Identification of 2cy Heuglin's Gulls in W Europe - Introduction

Introduction (continued from home page). An important part of the problem is that Heuglin's Gull breeds in remote areas in the tundra. This seriously impedes the setting up of ringing schemes that have helped so much in understanding the moult and migration patterns of its western counterparts. Particularly the extensive colour-ringing schemes for fuscus in Finland (coordinated by Risto Juvaste), intermedius in Norway (Nils Helge Lorentzen) and graellsii the Netherlands (Norman van Swelm, Roland-Jan Buijs) and Britain (Peter Rock) have provided a lot of information. Without any information on origin, it is nearly impossible to study individual birds. True, it is most likely that fuscus and heuglini would occur in Finland and graellsii and intermedius in the Netherlands, but ringed graellsii from Scotland (adult), England (adult) and the Netherlands (3cy and adult) have been observed in Finland and two ringed 2cy fuscus were observed in two consecutive years along a canal in Amsterdam. Thus, it is no longer 100% safe to develop identification criteria based purely on the assumption that, for example, a bird observed in the Netherlands is a graellsii or an intermedius. For this reason, on this web site we use only graellsii, intermedius and fuscus that have been ringed as pulli on respective breeding grounds. For heuglini, the basic data set has been compiled by Visa Rauste in Syktyvkar, Russia. It is extremely unlikely that the western taxa occur at this location. The occurrence of fuscus in Syktyvkar was proven by a ringed bird from Finland. Furthermore, some of the birds photographed by Visa in Russia could represent Steppe L [heuglini] barabensis or Caspian Gull L cachinnans. Some heuglini-like birds showing characters suggesting either fuscus or cachinnans have been excluded from the sample. In principle, this means that we may present only part of the variation found in heuglini. We don't know any well-grounded criteria to separate heuglini and barabensis at this age and therefore the Syktyvkar set may contain an unknown number of barabensis, even if we can assume on geographical grounds that the majority if not all are heuglini.

Presumed 2cy Heuglin's Gull in Finland
© Visa Rauste
Pale 2cy 'lesser-black backed gull' in the Netherlands
© Ruud Altenburg

We also have included some data on heuglini photographed in Finland. These, however, should be considered "presumed Heuglin's Gulls" and are labelled as such; even though it is unlikely, it is impossible to exclude the possibility that some of the Finnish birds are in fact of western origin. Again, ambiguous individuals that could represent fuscus, cachinnans or even Herring Gull L argentatus have been omitted.

When tackling any serious problem, one approach is to subdivide it into several smaller and more manageable parts. For the identification of Heuglin's Gull, we have done this. Even though there are publications on juvenile, 3cy, sub-adult and adult birds, these age classes are extremely similar to graellsii/intermedius Lesser Black-backed Gulls. There is, however, one age class that seems to offer possibilities: those 2cy birds that have returned to Europe from the wintering grounds. After these birds have undergone a complete moult in summer, the taxa again become very difficult to separate; so, the best chance of successfully identifying a 2cy Heuglin's Gull in W Europe is roughly between March and July. This age group and time period is the focus of this web site.

Aim and request. This web site aims to illustrate part of the variation found in 2cy Lesser Black-backed Gulls L f graellsii and L f intermedius, Baltic Gulls L f fuscus and Heuglin's Gulls. To identify a Heuglin's Gull in W Europe, it is necessary to have a clear understanding of the variation shown by local birds. Due to their migratory nature, studying these taxa is complicated and time-consuming; this is especially true if the aim is to document only birds of known age and origin (i.e. ringed birds). This web site has two specific objectives. The first of course is to provide the visitor with an idea of the variation found in these gull taxa, in terms of plumage, moult and structure. Ultimately, we would like to prepare a paper on the identification of heuglini and this brings us to the second objective of the web site, for which we need your help. If you find a ringed 2cy Lesser Black-backed Gull in the period March to July, please take pictures of it. The authors very much welcome all pictures of ringed birds. Please check this overview of all ringed 2cy graellsii and intermedius to see if you can contribute any pictures.

Hopefully with your support we will be able to get a better understanding of the variation in the taxa graellsii and intermedius. This will ultimately help to pinpoint the exact differences between the western taxa and Heuglin's Gull.

Presumed 2cy Heuglin's Gull in Finland
© Visa Rauste
Pale 2cy 'lesser-black backed gull' in the Netherlands
© Mars Muusse

Moult. Much of the discussion of individual birds that we offer is based around comparisons of moult. To understand the significance of the moult pattern shown by an individual heuglini, it is of course necessary to be aware how it differs from that of, say, a graellsii. The order of the accounts presented on this site is intentional: we build up to heuglini by first discussing the plumage and moult of the other taxa. The starting point is graellsii, as this is probably the most familiar bird to most readers. In this context it is worthwhile briefly outlining the moult strategies. Usually 1cy graellsii and intermedius moult few to many scapulars and less frequently also some wing coverts before migrating southward. Subsequently, a limited to rather extensive moult takes place on the wintering grounds, in SW Europe or NW Africa. Besides the forementioned feather tracts, this moult may also include rectrices (tail feathers) and sometimes secondaries. The first complete moult in graellsii/intermedius does not commence until the spring to early summer of their second calendar year. By mid summer, 2cy graellsii/intermedius are therefore in active moult. The moult strategy of fuscus, which winters mainly in E Africa, is very different. Normally, the post-juvenile moult in this taxon is very limited. On the wintering grounds, however, approximately two-third of all fuscus undergo a complete moult. Back in Europe, 2cy fuscus again start moulting, but contrary to graellsii/intermedius, this moult in summer usually is incomplete. The moult strategy of Heuglin's Gull shows overlap with both Lesser Black-backed Gull and Baltic Gull: some birds have only replaced scapulars and therefore match the slowest moulting graellsii, whereas others have undergone a more extensive moult during the winter, often extending to wing coverts, secondaries and tail feathers. A minority (less than 10%) moults primaries too, and a few extremes moult all primaries, and thus are as advanced as the average fuscus. The complete moult of primaries starts on average in early June, approximately one month later than in graellsii.

Acknowledgements. We kindly thank the following persons for pictures and support: Arnoud van den Berg, Andreas Buchheim, Roland-Jan Buijs, Armin Deutsch, Ronald van Dijk, Martin Eggen, Marc Fasol, Alain Fossé, Delfin González, Jan den Hertog, Harm Niessen and Peter Rock.

Further reading. Web sites on the identification Heuglin's Gulls are scarce, so the interested reader probably does best to hunt down some specialist papers. Below is a list of the most useful and interesting ones. It has been annotated, so as to give you an idea about what to expect. If you have suggestions for papers not yet included in the list, please contact Ruud Altenburg.

Bakker, T. 1999. Heuglins Meeuw in Groningen: nieuw voor Nederland? Dutch Birding: 239-240. Short note on the first candidate for the Netherlands [in Dutch].

Eskelin, T. and J. Pursiainen. 1998. The status of 'Lesser Black-backed Gulls' of heuglini, graellsii and intermedius type in Finland. Alula 4: 42-54. First paper on the occurrence and identification of heuglini in Finland.

Gibbins, C.N. 2004. Is it possible to identify Baltic and Heuglin's Gulls? Birding Scotland 7: 154-186. A paper summarizing the current status on the identification of fuscus and heuglini; also adds some new insights. Download.

Rauste, V. 1999. Kennzeichen und Mauser von 'Baltischen Heringsmöwen' Larus [fuscus] fuscus und 'Tundramöwen' L. [fuscus] heuglini. Limicola 13: 105-128 and 153-188. A very comprehensive paper on the identification of fuscus and heuglini, based on birds observed in Finland and Russia [in German].

Stewart P. 2006. The primary moult of the Lesser Black-backed Gull L. fuscus. Special publication No 1, The Severn Estuary Gull Group. Download.

Winters, R. 2006. Moult and plumage variation in immature Lesser Black-backed Gulls in the Netherlands. Dutch Birding: 140-157. Comprehensive paper dealing mostly with variation in Lesser Black-backed Gulls observed in N Netherlands; has an addendum on Heuglin's Gull, plus pictures of some candidates.