West Midland Bird Club

'Variations in Herring Gulls at a Midland Roost'

This article, by a then prominent member of the Club, first appeared in ‘British Birds’ volume 71 (page 338–345), in August 1978. 

Bird and place names were spelt as shown. For their current status, please see our county lists.


The Herring Gulls observed in central England in winter appear to be of at least four distinct types. Can they be related to known races? Where do they originate?

Most species of gull show relatively little individual variation in adult plumage, bare part coloration and size. Lesser Black-backed Larus fuscus and, especially, Herring Gulls L. argentatus do, however, vary quite markedly. This paper is concerned mainly with the diversity observable in the field among adult or near-adult Herring Gulls in England in winter.

I have watched winter gull roosts regularly at Cannock Reservoir[1], Staffordshire/West Midlands, most intensively during the winters of 1974/75 and 1975/76. The Herring Gulls there, which usually number 500 to 1,000, vary considerably, and similar variants occur at other roosts in the West Midland area. Apart, however, from one yellow-legged Herring Gull, I did not notice such frequent differences during regular watching of gulls during 1968-74 in south Wales, where the coastal population is probably essentially local, unlike the purely winter-visiting flocks of central England. Firm conclusions as to the origins and races of these gulls are difficult to draw, but it is worth noting the variety which occurs and relating this to the characters of Herring Gulls elsewhere in Europe. Four main types, A, B, C and D, are broadly separable. These are summarised in table 1 and illustrated in fig. 1 and fig. 2.

Fig. 1. Four types of Herring Gull Larus argentatus observed at Cannock Reservoir, Staffordshire/ West Midlands, during winters of 1974/75 and 1975/76. From left to right: type A (L. a. argenteus?), type B (L. a. argentatus), type C (L. a. argentalus: lauruseri- type variant), type D (yellow-legged type).
See large, black on white, version
(~82 Kb).

type A L. a. argenteus (?)

The majority of the gulls are of this type.

Size Not much larger than Lesser Black-backed Gulls of the British race graellsii.
Bill Pale or rich bright yellow.
Head In winter, dusky, brown-streaked, a small number with whiter heads; increasing numbers develop white head of summer plumage from February (a few from early January: G. H. Green in litt.).
Mantle Consistently pale, between Common L. canus and Black-headed Gulls L. ridibundus in tone.
Wings With rather extensive areas of black.
Legs Pink.

type B L. a. argentatus

From the small, pale type A, there is more or less a gradation to the other extreme. Birds of type B appear at Cannock from early November and may number 100 or more by January.

Size Large or very large, some equalling small Great Black-backed L. marinus.
Bill Long, often very pale or dull
Head Long and angular, dusky with heavy streaks.
Mantle in most, similar to that of Common Gull or a little darker; small proportion look considerably darker still: matt, neutral grey without silvery-bluish tinge of British race, some even approaching palest Lesser Black-backs in certain light.
Wings Broad with reduced black on tips. Largest and darkest individuals in particular with much reduced black on primaries and extra grey extending from base rather than very much more white at tip; and underside of wing-tips may show very little or no black, but subterminal smudge of grey, and apparently complete white trailing edge to tip.
Legs Long, deep pink.

type C 'thayeri' type

These more or less distinct individuals have shown noticeably different wing-tip patterns. Type C gulls, seen irregularly from January to March, numbered no more than about five per winter.

Size Variable, medium-large, from rather large to average type A.
Bill Medium or rather large; dull coloration.
Head Dusky, streaked.
Mantle Darker than in type A (in one case approaching darkest type B).
Wings Tips with much white and little black — precise pattern difficult to see in field and varied in detail, but all individuals appeared to have large white tips to two outermost primaries with subterminal black streak on each (probably restricted to outer web); on next two or three primaries, extensive white areas and sub-terminal black marks; white trailing edge to wing broader than usual on at least one individual
Legs Pinkish.

The wing-tip patterns of this type simulate those described for Glaucous L. hyperboreus × Herring Gull hybrids; at a distance, they could be mistaken for Glaucous or Iceland Gulls L. glaucoides, were it not for their unusually dark upperparts. (During autumn moult, gulls have short or missing outer primaries and much of the black is either absent or, if on part-grown feathers, cannot be seen from above. Black tips are, however, visible on growing feathers part-way along the primaries from below. An apparent lack of black may, therefore, be due to the primary moult rather than a genuine difference in pattern: a more likely source of confusion than the much-discussed effects of wear.)

type D Yellow-legged gulls

This most distinctive form has occurred for at least four winters. In November 1973, an adult Herring Gull with yellow legs was detected by A. R. M. Blake. In 1974, a similar one remained from 2nd November until mid winter, with occasional sightings of other, apparently identical gulls; it was watched by many observers, including J. E. Fortey, E. G. Phillips and D. Smallshire. In 1975, an adult, perhaps the same, was first seen on 1st November, and a series of sightings of both adults and sub-adults followed until February 1976. A near-adult appeared On 30th October 1976 and a full adult in November. All showed similar striking features and were generally quite easy to locate.

Size 'Average' Herring Gull, not especially large.
Bill Not unusually long, but noticeably thick; very bright, deep yellow with large, dark red patch extending slightly onto upper mandible from gonys (also black spot on sub-adults).
Head Large and rounded, on thick, smoothly curved neck. Always appeared pure white on adults all winter (or with only faintest of grey smudging near eye). One sub-adult had small brown marks between eye and bill. Head and bill, together with curved, narrow-based white neck, gave characteristic expression not due solely to white-ness.
Mantle Noticeably dark, slaty grey, darker than Common but not quite so dark as the darkest Herrings. White tips to secondaries always conspicuous.
Wings Long and pointed; prominent white trailing edge, extensive black on tips. Four white spots showed on closed wing-tip; one white mirror on outermost primary (white lacking on sub-adults). Black extended right to base of outermost primaries; very fine, dark shaft streaks on primary coverts. Sub-adults had various amounts of brown on primaries and coverts. From beneath, band of grey across flight feathers almost as dark as on Lesser Black-backed and extensive black patch below tips. Upper wing pattern much more contrasted and clear-cut than on Lesser Black-backed. On arrival (end of October/ early November), all had new and full-grown primaries, whereas other Herrings had outermost short or missing owing to moult (some not full-grown up to six weeks later).
Legs Long; those of adults, bright, rich yellow, regularly noted as being brighter than average winter Lesser Black-backed; those of sub-adults, paler yellow with brighter webs.

In each case, these type D gulls often remained at the reservoir during the day, which few other large gulls did except in fog or hard weather. On most evenings, they fed and rested on or near the shore among groups consisting mostly of immatures, whereas the majority of the adults were in rafts on the reservoir centre.

Type D gulls differed from all other types by their yellow legs, while only a very small number of pink-legged gulls retained such white heads in winter. The yellow-legged gulls had brighter bills than most, especially the dark type B ones: compared with other dark-mantled Herrings, they had brighter bills, whiter heads, much more black both above and below the wing-tips, and darker grey beneath the flight feathers; they moulted earlier; their whole appearance seemed cleaner, neater and more elegant.

Table 1. Different types of Herring Gull Larus argentatus observed at Cannock Reservoir, Staffordshire/ West Midlands, during winters of 1974/75 and 1975/76. See text for full details of types A-D
  Type A
(1,000 individuals)
Type B
(100 individuals)
Type C
(5 individuals)
Type D
(under 5 individuals)
Size Small, short-winged. Slightly larger then Lesser Black-backed L. fuscus. Large, many half to two-thirds more in bulk than small individuals. Medium-large. Medium, long-winged.
Mantle Palest, between Common L. canus and Black-headed Gulls L. ridibundus in tone. Dark, similar to or shade darker than Common (some darker still). Dark or very dark. Dark; slaty grey, darker than Common.
Wing-Tips Fairly extensive black; small white tips and mirrors. Markedly reduced area of black; more grey rather than extra white; broad. Little black, much more white. Extensive black above and below; small white tips and mirrors; long and pointed.
Head in Winter Very dusky, streaked, grey-brown; small proportion whiter. Dusky, heavily streaked; long and angular. Dusky, streaked. Typically pure white; large and rounded.
Bill Pale, to rich bright yellow. Large and long; pale, dull. Medium to large; dull. Stout but not especially long; deep bright yellow with large dark red spot.
Legs Pinkish. Long; deep pink. Pinkish. Long; bright yellow.

Fig. 2. Flight appearance and wing-tip pattern of four types of Herring Gull Larms argentatus observed at Cannock Reservoir, Staffordshire/West Midlands, during winters 1974/75 and 1975/76. From left to right: type A (L. a. argenteus?), type B (L. a. argentatus), type C (L. a. argentatus: thayeri- type variant), type D (yellow-legged type).
See large, black on white, version (~75 Kb).

Discussion

According to the BOU (1971),

Herring Gulls belonging to other races — notably L. a. taimyrensis, L. a. michahellis and perhaps L. a. heuglini — may have occasionally wandered to Britain and Ireland, but we are unaware of any record definitely assignable to any subspecies other than L. a. argentatus.

At present, it seems practically impossible to prove the identity of any race other than argentatus in the field; even with a specimen available it may be difficult. Nevertheless, individuals do occur in Britain which appear to have characters associated with other races; this applies particularly to those with yellow legs, although this character alone is not sufficient proof.

Taxonomy

The taxonomy of the group is notoriously complex, and it is difficult to establish which races are at present acceptable. Some authors still refer to Scandinavian Herring Gulls as L. a. omissus; others regard omissus as no longer valid (a synonym of argentatus), or split it between argentatus and heuglini. Whereas the BOU treats British individuals as belonging to the race argentatus, others consider the Scandinavian argentatus as distinct from British/ North Sea/ Icelandic ones, which thus become L. a. argenteus (the nomenclature tentatively followed in this paper). Some authors have placed the various yellow-legged races as subspecies of the Lesser Black-backed Gull rather than the Herring. Alexander (1954), on the other hand, considered them to be a distinct third species, the Yellow-legged Gull L. eachinnans, characterised by its sleek form, yellow legs, slaty mantle and white head in winter; although he recognised this last feature as a constant character, it has received less attention than leg colour and wing-tip pattern. In Sweden, records of eachinnans and ornissus are no longer generally accepted: yellow-legged individuals are treated merely as variants within argentatus (L. Svensson in litt.). It has been suggested that yellow-legged Herring Gulls in Britain, such as those at Cannock, are also variants.

Barth (1966, 1967a, 1967b, 1968, 1975) undertook very extensive studies of European Herring Gulls, especially in Scandinavia, where he regarded all as argentatus with no subspecific division; the form in the North Sea area, Britain, the Faeroes and Iceland he considered to be argenteus, with diagnostic features of paler mantle, short bill and short wings. In Norway, he demonstrated a continuous cline of L. a. argentatus from south to north (British birds may be regarded as one end of this). The situation is complicated, but, basically, the Scandinavian individuals are palest in the south and darkest in the north and in Finland; British ones are palest of all. Barth gave pale greyish legs as most common in Norway, but yellow or yellowish legs occur throughout the population, with yellow most common in north Norway and Finland (and perhaps most intense in colour in summer). Eye-ring colour varies from yellow through orange to red; orange or red is found widely, but most frequently in the north. It is not, however, associated with the colour of the legs: both pink/ grey-legged birds and yellow-legged ones may have yellow, orange or red eye-rings.

Although there are exceptions, in general the extent of black on the wing-tips diminishes towards the north and northeast. In Norway, a pattern which may be called a 'thayeri- type' (see type C) is found on a small number of gulls, most commonly in the far north. This resembles that of Thayer's Gull L. thayeri (or L. a. thayeri) of North America, with a reduced amount of black, especially on the inner webs, and extensive areas of white on the primary tips. Primary patterns of Scandinavian Herring Gulls as a whole are, however, very variable (Dr P. I. Stanley in litt.)

British Herring Gulls are the smallest: with short bills and wings. All dimensions increase northeastwards, with the largest individuals in Finnmark and Finland. Those in northern Norway are characterised by dark mantles, long bills (except in Finnmark), long wings and tails, and large total size.

Geographical origins

With such extensive variations and the complex taxonomy, it is difficult to suggest with any precision the racial status and geographical origins of all the Herring Gulls observed at Cannock. It does, however, seem clear that those in winter include a very few of the thayeri- type (type C); and others (type B) have exactly those characteristics — large size, dark mantle, little black on the wing-tip — expected of more typical birds from northern Norway or Finland (L. a. argentatus rather than argenteus).

Harris (1971) suggested that British Herring Gulls should have completed their moult by October (earlier than the Scandinavians), and recent British catches have provided further confirmation of this. Herring Gulls roosting inland in southeast England appear to include a low proportion of British individuals, although there is a little evidence that both British and Scandinavian ones winter in Worcestershire (G. H. Green and Dr P. I. Stanley in litt.). The Cannock gulls of type A may, therefore, include some of southern Scandinavian origin rather than be all British: further observations of their state of moult after October should elucidate this. This may in turn support arguments that all should be regarded as argentatus, and that argenteus should not be recognised as a valid race; but, again, the southern North Sea section of argenteus could be involved.

The yellow-legged gulls present most problems. Yellow legs, dark mantle, white head, bright bill and other features which make them distinctive in the field can all be explained in terms of individual variation. One would not, however, expect all these characters — and extensive areas of black on the wings (positively not associated with yellow-legged Scandinavian gulls) — to occur regularly in combination; nor that each individual should moult rather earlier than Scandinavian argentatus. Yellow-legged Herring Gulls trapped in southeast England have in other respects matched type B ones and are therefore likely to have been simple variants as described by Barth (Dr P. I. Stanley in litt.).

Conclusions

Despite the whole spectrum of variations found among argentatus, the constant combination of characters of the Cannock Herring Gulls suggests a distinct subspecies rather than individual variants. It is difficult to establish which one. Of the yellow-legged races, cachinnans has, according to Witherby et al. (1941) [2], extended grey areas (less black) on the outer primaries, with a whitish patch inside the black tip: this does not accord well with the Cannock gulls. The race michahellis of Iberia and the Mediterranean has more black, as does the darkest race, heuglini of Siberia. Both are larger and darker than argenteus and were included by Alexander (1954) in his third species. The race michahellis seems liable to occur in southern England, but a gull visiting central England in winter is perhaps unlikely to have come from the south. The race heuglini seems a more probable winter visitor than either the very similar atlantis of the Azores, Madeira and the Canary Islands or michahellis, but the Cannock Herring Gulls may not be sufficiently large to be ascribed to this sub-species.

Acknowledgements

Lars Svensson helped with references and made comments at an early stage. A. R. Dean, P. J. Grant and E. G. Phillips read drafts and made valuable suggestions and, in later stages, G. H. Green and Dr P. I. Stanley helped to clarify several points. I also thank the observers mentioned in the text for being interested enough to watch and discuss gulls on cold winter evenings beside Midland reservoirs.

Summary

Variations observed among Herring Gulls Larus argentatus wintering in the West Midlands are described and divided into four basic groups according to size, mantle colour, head colour in winter, wing-tip pattern and leg colour. It is suggested that British and Scandinavian birds are involved, with up to 100 showing characteristics — large size, dark mantles and little black on the wings — consistent with a north Scandinavian origin. Up to five per winter have shown characteristics of a 'thayeri- type' variant. Others (fewer than five, and probably the same individuals in successive years) have shown features which suggest a different area of origin — still unknown — and different racial status, being white-headed throughout the year, dark on the mantle, extensively black on the primaries and yellow-legged.

References

R. A. Hume
[postal address removed]

[1^] Cannock Reservoir is know known as Chasewater.

Reproduced by kind permission of British Birds *.

© West Midland Bird Club, 147 World's End Lane, Birmingham, England B32 1JX
Registered charity, number 213311

Ornithology in Staffordshire, Warwickshire, Worcestershire & the West Midlands county, since 1929.

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