with the gape line and made the latter seem more continuous and therefore eyecatching.Ê Ê The head shape was distinctive.Ê At times it was pear-shaped with an 'Eider' profile running forwards and downwards from a rounded (egg-head) peak just above the eye.Ê Occasionally it appeared big-headed with a proud, uplifted chest and - at times - a peculiarly bulbous nape.Ê Emphasising the somewhat front-heavy shape, the bird's rear was noticeably slim behind the legs and very neatly proportioned.Ê The eye was always outstanding: a pin-hole of black on the head.Ê Even though, at this range, the Herring Gulls did not look noticeably pale-eyed, the Caspian Gull showed an even smaller, blacker eye.Ê The Herring Gulls' heads also had a furrowed crease in which the eye sat.Ê The Caspian Gull didn't, which gave rise to a quite unique expression: that of a smooth snow-white head punctured by a tiny black beady eye.Ê Contributing to a different look was the eye's position - further forwards and slightly higher on the side of the head than on Herring Gull.Ê The proud chest served as a kind of prop for the bill and the bulge in the chest extendedÊ (like a kind of anvil or large bosom) as far forwards and outwards as the gonys. ÊThe upperparts were slightly darker than an argenteus Herring Gull.Ê The colour was clean and 'pure' and closer to that of a Common Gull (actually a fraction darker) but a brighter (freshly painted) grey.Ê It was easy to notice the bird's different upperpart shade and to use this to pick it out from among lighter-backed Herring Gulls.Ê In dull light the colour difference was at its most marked; in sunlight the different tone was not so obvious.Ê At no closer than 100meters all that could be distinguished on the folded primaries were four small white tips.Ê These were smaller and more 'isolated' than on a Herring Gull.Ê There was more white visible at the very tip of the wing - at the overlap of primaries 10 and 9 on the upper side of the folded (near) wing.Ê All of the bird's back, from the edge of the scapulars to the folded primaries, was flat in outline and didn't show an obvious tertial step or much feather bulk. The legs were clearly longer than a Herring Gullâs, both above and below the knee.Ê The longer leg length was particularly striking when the bird was standing alongside Herring Gulls in water: there was much more 'daylight' between its body and water level (see photograph). The leg colour was not easy to discern.Ê The legs might have been pinkish or yellowish. ÊTheir main tone was pale - paler than a Herring Gull.Ê The feet were definitely tinged peachy-yellow (easy to see when the bird preened) whereas the upper leg (tibia) had a greyish hue.Ê The legs were also thinner and 'straighter' than a Herring Gull's and, in combination with their length, suggested the shape of a pair of chopsticks.Ê Consequently, the Caspian Gull stood taller than a Herring Gull (and it was also very slightly bigger in body size).Ê When walking the Caspian Gull had a more waddling gait and the longer legs were picked more deliberately off the ground. Ê When giving its 'long call' at rest, the bird jabbed its bill directly skywards, at 90 degrees, and adopted this position with a rapid movement.Ê In their analogous calling posture, it was obvious that Herring Gulls did not throw the head back quite so far and instead held it at only 45 degrees.ÊÊ At other times the Caspian Gull stood very tall and upright and looked remarkably long-necked, like a giraffe.Ê Especially during these moments it strongly reminded me of a Slender-billed Gull (long neck, long lores and a pear-shaped head). Ê Views were more than adequate to see the diagnostic pattern to the underside of primary 10.Ê During preening the wings were drooped and the underside of the far wing showed a long white tip to P10, within which there was a tiny black mark (symmetrical, and near the edge of each side of the feather).Ê At the point where the underside of P10 was aligned against the tail tip, the white on the underside of the feather was replaced by black.Ê The black area took the form of a rectangle before giving way to pure white even further back along the featherâs broad inner web.Hence, with the exception of the tiny black mark among the white tip, the pattern was of a white tip, black band and white base.Ê This pattern is diagnostic and was easy to see.Ê In flight the rest of the underwing was a clean, bright white.Ê There was little by way of a grey 'show-through' along the remiges.Ê
Click here for a larger image and a detailed caption The upperwing was seen well several times, especially when the bird spreadeagled its wings shortly after landing.Ê The long white tip to P10 was complemented by a large white mirror on P9 that, together, formed a white roundel surrounded by black spanning the rest of the wing tip. Ê On the spread wing it was possible to see pale, greyish-white tongues intruding into the black region across the 'hand'.Ê These took the form of pale slots and ran like fingers into the inner webs of several outer primaries.Ê This feature was checked for specifically - otherwise its significance would hardly have been detected.Ê Another fine point (although with less diagnostic importance in terms of identification) was to ascertain the precise pattern on P5.Ê Once again, this was seen clearly by concentrating on the exact feather during wing-stretching.Ê The pattern consisted of a clear-cut black bar.Ê On 15th February 1999 the Caspian Gull began to make regular sorties over the mudflats and seemed to be looking for razor-shells.Ê During these flights it used a long, graceful 'slow motion' take-off.Ê It dangled its legs and trundled into flight with a long, Albatross-like taxi.Ê Still dangling the legs, it periodically swooped gracefully over the mud surface to pick up shells.Ê At these times it resembled a huge Black-headed Gull in its manner of flight.Ê Once, having found a food item, it was robbed by a Herring Gull.Ê The Caspian Gull didn't fight back and seemed somewhat timid. Often, even when walking randomly on the mudflats, the Caspian Gull had a habit of lifting its wings and even keeping them 'half aloft' while it moved around." Yellow-legged
Gull On 21st January a first-winter was discovered in Killybegs by AMG, Richard Millington and Mark Golley and was filmed by RM.Ê Descriptions and images of the last two individuals are presented below.
Click here for a larger image "Yellow-legged Gull, second-winter moulting into second-summer (third calendar-year) plumage at Glencolmcille on 28th May 2001. A check through about one hundred Herring and Lesser Black-backed Gulls on the estuary at Glencolmcille turned up a dark-backed sub-adult gull with clear yellow legs.Ê The bird's identification as a Yellow-legged Gull was straightforward and consisted of the following key points. The legs were obviously yellow but were not especially bright in colour (probably related to the age of the bird).Ê The legs were longer than those of a Herring Gull, noticeably so above the knee.Ê They were not thin like the legs of Caspian Gull.Ê Standing among other gulls, the Yellow-legged Gull stood taller and looked more stately, haughty and regal.Ê Standing in long grass the bird seemed to have 'an extra inch' between its body and ground level. The upperparts were darker and also a smart blue-grey shade compared to the paler pearly-grey of Herring Gull.Ê Although the mantle and scapulars were essentially an adult-like blue-grey, the wing coverts and tertials contained two generations of feathers: with new blue-grey feathers emerging among older brown immature ones.Ê The blackish-based, whitish-fringed tertials (typical of a second-winter Yellow-legged Gull) were a prominent feature even though they were now worn and at least one had been replaced by an adult-like tertialÊ (with others actively growing).Ê More covert replacement had occurred among the median coverts than elsewhere on the wing.Ê In flight this set off a variegated pattern with most blue-grey colour concentrated as a mid-wing band across the median upperwing coverts. The bird's head and bill shape were fantastic. The bill was about 10 or 20 per cent deeper across the base than in a wide selection of Herring Gulls sampled. The bill was bright yellow (without the more yellow-orange flush shown by the breeding plumage Herrings) with a vermilion-red spot on the gonys and a black band across both mandibles including all the tip of the lower mandible.Ê The absolute tip of the upper mandible was a pale, watery horn-yellow (almost whitish). In shape the bill was stout, heavy and fat-based.Ê It was very straight along the culmen.Ê The downturn to the tip was more abrupt and with a steeper angle than in a Herring.Ê This, of course, is the classic adult Yellow-legged Gull bill shape - like a bread knife.Ê There was an obvious gonydeal angle but even this was flatter than in Herring Gull. At times the bulk and shape of the bill reminded me of a short-billed Glaucous Gull.Ê In contrast, the bills of the Herring Gulls were dinky, shorter and ö especially ö more decurved.Ê Their bills had a hint of a banana shape that seemed to start from the origin of a line through the eye, lores and bill base. The nostril was better defined than in Herring Gull - there was a heavier shadow in this area of the bill.Ê Where the bill 'plunged' into the face there was a kind of fat jowl (and vivid orange inside the mouth). The head was noticeably big and heavy.Ê Most arresting was its flat top - as though 'ironed'.Ê Hence the profile was of a flat bill culmen, steep forehead and long, flat top to the head.Ê There was no asymmetric head profile as in Herring Gull (with a rounded head shape rising to a slight peak at the rear of the crown).Ê The eye was definitely a little bigger than a Herring Gull's and more elliptical, with the ellipse set in a horizontal plane.Ê The pupil was proportionately bigger and darker than a Herring Gull and the iris was thinner and paler yellow.Ê By comparison, Herring Gull eyes looked smaller and more beady with a 'Jackdaw' expression.Ê The orbital ring was deep, bright red (the orbital rings on the Herring Gulls were orange).Ê This was easy to see and the Yellow-legged Gull had by far the most conspicuous orbital ring of any large gull in a group of around a hundred gulls.Ê There was quite a pronounced shadow above the eye: giving it more of a mean, furrowed brow than a Herring Gull.Ê The primaries were a plain blackish brown and were well worn. The primary projection was noticeably long - longer and more attenuated than any of the Herring Gulls.Ê In flight there was a vivid contrast of a blackish tail band against gleaming white upper-tail coverts.Ê The overall pattern in flight was reminiscent of a first-winter Common Gull - but much brighter with richer colours and more crisp contrasts.Ê The underwings were extensively patterned with dark brown mottling across all the feather tracts.Ê The gull looked long-winged when it flew off inlandÊ (my last view of it)." Arguably more interesting than the Glencolmcille discovery of a Yellow-legged Gull in an 'easy-to-identify' adult or adult-like plumage, was noticing a young individual.Ê Fortunately all three of us who had the great luck to encounter a first-winter tucked away among numbers of young Herring Gulls on rooftops in Killybegs on 21st January 2002 had previous experience of this age of Yellow-legged Gull at this season. Ê
Click here for a larger image The first impression was of a similarity to a young Great Black-backed Gull.Ê This was due to a fairly contrasty, monochrome colour scheme.Ê However, the bird's size and structure indicated that it was something else.Ê The shape and proportions were distinctive: a stocky body similar in size to a Herring Gull but with a more thickset build (bull neck especially) recalling a Mediterranean Gull.Ê The 'muscular' foreparts give way to a much more elegant rear with the long primary projection more than compensating for the bulky head, neck and chest. To the practiced eye, the legs on Yellow-legged Gull are a useful field character.Ê They are longer than in Herring Gull but also relatively thick.Ê Even the feet (if they can be seen) look big.Ê Standing on the rooftop, it was possible to see the bird's feet well: they were a bit more fleshy and 'duck like' than those of the Herring Gulls nearby.Ê The bill was a key feature.Ê Young gulls do not have a fully-grown bill until they are at least a year old.Ê Think of the difference this produces in the bill shape of a first-winter Mediterranean Gull in comparison to an adult and you will grasp the structural significance that can be noticeable in the field.Ê The same often applies to young Yellow-legged Gulls, which have a less sharply contoured bill than an adult (see above description and photograph of a third-summer at Glencolmcille for a typical adult bill shape).Ê The good news is that even a first-winter Yellow-legged Gull has a characteristic bill shape (and indeed colour). Think of a first-winter Razorbill's bill and you have got a near-perfect analogy. Richard Millington's most instructive jpeg portrays all of the bird's plumage details well.Ê In particular, note the following significant features. The scapulars are second generation feathers.Ê In other words, the bird has completely moulted its juvenile scapulars.Ê There is nothing unusual in this - most first-winter argenteus Herring Gulls have a similar moult of their scapulars - but young Yellow-legged Gulls start this process much earlier in the year, due mainly to a much earlier breeding season.Ê The point here is that the scapulars on the Killybegs bird were not only of a second generationÊ - they were also more worn than those of the Herring Gulls, the excess wear being a result of their older age.Ê In fact, if you look at a selection of argenteus Herring Gulls in late winter (say, between January and March) you will see that some will still be renewing the very last one or two rows of their lower scapulars (the last brownish juvenile scapulars remain at the boundary of the lower scapulars and greater wing-coverts).Ê All of the second generation (first-winter) scapulars are newer and relatively unworn - a far cry from the condition of the Yellow-legged Gull's scapular feathers.Ê Incidentally, in argenteus Herring Gulls, as the process of scapular replacement advances lower down the back, many birds produce a scapular pattern that is less boldly marked: lacking a clear broad subterminal 'cross-bar' or a rounded 'ace-of-spades' internal pattern.Ê Instead, there is a smoky-grey wash across these late-growing feathers (which corresponds to a closer similarity to a second-winter feather, while still actually being a 'first-winter' feather). Of major significance was the fact that, not only were the scapulars of a second generation, but some of the wing coverts were too.Ê This is very different from first-winter Herring Gulls (or Great Black-backed Gulls) that do not begin to replace juvenile wing coverts until the commencement of their springtime head and body moult.Ê Careful scrutiny of the photograph reveals a mixture of juvenile and first-winter wing coverts (look, in particular, at the first-winter inner median and lesser coverts) Click here to view the first-winter photo again. The net effect is to produce a more homogeneous pattern, linking the scapulars in appearance with the new (second generation) wing coverts. The tertials differed between the bird's left and right sides.Ê While they were extremely worn on both sidesÊ (again typical of a first-winter Yellow-legged Gull at this time of the winter) the two old lowermost tertials on the right-hand-side showed whitish tips.Ê Apart from this, the overall colour of the tertials was blackish or blackish-brown. The region around the birdâs ear-coverts is finely streaked and almost takes on the form of a mask.Ê This is again somewhat reminiscent of a first-winter Mediterranean Gull and is also a common 'look' for a first-winter Yellow-legged Gull.Ê The convex shape to the forehead is also typical. Although hard to see clearly on the picture, the tail, upper-tail coverts and undertail can be viewed to a limited extent - but sufficiently well to see their diagnostic patterns.Ê The tail showed an inky black band on a snow-white ground colour.Ê In flight the black tail band was 'framed' in white: albeit narrowly along the tail tip.Ê The narrow white tail tip is discernible in the photograph.Ê The tail was slightly damaged along the tips of the central tail feathers (also visible in the photo).Ê The uppertail coverts were flecked with black in a random scatter - there was no regular concentric arrangement in the pattern and the upper-tail was basically white.Ê Compared to Herring Gulls of equivalent age, the Yellow-legged Gull had very clean, whitish undertail coverts that were almost unmarked. In flight, as well as having a clear white rump and upper-tail coverts, the bird had virtually no pale window across the inner primaries. Acknowledgements
Anthony
McGeehan |
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