Heuglin's Gull (L. heuglini / antelius)

(last update: 6-3-2011)

adult heuglini: March

Is it possible to identify Baltic and Heuglin's Gulls?

By Chris Gibbins, IN: Birding Scotland 7(4), December 2004.

Abstract

In 1998 Lars Jonsson wrote a groundbreaking paper on the identification of Baltic Gull Larus fuscus fuscus. The paper was important because it presented new identification criteria for the separation of fuscus from graellsii and intermedius Lesser Black-backed Gulls. Around the same time, Visa Rauste produced a similarly important paper dealing with the separation
of Baltic Gull from Heuglin's Gull L. (f.) heuglini (Rauste, 1999). A novel and significant aspect of these papers was that they used moult to help support identification. Other notable contributions to the identification of these gulls were made by Eskelin and Pursiainen (1998) and Gruber (1999).
Here I provide an update on the identification debate surrounding fuscus and heuglini. The paper is based on field studies of these taxa in Europe and the Middle-East and includes a review of recent ideas that have developed from research being undertaken by other gull enthusiasts, much of which is not yet formally published. The principal aim is to review
progress made since the work published in the late 1990s.

Introduction: a history of views on the taxonomy and identification of fuscus and heuglini

Baltic Gull Larus fuscus fuscus (hereafter fuscus) is the nominate form of Lesser Black-backed Gull. It was once thought to be regular visitor to the UK. For example, Buckland et al. (1990) listed 17 fuscus records in North-East Scotland between 1975 and 1984, including a pair frequenting a rooftop breeding colony in Aberdeen throughout the summer of 1982. At this time, any small, black or blackish-backed bird with only one primary mirror was considered to be a fuscus. However, Jonsson (1998a) demonstrated that both the plumage and structure of fuscus overlap with intermedius Lesser Black-backed Gull, a form that occurs regularly in the UK. Thus, Jonsson's paper suddenly cast doubt on the identification and status of fuscus in the UK. Buckingham (1998) also questioned the credibility of many British fuscus records,
suggesting that descriptions point strongly to birds having been intermedius.

Jonsson's paper was significant because it also presented new criteria for the identification of adult and immature fuscus. Effectively it marked a reset point, with previous records shelved and a requirement to identify future candidates using strict new criteria, including moult. At the present time this strictness is important because fuscus has suffered marked declines across its breeding range (Most recently this trend has been halted. Surveys in summer 2003 suggested that the Finnish population has remained stable over the last few years at around 8400 pairs (BirdLife Finland, 2004).) and so is likely to be a much less frequent visitor to the UK than perhaps it once was. Based on Jonsson's criteria, candidate fuscus have been seen in several countries bordering the North Sea, including birds photographed in the Netherlands (site Ruud) and Cambridgeshire (Birding World 17 (5), p. 180).
Most recently, a ringed fuscus (ring code CXVA) was seen at Westkapelle in the Netherlands on 16th October 2004.

Because of differences in plumage and particularly its moult and migration strategies, the Dutch committee for avian systematics (CSNA) accorded fuscus species status (Sangster et. al., 1998). However, more recent studies have demonstrated that there is significant gene flow between fuscus, graellsii and intermedius (Liebers and Helbig, 2002; Liebers et
al., 2004). Consequently, the rather hasty CSNA decision to split fuscus has now been reversed (Sangster et al., 2003).

Heuglin's Gull L. (fuscus) heuglini is something of an enigma. It breeds in Arctic Russia, typically in rather low densities in open tundra habitat with bogs and marine islands. The most westerly known breeding areas are around the White Sea, although the possibility exists that birds may be breeding in Finland (see Summary and Discussion section). Few European ornithologists have experience of heuglini on its breeding grounds and it is clear that considerable uncertainty exists among UK birders concerning its identification, nomenclature and
taxonomy. It is often called Siberian Gull, although to help avoid confusion with other Siberian taxa, Buzun (2002) suggested that the name West Siberian Gull should be adopted. It is also sometimes called Tundra Gull (e.g. Luoto et al., 2002), reflecting habitat use on the breeding grounds. Traditionally it has been seen as comprising two forms: heuglini in the western part of its range and taimyrensis in the east. Genetic studies have shown that Heuglin's Gull is very closely related to the Lesser Black-backed Gull taxa (Liebers et al., 2001; Liebers and Helbig, 2002; Liebers et al., 2004). At the moment it is not entirely clear whether it should be classified as yet another subspecies of Lesser Black-backed Gull (i.e. as L.f. heuglini) or accorded species status (i.e. L. heuglini). While genetically it is more worthy of species status than fuscus, Liebers and Helbig (2002) argue that it is very much a borderline case and, for the moment, is perhaps best treated as a form of Lesser Black-backed Gull. Conversely, Yèsou (2002) suggests it should be treated as a full species. Heuglini is treated as a full species in the recent Helm gulls monograph (Malling Olsen and Larsson, 2003).

In his rather confusing paper, Buzun (2002) argued that the type specimen of Heuglin's Gull (i.e. the nominate L. h. heuglini) is in fact a taimyrensis. By convention, this means that the taimyrensis population should become the nominate form of what Buzun called West Siberian Gull (i.e. L. h. taimyrensis becomes L. h. heuglini). The western birds would
therefore need a new subspecific name, for which Buzun suggested L. h. antelius. However, Yèsou (2002) put forward a number of persuasive arguments as to why taimyrensis as a form has no taxonomic validity (this is discussed in detail later). If Yèsou's arguments are correct, Buzun's re-identification and re-naming are irrelevant, as Heuglin's Gull simply comprises one form – heuglini from west of the Taimyr Peninsula.

The taxonomy of heuglini certainly seems complicated and confused, but what about its
identification? On geographic grounds, anyone encountering birds with mid to dark grey upperparts in the Middle-East (birds paler than the fuscus but slightly darker than the barabensis that also winter in the region) can be reasonably confident with their identification as heuglini. However, the upperpart tone of heuglini overlaps with graellsii and
intermedius (Figure 1). The separation of heuglini from graellsii and intermedius may initially seem an irrelevant problem for birders looking at gulls in Scotland, but birds thought to be heuglini are now being recorded regularly and in good numbers in Finland, further west than it was once thought to occur.

The status of heuglini in Finland and the fact that it is a long distance migrant suggest that
this taxon is a potential vagrant the UK. Indeed it is not inconceivable that, like Caspian Gull
L. cachinnans, it has been overlooked in the past and actually occurs regularly in the UK.
Thus, it is important to be aware of how a heuglini might look standing within a group of
graellsii or intermedius. Much of the early identification literature on heuglini now appears
somewhat dated in its approach or is hidden away in rather obscure (often Russian)
journals that are not really accessible to UK birders. In many cases this literature concentrates
on biometrics and so is not particularly useful for field identification. Harris et al.
(1996) covered the identification of heuglini in their book on European and Middle-Eastern
birds, one of the first field guides to do so. However, the treatment of heuglini in this book
is rather simplistic, with many statements not supported by subsequent studies. More
recently, papers dealing with the field identification of heuglini and its status in Finland
have been published in Limicola (Rauste, 1999) and Alula (Eskelin and Pursiainen, 1998).
Visa Rauste's work is extremely detailed and compares both the plumage and moult of
heuglini with fuscus. Unfortunately, only the summary and plate captions of this paper are
in English. Garner (1997) and Kennerley et al. (1995) discussed the identification of
heuglini on the wintering grounds.

END OF PART 1

CONTINUE AT PART 2