It’s all very well to have distinct, artificial categories like Caspian – Steppe – Heuglin’s Gull, but what if you keep seeing gulls that do not fit into any of these “boxes”?
Caution! This is a long and tedious read about Asian gulls!
[Note: You can click on pictures for bigger version.]
In January 2014, Chris Gibbins and I visited the Black Sea coast in Georgia, with the idea of studying Russian Common Gulls (Larus canus heinei) in the field. This research trip was sponsored by the Dutch Birding fund. There were thousands of large gulls, especially in the Chorokhi delta south of Batumi, and in Poti, a rather industrial coastal city with a big harbour. The vast majority were Caspian Gulls, but we also saw quite a few Yellow-legged Gulls (Larus michahellis), about a hundred Armenian Gulls (Larus armenicus), 15 Herring Gulls (Larus argentatus – a vagrant in Georgia), 4 Baltic Gulls (Larus fuscus fuscus), 2 Pallas’s Gulls (Larus ichthyaetus), and tens of Heuglin’s Gulls (Larus [fuscus] heuglini).
A few Caspian Gulls on the beach at Poti…
From day one it became clear that among these thousands of gulls there were some odd adult birds, looking a bit like Heuglin’s Gull but with paler upperparts and somewhat less black in the wingtips. Were we perhaps looking at Steppe Gulls (Larus [cachinnans/fuscus/heuglini] barabensis), a taxon that winters in the Persian Gulf and India and that has not been recorded in Georgia before? These birds were trouble. It is nice to have books and papers that classify gulls into distinct categories like Caspian – Steppe – Heuglin’s Gull, but what to do when it is obvious that the gulls have not read any of this and do not care for such categories?
Allow me a quick recap. What exactly is a Heuglin’s Gull, what is a Steppe Gull, and what do they look like? Adult Heuglin’s Gull has been described by Rauste (1999) and Buzun (2002). Most authors seem to consider it a subspecies of Lesser Black-backed Gull, as it is very similar in plumage and there is evidence of some gene flow between fuscus and heuglini. However, the long calls of Heuglin’s Gull are slightly different from those of Lesser Black-backed, and some authorities advocate full species status. Essentially, adult Heuglin’s Gull looks very similar to adult graellsii Lesser Black-backed Gull, though some birds have slightly paler upperparts. The black wingtips are very extensive, with only a short pale tongue on underside of outermost primary (usually covering about 1/3 of the inner web, but sometimes up to ½). The tongue mainly has a diagonal shape, not concave or rectangular. From above, the black colour on the outermost three primaries (P8-10) reaches the primary coverts, creating a solid black outer hand. Most birds (95%) show black down to P4. The white mirrors are small; the one on outermost primary (P10) nearly always shows a complete distal black band, and the one on P9 never breaks the black outer edge of the feather. Nearly all birds show head streaking in winter (until March) and their leg colour is variably dull yellowish to greyish/pinkish – rarely bright yellow.
A typical (though rather dark) adult Heuglin’s Gull together with Caspian, Armenian and Black-headed Gulls, Poti. Compare mantle colour to that of the Armenian Gull immediately behind.
The same Heuglin’s Gull in flight. Black colour on P8-10 reaches the primary coverts. On the underside of P10, there is only a short, diagonal pale tongue (indicated by the black arrow).
Steppe Gull is a poorly differentiated taxon and is clearly very closely related to Heuglin’s Gull. The two taxa are genetically very similar. However, not all of its long calls are similar to those of Heuglin’s. Steppe Gull is said to have two different types of long call, one being much closer to Caspian Gull. Nowadays, most authorities seem to consider it a subspecies of Heuglin’s Gull (or a subspecies of Lesser Black-backed Gull, if you consider Heuglin’s to be part of Lesser Black-backed Gull too), but it has also been grouped with Caspian Gull or even been treated as a full species. In any case, it is believed to have a hybrid origin. To make things even more complicated, mixed colonies of Caspian and Steppe Gulls have been reported from southern Siberia, and birds breeding in northern Kazakhstan appear to show characters intermediate between these two taxa.
The characters of adult Steppe Gull have been described by Panov & Monzikov (2000). Photographs from the breeding range can be seen at http://birds-altay.ru/chajka-larus-barabensis/, and from the core wintering range at, e.g., http://chrisgibbins-gullsbirds.blogspot.de/2010/05/steppe-gulls-in-uae.html. Its upperparts are dark bluish-grey, similar to Armenian Gull (Larus armenicus), and the black wingtips are slightly less extensive than in Heuglin’s Gull. The pale tongue on P10 usually covers about half of the inner web, though this can be up to 2/3 in a few. The tongue can be concave or rectangular in shape. Nearly all birds have black down to P4 or P3. Black band at tip of P10 is usually complete and thick. Adults are very white-headed even in mid-winter, and have bright yellow legs and feet, especially from February on.
So far for the theory.
Now, what are these then?
Bird 1. An adult gull with dark grey upperparts and Caspian-like structure, thus suggestive of Steppe Gull, but note the pinkish tinge to legs and, especially, feet, more like Heuglin’s Gull.
The same bird, stretching its wing. Unlike Heuglin’s Gull, black on P8 falls clearly short of primary coverts. The pale tongue on underside of P10 covers about 50% of inner web and is concave in shape (diagonal in Heuglin’s).
Bird 2. Another very similar mystery gull, Poti. First view is strongly suggestive of Steppe Gull.
View of the upperwing of this bird. The primary pattern looks ok for Steppe as well as Heuglin’s Gull here.
From below, however, the pale tongue on P10 has a concave shape, unlike Heuglin’s Gull. The pink feet and greenish tinge on legs are not typical of Steppe Gull.
Bird 3. This bird has bright yellow legs, but the fairly extensive brown spotting on head is unlike Steppe Gull. The bluish-grey mantle colour seems a bit too pale for Heuglin’s Gull.
In flight, the pale tongue on underside of P10 is too long for both Steppe and Heuglin’s Gull. In fact, it is as long as in the Caspian Gull to the right of it! Note also the large white mirror on P10, with broken black distal band (at least on left wing). Black only reaches down to P5; the inner four primaries are unmarked. Black on P8 falls short of the primary coverts.
And it goes from bad to worse. Bird 4 has head streaking that is so extensive that it matches Herring Gull. Yet, its upperparts are as dark grey as in Armenian Gull, and black on P8 reaches the primary coverts (just visible below the tertials here). The big white mirror on P10, with very little distal black, is unlike Heuglin’s and Steppe Gull.
Bird 5. Another barabensis type with way too big white mirror on P10.
There is very little distal black on the P10 mirror, and the feet have a pinkish tinge.
Still the same bird. Note that the strong contrast between dark grey remiges and white underwing coverts differs from Caspian Gull – if anyone was wondering about that species here.
Bird 6. With its bit of head streaking and short, fairly diagonal tongue on P10, this bird suggests Heuglin’s Gull at first.
From above though, the upperwings are rather pale and bluish for that taxon, and the black colour of P8 and P9 falls short of the primary coverts.
Birds 7 (left) and 8 (right). Two heuglini types, seemingly…
In flight, however, neither of these two birds truly matches Heuglin’s Gull. In the left bird, the pale tongue on P10 is way too long (longer even than in Steppe Gull) and has a concave shape, while in the right bird black on P8-9 falls clearly short of the primary coverts.
Another look at bird 8 in flight. The pale tongue on P10 has a concave shape, unlike Heuglin’s.
Bird 9. Big white mirror on P10, almost without any distal black. The black wingtip is quite restricted: black only reaches down to P5, and on P8-9 it falls clearly short of the primary coverts.
The underwing of bird 9. The pale tongue on P10 is extremely long and suggests Caspian Gull, but note the dark grey colour of the remiges as well as different head structure.
The following two birds seem to match Steppe Gull in all respects. They were seen above the landfill just south of Batumi on February 2nd. If they truly are Steppe Gulls, they would represent the first records for Georgia, which is over 1,200 km northwest of their normal wintering range.
Bird 10. Putative Steppe Gull, Batumi.
Bird 10, upperwing. Note bright yellow legs, clean white head and neck, thick black distal band on P10, black wingtip reaching down to P3. Bluish-grey upperwing.
The tongue on P10 is rather short and diagonal. Remiges paler grey than in Heuglin’s Gull, not contrasting strongly with white underwing coverts.
Bird 11. Putative Steppe Gull, Batumi. The pale tongue is rather long and could also match Caspian Gull, but there is no white mirror on P9 and black reaches down to P3. There is a thick black distal band on P10.
Bird 11, upperwing.
What does it all mean?
In 11 days time, we saw over 30 adult ‘misery gulls’ in Georgia. These seemed to show mixed characters of Heuglin’s and Caspian Gull, thus making them similar but not identical to Steppe Gull. It is difficult and probably unwise to try to pigeonhole such birds. Heuglin’s Gull is a tundra breeder, and its breeding range is well separated from the much more southern range of Caspian Gull, so extensive hybridisation is not likely. Perhaps some Herring Gull genes are involved, but that is just speculation. Whatever these birds are, it is clear that they make the identification of out-of-range barabensis more challenging. Another complication is that the breeding range of barabensis overlaps with that of Caspian Gull to some extent, and it may even come into contact with that of Heuglin’s Gull. Between the known breeding ranges of the latter and Steppe Gull lies an area of approximately 1,200 – 1,500 km wide impenetrable bogs and marshes; nobody really knows what is really going on there… At least, extensive intermingling of barabensis and cachinnans characters is known from northeastern Kazakhstan, and the same may be happening with Heuglin’s Gull.
One more possibility to consider when faced with such gulls as in Georgia is Taimyr Gull (Larus fuscus/heuglini taimyrensis). This is a very unlikely option though, as colour-ringing has shown that the gulls of the Taimyr peninsula move southeast to winter along the Pacific coast of East Asia. In addition, the tongue on P10 in this taxon is not longer than 50%, and there is always a substantial amount of black at the tip of this primary. Since some of the Georgian ‘misery gulls’ have a very long tongue and a big white mirror on P10, they do not match the appearance of Taimyr Gull.
As a final note, such ‘misery gulls’, of course, may also occur in other regions. There have been reports of Steppe Gull from Israel and even Greece; are these truly Steppe Gulls? Even some of the “Heuglin’s Gulls” photographed in Israel seem odd, and do not really match birds from the breeding range. For example, http://gull-research.org/heuglini/heug5cy/admarch06.html shows a huge, concave tongue on P10, and http://gull-research.org/heuglini/heug5cy/adfeb01.html portrays a bird with rather paler grey upperparts, big white mirrors on P9-10, and black of P8-9 clearly falling short of the primary coverts.
If you are still reading this, congratulations and thank you for your attention! Let us keep an open mind about these heuglini and barabensis types.