Wednesday, 21 December 2016

A beginners guide to Heuglin's gull in Cyprus, in particular the moult of a presumed 3cy at Lady's Mile.


First off....
I am no gull expert. These are the notes of a student not a master. Perhaps I have misunderstood everything, and all of this may be completely wrong and I'll get a grade D for effort. Before I went to Cyprus in 2016 I'd never even heard of Heuglin's gull and I knew very little about gull taxonomy or moult. However, since seeing Heuglin's gull in Cyprus I have researched the subject for my own interest and as I found out more, I got drawn ever deeper into it, and decided to put together these few notes which are really for my benefit to help me collate, summarise and remember, but they may prove to be of help and interest to other birders visiting Cyprus in winter, in which case that's a bonus.

I found two invaluable internet resources,  the Gull Research Organisation website and the Facebook group "Western Palearctic Gulls", both with many real gull experts who have a far greater knowledge of the subject than I, and who are generally all keen to help. The main book I have used is "Gulls of Europe, Asia and North America" by Klaus Malling Olsen and there is  paper by Valery Buzen published in British Birds in 2002. A full list of references are at the bottom of this post.

What is a Heuglin's gull?
Heuglin's gull is also sometimes known as Siberian, or West Siberian gull. It is very like the lesser black-back gull Larus fuscus graellsii which breeds in the UK and is most often considered a subspecies of lesser black-back, and on such occasions is given the scientific name L.f Heuglini. Some authorities refer to it as a seperate species (Buzun 2002, Olsen 2004, Gull Research Organisation) in which case it is referred to as Larus Heuglini, and that is the approach I will be adopting here.

The species breeds on Arctic tundra from northern Russia to north-central Siberia, and winters from east Africa, through the Middle East and into Asia. I don't remember hearing about them at all in December 2014 when I last visted Cyprus, including Lady's Mile, but in the lead up to this years holiday (December 2016) they were occasionally being reported on the BirdLife Cyprus recent sightings page and that was how I first became aware that the species even existed.

Seeing Heuglin's gull in Cyprus
I went to Cyprus thinking that I had absolutely no chance of picking out a Heuglin's gull due to the difficulties in seperating the species from lesser black-back gull, a problem only likely to be exacerbated by my lack of a telescope in Cyprus. What I didn't realise however, until I got there, was that Heuglin's is the only "black-backed" gull which occurs in Cyprus during the winter, and therefore it was actually one of the easiest gulls to identify of those present. Then when I realised that Heuglin's gull was just another name for the species I knew of as Siberian gull, it suddenly went from being a no-hoper to a major target species, because on a holiday where I didn't expect to get any new birds, I was presented with a great oportunity to get a difficult Siberian species "under my belt" and onto my Western Palearctic list without having to work too hard!


My initial contact with Heuglin's gull was at Mandria, near Paphos. I had been told that they occured here, most often sitting on the sea off Timi beach with Armenian, Caspian and yellow-legged gulls, although they could sometimes also be seen feeding on the arable fields close by and in windy conditions they would occasionally come onto the beach.


I visited Mandria on three occasions hoping to get a decent view of a Heuglin's gull, but unfortunately the flock was always on the sea, and without a scope the best I could say was that there was a "black-backed" gull with the flock, which in Cyprus in winter was almost certainly a Heuglin's gull. Very unsatisfactory for a Western Palearctic tick. However there are other clues to the identity of the "black-back" in the above photo. For example, it's clearly a huge bird, much larger than the herring gull sized Armenian gulls with which it is associating, and notice in particular the size of it's head when compared to the other gulls, whilst the slate grey mantle colour immediately rules out great black-back (which in any case doesn't occur in the Mediterranean and certainly not anywhere near Cyprus).

Fortunately it was a different story at Lady's Mile near Limassol. Here if you stay in the car you can get really close to the birds as they roost on the saltmarsh adjacent to the beach, and they are a mixture of Armenian, Caspian and yellow-legged gulls, in amongst a few hundred black-headed. I visited Lady's Mile on three occassions, and on the last occasion (12th December 2016) I came across a 3rd calendar year (3cy) Heuglin's gull and later an adult. Both  were quite close and photogenic, but the 3cy especially was very obliging and I managed to get a series of photographs which were the subject of much debate on the Facebook group "Western Palearctic Gulls".

I should mention at this point that Baltic gull L.f fuscus also occurs in Cyprus, but only as passage migrant, not a winter visitor. Baltic gull has a moult similar to Heuglin's, but it is smaller and in adult plumage it can be discounted because it has a blackish mantle unlike the slate grey of Heuglini.

3cy Heuglin's Gull at Lady's Mile.


This awesome looking bird was the first of the two Heuglin's gulls I found at Lady's Mile, and it was my bird of the holiday this year, even better than the adult in my opinion. What a beauty! Typical of the species it appears large headed, with a stout, angular bill. Some individuals can approach great black-back in size, as you can see in the photo from Mandria above, but this bird was a bit smaller than that.


There was a debate on "Western Palearctic Gulls" about whether or not this was actually the Scandinavian race of lesser black-back intermedius or perhaps even a hybrid, partly due to the extent of the streaking on the head and the very dark mantle (compare mantle colour to that of the adult below), but ultimately the general concensus was that it is a Heuglin's gull.

To put it into context, as I've already said, Heuglin's is the only regularly occuring "black-backed" gull in Cyprus in winter, whereas intermedius has thus far never been recorded, and therefore this would have been a first record for Cyprus if accepted as intermedius, so on balance of probability alone it's Heuglin's. However, there are other good reasons why this is Heuglin's gull, and moult is one such reason. To quote the Gull Research Organisation, "Heuglini, being a north Russian tundra breeder, can normally be identified by the late moult process in winter". 



At this point you can close the book if you like. You can see from this photograph that the bird is very retarded, with its moult nowhere near complete. It looks very tatty, with several brown, old (unmoulted) feathers. This is good enough evidence that this bird is a long distance migrant and therefore in Cyprus, in winter, it is most likely to be a Heuglin's gull. However, read on if you want a little more detail about the moult and ageing of this bird....


The timing of the moult of this bird is important in helping to determine the identification, because it gives a good indication of whether or not the bird is a long distant migrant. By the middle of December, most of the other large gulls at Lady's Mile are well on the way to completing their moult if it is not already complete, but this bird is still in the process of moulting from it's 2nd generation (2cy) feathers, into its new 3rd generation (3cy) feathers. The 2nd generation feathers stand out clearly  in these photos because they are brown and rather tatty looking when compared to the fresh dark grey or black 3rd generation feathers. You can see in this photo that the 2nd generation feathers yet to be moulted are P9-10 and most of the secondaries. Also, if you count the primaries you can see that P8 is missing on both wings and has recently been dropped and has not yet regrown.

In otherwords, even by the middle of December P9 & 10 have yet to be moulted and the moult of the secondaries has only just begun, a good indication that this is a long distance migrant. Heuglin's gull breeds in Siberia, begins its moult on the breeding grounds, but the moult is suspended at P4 in September in order to allow the gull to migrate to its wintering quarters around the Middle East. When the bird reaches it's wintering grounds the moult resumes.

As an aside, notice how fresh and pristine the already moulted 1cy Armenian gull looks behind, with no tatty or missing feathers.


The above photo shows well the late moult of this bird. Unlike most (but not all) lesser black-backs, Heuglin's gull has a late moult. On this bird you can see that whilst P1-6 are fully grown 3rd generation feathers, P7 is still growing, P8 is missing and P9 and P10 are brown 2nd generation feathers which have not yet been replaced. P10 is the last primary to be replaced and this is not completed until between January and early April. The bird will not drop P9 until P8 is well on the way to being replaced, and likewise P10 will not be dropped until P9 is almost fully grown. Therefore it's likely to be still some time before this bird completes its moult.

I was at first unsure as to how you can tell that P8 is missing. It is because the primaries moult in order, P1 to P10, and this bird has a missing primary (this is not obvious, but count them, there are only nine on both wings, there should be 10. Don't count the 3rd gen secondary as P1, I made that mistake!). Therefore, if P7 is still growing (you can see that it's too short, this is especially obvious on the left wing), then if the next feather is longer and full grown, it must be a 2nd generation feather and cannot be P8, because P8 would not start growing until the regrowth of P7 is almost complete. This is important because in the British and Scandanavian races of lesser black back (graellsii / intermedius), full moult of the primaries is usually completed by December.

The secondaries don't start moulting until the primaries have gone beyond P4-6. Therefore since this Arctic gull suspends its moult at P4 until after it has reached its wintering grounds, the secondaries don't even begin to moult until very late in the season and full moult is sometimes not complete until the end of April. On this bird, the inner secondaries are all missing, the central secondaries are 2nd generation and unmoulted, then there is a missing secondary followed by the only new and fully grown 3rd generation secondary which is the one adjacent to P1.

All of this clearly shows that this bird is a long distance migrant. Whilst on an individual bird this is not conclusive and does not prove that this bird is Heuglin's (e.g. other long distance migrants such as Baltic gull and perhaps even far northern intermedius also have a late moult), it certainly adds weight to the identification of a "black-backed" gull at Lady's Mile in December as Heuglin's gull.

For further thought
As discussed above this bird is generally thought to be a 3cy type Heuglin's gull, moulting from it's 2nd generation to 3rd generation feathers (in otherwords when it completes it's moult it will be in 3cy plumage). However I have a completely unsupported theory that the bird is actually a 4cy type moulting from its 3rd generation to its 4th generation feathers (i.e. when it completes it's moult it will be in 4cy (sub-adult) plumage).  My reasoning is as follows.

If this was a typical short distance migrant such as L.f graellsii, then the bird would have more or less acquired it's full 3cy plumage by the end of its 2nd calendar year, i.e. by the end of December it would look like a fresh 3cy bird. However since this bird is a Heuglin's gull with a very late moult, it doesn't acquire its 3cy plumage until the end of winter, perhaps not even until April. Therefore if this gull was currently moulting into its 3cy plumage, I would have expected it to show more 2cy features, such as signs of immaturity in the upperwing coverts and for it to have at least the remnants of a dark subterminal band on the tail. In fact the bird shows signs of neither, with a completely slate grey mantle and a pure white tail. 

Furthermore, when I posted these photos on the Facebook Group Western Palearctic Gulls, some people expressed surprise at how retarded the bird was in its moult, even for Heuglins gull, while others commented on the exceptionally streaky head, the latter feature in particular causing some to suggest that it may be intermedius. However, 4cy Heuglin's is said to have an extremely retarded moult, but has many adult features including slate grey upperparts and with extensive dark bold head streaking (Harris et al, 1996), all of which fits nicely with this bird, and helps explain the resemblance to intermedius. To my mind, all of this adds up to a bird about to enter it's 4th calendar year rather than its 3rd.

If anybody has an opinion on this please let me know via a comment, I'm keen to keep this post as accurate as possible.

Adult Heuglin's Gull at Lady's Mile


After I'd seen and photographed the 3cy, I retired to the nearby taverna for a celebratory coffee and a bowl of olives. I know how to live life! Thankfully I then decided to have another look through the gull flock, only to find that the 3cy had gone and had been replaced by this adult Heuglin's gull, which showed equally well, though I couldn't manage any open wing photographs. Notice the slightly paler mantle, more typical of Heuglin's gull and far too pale for Baltic gull which would appear almost completely black.


Adult Heuglin's gull.




Adult Heuglin's gull (left) with 1cy Caspian Gull and black-headed gulls for size comparison. Although some Heuglin's gulls can approach great-black back in size, with the largest Heuglin's bigger than the largest Caspian, there is much variation and I assume that in this case the adult Heuglin's is a female, whilst the 1cy Caspian is probably a male.


Associated blog posts
Watching wintering gulls in Cyprus - A Field Notebook, Colin Davies

References
Gulls of Europe, Asia and North America, Olsen K.M (2004)
The MacMillan Birder's Guide to European and Middle Eastern Birds, Harris et al (1996)
Descriptive update on gull taxonomy:‘West Siberian Gull’ Buzun V.A British Birds 95 (May 2002 pages 216-232)
Gull  Research Organisation website, accessed December 2016 
Western Palearctic Gulls Facebook group (Closed Group)
BirdLife Cyprus recent sightings page, accessed December 2016

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