Category Archives: Gull ID

American Herring Gull – in the Netherlands?

Peter Adriaens

A subadult Herring Gull photographed in the Netherlands seemed very unassuming at first, but actually shows a key feature for American Herring Gull. This feature may not be what you regularly check in gulls, and is very easy to overlook…

When Leon Edelaar sent me the following pictures of a “herring gull sp.” that he had photographed at Ijmuiden, the Netherlands, on 2 February 2013, I was very hesitant to put a name to it. The pictures had been gathering dust on Leon’s hard drive, but they recently sparked his attention because he noticed a “grey mirror” on the underside of the ninth primary (see American Herring Gull: new ID feature), which made him wonder…

Herring Gull sp., subadult, Ijmuiden, The Netherlands, 2 Feb 2013 (Leon Edelaar). Note oval-shaped, blackish patch on upper tertial.

Herring Gull sp., subadult, Ijmuiden, The Netherlands, 2 Feb 2013 (Leon Edelaar). Note oval-shaped, blackish patch on upper tertial.

Herring Gull sp., subadult, Ijmuiden, The Netherlands, 2 Feb 2013 (Leon Edelaar). Another view of the blackish ‘ink spots’ on tertials, from a different angle.

Herring Gull sp., subadult, Ijmuiden, The Netherlands, 2 Feb 2013 (Leon Edelaar). Another view of the blackish ‘ink spots’ on tertials, from a different angle.

At first sight, the bird in the pictures did not strike me as very unusual. Surely, in shape and overall plumage aspect, it looked rather like any run-off-the-mill (subadult) European Herring Gull!? However, a closer look reveals a few interesting features. At rest, the bird shows quite impressive blackish and oval shaped ‘ink spots’ on the tertials, while the rest of the plumage looks basically adult. Many European Herring Gulls show dark marks on tertials, of course, but it is quite rare to see one that looks adult except for such large, oval shaped and well-defined, black(ish) spots. That is something much more commonly seen in American Herring Gulls. Then, in flight, the bird reveals an isolated grey spot in the black pattern on underside of primaries (at least in right wing). Again, this is more common in American Herring Gull. So far so good. An interesting bird, yes, but nothing impossible for a European Herring Gull. However, then we look closely at the secondaries, and they show the most alarming feature: two small but well-defined black ‘ink spots’. Such isolated black spots on adult secondaries are not seen in European birds, and have been considered a key feature of 3rd and 4th cycle American Herring Gull ever since the identification paper by Mullarney and Lonergan (2004).

Herring Gull sp., subadult, Ijmuiden, The Netherlands, 2 Feb 2013 (Leon Edelaar). Black ‘ink spots’ on adult-like secondaries (here indicated by black arrows), and “grey mirror” on underside of P9 (white arrow).

Herring Gull sp., subadult, Ijmuiden, The Netherlands, 2 Feb 2013 (Leon Edelaar). Black ‘ink spots’ on adult-like secondaries (here indicated by black arrows), and “grey mirror” on underside of P9 (white arrow).

Other characters are less helpful. The primary pattern includes a complete, black ‘W’ on P5, and black “bayonets” on P6-7 (see Adriaens & Mactavish 2004) – good for American Herring, but equally possible for European birds. The tail shows a few small, solid black spots – better perhaps for American birds, as blackish markings in the tail usually do not look very solid in subadult European Herring Gulls. The bill shape and length look ok to me for either species, as does the colour of the upperparts. I would have expected heavier brown blotching on the neck and breast for an immature American Herring Gull, but there is a lot of variation.




Herring Gull sp., subadult, Ijmuiden, The Netherlands, 2 Feb 2013 (Leon Edelaar). The above four pictures show the primary pattern and pattern on tail.

Herring Gull sp., subadult, Ijmuiden, The Netherlands, 2 Feb 2013 (Leon Edelaar). The above four pictures show the primary pattern and pattern on tail.

So what does it all mean? It seems that, on current knowledge and for the time being, this bird should be considered an American Herring Gull, even though it is certainly not an obvious example! Here is one from North America that is similar:

The identification of such birds relies heavily on the pattern of the secondaries. There are many people closely studying and ringing gulls in the Low Countries, and it seems that such a pattern has never been documented in the local Herring Gulls.

If anyone has ever photographed such a secondary pattern in argenteus or argentatus, both Leon and me would be very interested to hear from you…

Calls of Thayer’s, Kumlien’s and Iceland Gulls

Peter  Adriaens

First off, a very warm welcome to new Birding Frontiers team member, Peter Adriaens. Read his biog and see his remarkable photo at the end of this post 🙂

Interminable debates have surrounded the identity and taxonomy of Thayer’s, Kumlien’s and Iceland Gulls of Arctic Canada. Until now, most of these have focused on plumage similarities and differences. Having obtained recordings of Kumlien’s Gulls in Newfoundland in early 2013, comparison could then be made between all 3 taxa. The long call of gulls is effectively their ‘song’. When the flight calls and especially long calls of the 3 are compared, the results are unexpected and surprising…

While our knowledge of birds in general has increased exponentially over the last few decades, it seems that some gull taxa have managed to remain a mystery. This is particularly true for the “Iceland Gull complex”. The taxonomic position of Thayer’s Gull, Kumlien’s Gull and Iceland Gull is a much discussed topic, but for the last 15 years or so, the debate seems to have been going in circles rather than forward. It may even be going backward: indeed, Snell (2002) in ‘Birds of North America online’ treats the three taxa as just one, monotypic species, Larus glaucoides. Thus, we are led to believe that gulls with white wing tips (glaucoides) living in Greenland are the same taxon as gulls with black wing tips (thayeri) living in western North America, 2,000 to 5,000 km further away. Convenient perhaps, but a bit despondent surely?

The debate is characterised by many unanswered questions and a lot of speculation. To add something more informative, I would like to draw attention to the calls of these taxa. For display, large gulls have a “long call” that is unique to each taxon. It is effectively the song of a gull, and consists of three separate stages, the third one being a long, loud series of fairly short, staccato notes. One thing that the three “Iceland Gull taxa” have in common, is that the staccato notes of the long call are delivered more slowly than in other large gulls: there are usually only two staccato notes per second, as opposed to four in, e.g., European or American Herring Gull. For a recording and sonogram of a displaying pair of the latter taxon, have a look at the recording >>>HERE<<< and note that about 3.5 – 4 staccato notes are delivered per second (from seconds 3 to 7), at a frequency of c 1000 to 4000 Hz.

Yet, there are noticeable differences between the three “Iceland Gull taxa” as well. Recordings have become available in recent years, except for Kumlien’s Gull, so I recorded this taxon myself in Newfoundland in January and February 2013. When discussing these recordings with Magnus Robb, it became clear that especially Thayer’s Gull is somewhat different. While gull long calls are variable, e.g. differing between male and female and depending on the kind of interaction that is going on, the difference may be significant, and has actually been hinted at before: Sibley (2000) described the long call of Thayer’s Gull as lower and flatter than (American) Herring Gull, while Iceland Gull is said to be ‘shriller’ (i.e. higher).

 Thayer’s Gull

Thayer' s Gull (near) adult Choshi, Japan, 11th March 2013. Peter Adriaens

Thayer’ s Gull (near) adult Choshi, Japan, 11th March 2013. Peter Adriaens

So what do these birds sound like? The Macaulay Library has three recordings of adult Thayer’s long calls and two of flight calls. You can listen to them >>> HERE <<< . As the recordist also comments, these calls sound rather deep. If we put this into a sonogram, we can see that the fundamental (i.e. lowest) staccato notes start below 1000 Hz and have a rather flat, gently arched shape. There are also some guttural sounds, which go below 500 Hz.

Adult Thayers Gull, flight calls & long calls. Churchill, Canada 3 June 2009 (from Macaulay Library)

Adult Thayers Gull, flight calls & long calls. Churchill, Canada 3 June 2009 (from Macaulay Library)

Note also that the flight calls sound quite low, starting clearly below 500 Hz.

Thayer's Gull (near) adult, Choshi, Japan, 11th March 2012. Peter Adriaens

Thayer’s Gull (near) adult, Choshi, Japan, 11th March 2012. Peter Adriaens

Another recording of Thayer’s Gull long call is available on the Stokes CD ‘Bird songs of West America’. Again, the sonogram shows deep staccato notes (starting below 1000 Hz) with a flat shape.

Thayer' s Gull long call from Stokes CD ‘Bird songs of West America’.

Thayer’ s Gull long call from Stokes CD ‘Bird songs of West America’.

 Iceland Gull

Adult Iceland Gull, Grindavik , Iceland, 28 March 2010. Peter Adriaens

Adult Iceland Gull, Grindavik , Iceland, 28 March 2010. Peter Adriaens

Compare the Thayer’s Gull calls above to the following recording of a displaying adult Iceland Gull (nominate glaucoides), made by Magnus in Iceland in spring:

Transferring this to a sonogram reveals that the call notes have a distinctly peaked shape, are all clearly above 1000 Hz and therefore higher pitched than in Thayer’s Gull:

Adult Iceland Gull long call, Iceland, Magnus Robb

Adult Iceland Gull long call, Iceland, Magnus Robb

Goethe (1986) based on several hundreds of recordings made in breeding colonies in Greenland and on birds in captivity, also describes the long call of adult Iceland Gull as higher than 1000 Hz. He also found it to be 500 to 700 Hz higher than in Herring Gull.

Adult Iceland Gull, Grindavik, Iceland, 23 March 2010. Peter Adriaens

Adult Iceland Gull, Grindavik, Iceland, 23 March 2010. Peter Adriaens

Further recordings of nominate Iceland Gull can be found on commercial CDs such as Schulze’s ‘Bird Songs of Europe, North Africa and the Middle East’ – though the long call on there is that of an immature bird.

Flight calls can be heard from about the 24th second in Magnus’ recording (first recording above and in short section extracted in 2nd recording directly above). These sound higher pitched than in Thayer’s Gull. In the sonogram, they are clearly above 1000 Hz:

Adult Iceland Gull flight call, Iceland. Magnus Robb

Adult Iceland Gull flight call, Iceland. Magnus Robb


 Kumlien’s Gull

Adult Kumlien's Gull Newfoundland, 22nd January 2013. Peter Adriaens

Adult Kumlien’s Gull Newfoundland, 22nd January 2013. Peter Adriaens

The long call of Kumlien’s Gull seems similar to Iceland Gull, though perhaps sounding even higher – which is a bit unexpected in a taxon that is seen as intermediate between Thayer’s and Iceland Gull, or even as a hybrid between the two by some. In any case, the long call is clearly higher than in Thayer’s Gull, with the fundamentals starting above 1000 Hz. The flight calls sound higher pitched too; in the sonogram, they are at about 1000 Hz or higher, while Thayer’s flight calls start below 500 Hz already.

Long calls

Kumlien’s Gull adult Long calls (best 2) Newfoundland Jan- Feb 2013. Peter Adriaens

Kumlien’s Gull adult Long calls (best) Newfoundland Jan- Feb 2013. Peter Adriaens

Kumlien’s Gull adult Long calls (best 3) Newfoundland Jan- Feb 2013. Peter Adriaens

Kumlien’s Gull adult Long calls and Flight calls Newfoundland Jan- Feb 2013. Peter Adriaens

Kumlien's Gull adult Long calls (best 2) Newfoundland Jan- Feb 2013. Peter Adriaens

Kumlien’s Gull adult Long calls (best 2) Newfoundland Jan- Feb 2013. Peter Adriaens


Kumlien's Gull adult Long calls Newfoundland Jan- Feb 2013. Peter Adriaens

Kumlien’s Gull adult Long calls Newfoundland Jan- Feb 2013. Peter Adriaens

Adult Kumlien's Gull Newfoundland, 1st February 2013. Peter Adriaens

Adult Kumlien’s Gull Newfoundland, 1st February 2013. Peter Adriaens


Flight calls

Kumlien’s Gull adult Flight calls Newfoundland Jan- Feb 2013. Peter Adriaens

Kumlien's Gull adult Flight calls Newfoundland Jan- Feb 2013. Peter Adriaens

Kumlien’s Gull adult Flight calls Newfoundland Jan- Feb 2013. Peter Adriaens


 It seems interesting that Thayer’s Gull appears to have a deeper, flatter voice than Iceland, Kumlien’s and even Herring Gulls. While I fully realise that many more recordings are needed, especially from the breeding grounds, I simply hope that the above information provides a fresh look at an old problem. Perhaps the taxonomic debate cannot be settled by measuring skins in musea. There is still a need for more detailed and controlled research, which should probably also take into account voice and ecology. Thayer’s, Kumlien’s and Iceland Gull certainly behave like three distinct populations; each one has its own breeding and wintering range, for instance. Each one seems to have its own plumage traits (Howell & Elliott, 2001; Howell & Mactavish, 2003) and probably also voice. If the whole Iceland Gull complex is just one big cline, as suggested by e.g. Snell (2002), how can there be three distinct populations? And if Kumlien’s Gull is merely a hybrid, as advocated by e.g. Weir et al (2000), why does it have its own range? Surely the taxonomic debate can only be settled when there are firm answers to such questions.


 Goethe, F. 1986. Zur Biologie, insbesondere Ethographie der Polarmöwe (Larus glaucoides Meyer, 1822). Ann. Naturhist. Mus. Wien. 88/89(Ser. B):113-146.

Howell, S & Elliott, M T. 2001. Identification and variation of winter adult thayer’s gulls – with comments on taxonomy. Alula 7 (4): 130-144

Howell, S & Mactavish, B. 2003. Identification and variation of winter adult Kumlien’s Gulls. Alula 1: 2-15

Snell, R. R. 2002. Iceland Gull (Larus glaucoides), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online:…0.2173/bna.699

Weir, D. N., Kitchener A.C., and McGowan R. Y. 2000. Hybridization and changes in the distribution of Iceland gulls (Larus glaucoides/kumlieni/thayeri). J. Zool., London, 252: 517-530


Trickier birds would be very interesting to record…

Adult Kumlien's Gull (dark individual), Newfoundland, 25 January 2013. Peter Adriaens

Adult Kumlien’s Gull (dark individual), Newfoundland, 25 January 2013. Peter Adriaens


“As usual, I am fashionably late – even when it comes to joining something as interesting and thought-provoking as the website. I am honouredPeter Adriaens photo resize to now be part of a great team of blog writers, and I hope I can contribute something useful from time to time. I promise it will not always be about gulls! As an editor for Dutch Birding, I enjoy writing identification papers, but some topics and ideas probably lend themselves better to the blogging world than to a 25 page in-depth article. I live in Belgium, where I have had the good fortune to be able to work in gull and tern colonies for a few years. I have also worked in Armenia, surveying breeding birds and migration. I have traveled widely, mainly with the idea of becoming more familiar with some species that interest me. Birding has been my main passion for over 25 years and I still thoroughly enjoy it – be it when seeing a new bird or some kind of variation that I was not familiar with; it is all thrilling. If nothing else, it is often great to just be outdoors. Time spent in nature is never time wasted, as they say…”

(Photo taken just before entering a heavily polluted part of the Maasvlakte when we were ringing Common Terns…)

 Peter Adriaens, December 2013


Adult Thayer’s Gull

from Arctic Canada to Northwest Spain to County Donegal

eds. Thayer’s Gulls are often viewed in terms of both identification and taxonomy as the Gordian Knot of gulls. It  need not be so! Delighted to hear from Derek C. of his find at Killybegs. Co Donegal some 6 days ago. On circulating his photos, all agreed it was a bulls-eye ID. Dani L-V quickly picked up its similarity to a bird that has been visiting NW Spain on/off  since 2008. It was surely the same bird! It easily becomes the most well documented Thayer’s Gull in the Western Palearctic with photographs from juvenile plumage onwards. And we are already learning stuff from this one:


* all  plumages from juvenile to adult documented Western Palearctic vagrant.
* iris can go from dark to light to darker again. That’s new!
* the subtle changes in adult wing tip pattern after one moult
* learn bit more about movement of Nearctic  gulls in WP
* the Spanish get first accepted Thayer’s Gull record (come on Britain!)


by Derek Charles (with Dani López-Velasco)

The Donegal Bird


killybegs gull (1)

killybegs gull eye  head 2

killybegs gull wingtipIMG_0591 (1)

killybegs gull jettyadult Thayer’s Gull (5 years old), Killybegs, Donegal 15th December 2013, all photos above: Derek Charles. Bottom photos it is the right hand bird with argenteus Herring and a Great Black-backed Gull.

Hi everyone

I found this gull yesterday (15th Dec.) at Killybegs. The underwing was pale giving thoughts of Kumlien’s but the blackish primaries put that thought on the back burner and combined with the heavy shawl and dark eye had me thinking immediately of Thayer’s. Despite the dreadful conditions I managed some reasonable photos,

The primary pattern appears good. The small black band on p10 with tiny white tip, p9 a complete black leading edge with the mirror not spanning both webs and the small black band on p5 all are good for  Thayer’s. 

Additional pro Thayer’s features, raspberry pink legs (in flight and when dip feeding the pink feet were especially noticeable) hint of pink eye ring (not noticeable in field), dark mantle

I think it’s a pretty good candidate and feedback from local guys is positive for Thayer’s

All comments appreciated!


Hi guys!
 As I told Derek, I think both birds look very similar, and I am quite sure they are most likely the same individual. How exciting!!
 A few remarks:
  • First, the Spanish bird has just been accepted as the first for Spain. After several years of study, we´ve finally decided to go a step further and accept it, and it will appear published on the Spanish annual rarity report in a few days.
  • Wing pattern: I’ve compared both carefully, and just they look spot on; can’t find anything that suggests they´re not the same one. Check, on the right wing, the shape of the black subterminal band of p10-identical –  shape of the black W on p5-identical – shape of the black along the outer web of p10 when it meets the white mirror – identical… and so on
  • Bill: I’ve checked bill shape of both, and it just looks identical, especially the exact shape of the tip, as well as the nostril.
  • Eye: one of the things that seemed a bit ad odds with acceptance as a pure bird, when it showed up as a 3rd winter, was the paleness of the iris. OK, some can in theory show it, but still it was a bit extreme. But the interesting thing is that each year, as the bird has got older, the iris had clearly darkened. This past winter, in March, the eye looked quite dark at a distance, and when seen close up you can see that it has a lot of dark speckling. Thus, it’s quite possible that this winter the eye might have got slightly darker. The eye of the Irish bird is quite dark, but I think it could well fit with the Spanish bird, especially considering what I’ve just explained
  • The blotchy streaking around the neck seems denser and more profuse on the Irish bird, but of course its December, and we always see it in march, after having probably wintered somewhere quite sunny (e.g. Portugal or Morocco), so wear, together with partial body moult, can explain why the streaking of the Spanish bird is not as dense (although note that on some of the pictures I attach, it’s quite, quite similar indeed!)
 The Spanish bird, apart from having been seen once in December (see the attached file with all the sightings), always shows up in early March, and leaves by the end of March or early April. The area is checked quite frequently, and we are sure the bird doesn’t winter there (at least over the last 3 winters). We assumed the bird was wintering further south, and then on the way north, stopped at Lago-San Ciprian for a couple of weeks, before moving on. We were all hoping that the bird would get found in the UK sooner or later, but I was expecting that to happen in the spring..
What do you guys think??
Cheers Dani

Josh Jones has done a really good piece with more of Derek’s story and excellent photo analysis on the Birdguides webzine.

The Spanish Bird


cipri12 (1)ciprithis head shot by Pablo Gutierrez with thanks

cipri12 (2)

cipri5adult Thayer’s Gull, Galicia, March 2013 all photos above apart from head shot by: Antonio Martínez Pernas, with thanks

cipriana………Occurrences of the Thayer’s Gull in NW Spain from Feb. 2008 to March 2015.

Immature Plumages

Here it is in:

 >>> 1st  winter, 2nd winter and 3rd winter plumages <<<


Tiny changes in wing tip pattern

Though in essentially full adult plumage both last spring in Spain and this December in Co..Donegal, it has undergone a complete moult including all of its flight feathers. Martin Elliot working with birds in the Bristol area years ago clocked that even in adult plumage the wing pattern was not fixed. Broadly speaking with age, and sexual maturity, the amount of black decreased and amount of white increased. Dermot Breen has done a great job at going ‘forensic’ on the wings. The most parsimonious explanation is that it is the same bird. Nevertheless with close inspection there are subtle changes. There is a tad more dark in p5, and notably the outermost 2 primaries, p9 and p10 do have tad more pale/white and less dark. See Dermot’s excellent analysis below:


NEW LOOK to Birding Frontiers

All this marvelous Thayer’s Gull stuff seems a good opportunity announce the new, fresh look to ‘Birding Frontiers’. Coming very soon it will include pioneering information on Thayer’s, Kumlien’s and Iceland Gulls.You won’t have seen this stuff before. Promise! And there will be lots more.

To be cont’d…

Identification of first cycle Cape Gull

Identification of first cycle Larus dominicanus vetula:

The Cape Gull of Good Hope?

 by Chris Gibbins


The two Cape Gulls Larus dominicanus vetula recently found in Portugal (Birding World, 26(6), July 2013), along with the previous bird in Paris (Jiguet et al., 2004), illustrate that this is a species we should be looking out for in Britain.

Gull watching in Europe is perhaps best in the Northern hemisphere winter, because this is the time that Northern breeders move away from their breeding areas and displaced birds may find themselves on our shores.  For the same reason, the chances of finding Southern hemisphere taxa here may therefore be best in the months following their breeding season; i.e. in the Austral winter, our Northern summer.

All three European Cape Gulls have been adult or near adult birds.  However, given that younger individuals are more likely to occur here as vagrants, anyone keen to find a Cape Gull is perhaps best advised to have a working knowledge of what first cycle birds look like during the Northern summer. The aim of this note is to showcase this age group at this time of year, and highlight one or two features that should make them stand out among our local gulls. The main argument put forward is that because of their absolute age and related absence of primary moult, along with the presence of a remarkably striking secondary skirt, in the Northern summer first cycle birds offer good prospects for out-of-range identification – they are the Cape Gulls of good hope.

Taxonomy and terminology

 Before discussing identification, a few words on taxonomy and the terminology used in this note may be useful.

cape gull3

Cape Gull (vetula) is the African subspecies of the very widely distributed Kelp Gull Larus dominicanus.  So far it seems that all European records of Kelp Gull have been vetula (Jiguet et al., 2004), so at least for the moment this seems the most meaningful taxon to discuss.  All the photographs and observations upon which this note is based relate to birds observed in the SW Cape Province of South Africa between 26 June and 6 July 2013. Hence, all birds are assumed to be vetula.

 Comparing age classes of Northern and Southern hemisphere gulls is made complicated by respective breeding seasons.  Terms such as ‘first winter’, ‘first summer’ are confusing when comparing Southern and Northern species, because the seasons are effectively reversed. Moreover, because breeding times differ by around 6 months, at certain times of the year the use of calendar years does not work. For example, the laying period of Kelp is November-December (Jiguet et al, 2001) so by April first calendar year (1cy) birds will be a few months old, and so could conceivably turn up in Europe; however, there is no such thing as a 1cy Northern hemisphere gull in April (as laying has not even commenced and birds reared in the previous season have ‘ticked over’ into their second calendar year) so meaningful comparison using calendar years is not possible at this time.

The solution is therefore to talk about ‘cycles’ (as per Howell and Dunn, 2007).  A first cycle bird is defined here as a bird that has not completed its first primary moult. For Northern taxa this moult occurs in the summer of their second calendar year (e.g. in Scotland Herring Gulls start primary moult around 1 May), so first cycle birds in the Northern summer are around a year old.  In Cape Gull this primary moult commences in October-November, when birds are a little less than a year old.  The main advantage of using cycles when comparing immature Cape to our Northern gulls is that birds in the same cycle are the most likely cause of confusion, even though their absolute ages differ by several months.

cape gull1

Moult: Why we should not throw the baby out with the bath-water

Moult is often cited as being useful for field identification of gulls. Due to reversed breeding times, Southern hemisphere gulls such as Cape have completely different moult periods to Northern ones; they are in moult when our birds are not, and vice versa. This should make them look strikingly different.  However, the opposing argument is that displaced birds may adopt (or ‘correct’ to) the moult cycle of the birds in their new location. Indeed, Malling Olsen and Larsson (2003) specifically make this point in relation to Kelp/Cape Gull:

‘Note, however, that Kelp Gulls in the Northern hemisphere may adopt moult cycles similar to Northern hemisphere gulls, as has been observed in US and Mexican adults’ (p144)

The Paris Cape Gull supports this argument, as it was moulting in accordance with our Northern hemisphere gulls (Jiguet et al., 2004).  So perhaps we should abandon any thought of moult being useful for picking out a Cape Gull?

The Paris bird was an adult.  In theory it could therefore have been in the Northern hemisphere for several years; this is ample time both for it to need to adjust its moult to Northern seasons and be physiologically able to do this.  Younger birds, especially first cycle ones, by definition can’t have been here so long. A first cycle Cape reared in the austral summer will only be a few months old by the time the Northern summer comes around; unlike our birds whose primaries are a year old, a first cycle Cape should have much fresher feathers that do not need replacing, and in any case if it has only just arrived, it may not be physiologically capable of moulting feathers rapidly enough to catch up to our first cycle birds (i.e. our 2cy, ‘first-summer’ gulls; Table 1).

So, while we should always be careful when using moult, in the Northern summer it seems likely to be more useful for first cycle Cape Gulls than adults.  In addition, as birds may be more prone to be displaced or wander in their first year of life, the Northern summer is likely to be a productive time for first cycle Cape Gulls in Europe.  At this time, because they will only be a few months old, their moult and extent of feather wear and bleaching should be markedly different to our birds.

cape gull2 june 13

Picking out a Cape Gull

The starting point for picking out a Cape is to be familiar with first cycle Northern gulls during the summer when they are moulting primaries. A safe window for picking out a Cape would be May-August inclusive, as this covers the start and mid part of the moult period of Northern taxa, but is well before first cycle Cape Gulls might be expected to drop their first primary (Table 1).  Because of feather grey tones and the inner primary patterns (detailed later) first cycle Lesser Black-backed Gulls (LBBs) are most similar to Cape, but actually the key distinguishing features suggested here also apply to separation of Cape from Herring and Yellow-legged Gulls.  Plates 1-3 show what a typical first cycle graellsii or intermedius LBB looks like in mid summer, while Plate 4 shows a Yellow-legged Gull. The key points to note in these images are the extreme wear on remaining first generation primaries and wing coverts and the fact that birds are in primary moult.

The Full Article

This blog post is a taster to full article fully illustrated with Chris’s fab photos and available as a pdf.

Just download the PDF below.

>>>> Identification of first cycle Cape Gull <<<<


American Herring Gull: New ID feature

A new feature for identifying adult American Herring Gull

by Peter Adriaens

Gulls never cease to amaze me. You can be studying one species for over ten years, and still find that you have overlooked something that was right in front of your eyes all this time. This is what happened to me when I came back from my second trip to Newfoundland, Canada, a few months ago and started studying my photographs.

Identification of American Herring Gull (in a European context) has been dealt with by Lonergan & Mullarney (2004) and Adriaens & Mactavish (2004). To all of the identification features described in those papers, a new one should be added, namely that of a grey ‘mirror’ on the underside of the outermost primaries. More precisely, this is a sort of isolated grey spot or grey hole inside the black(ish) pattern on the underside of P9 or P10 (see photos). It looks like a promising and easy feature for distinguishing between adult American and European Herring Gulls, though with some caveats.

The good news is that the grey ‘mirror’ is easily visible in the field (sometimes even on a standing bird), that it is seen in birds across the whole of North America (so not just in Newfoundland), and that it is rare in European Herring Gulls, perhaps mainly occurring in birds with medium to dark grey upperparts (i.e. slightly darker than American Herring Gull). The bad news is that it is shown by only a minority of the American birds, and that a few hybrids (or backcrosses) of Glaucous and Herring Gull in Iceland show it too, thus creating a serious pitfall for the unwary. A distinction should also be made between a grey ‘mirror’ – which is completely surrounded by the black colour of the feather – and a grey cut, which is not isolated (e.g. open at the feather edge; see plate 20 and 21). The latter pattern occurs regularly in both American and European Herring Gulls.

So, how many adult birds show this grey ‘mirror’ in North America? A quick analysis revealed the following proportions:

–          Newfoundland: 58 out of 340 (= 17%)

–          California:         14 out of 164 (= 9%)

Isolated grey ‘holes’ are therefore only shown by a small minority, and become probably scarcer towards the west of the continent, but when present they could serve as an indication for American Herring Gull and any bird with pale grey upperparts that shows this pattern may well be worth closer scrutiny. Especially those birds in which the isolated grey spot has a neatly rounded shape look distinctive. Nevertheless, it is always necessary to use as many characters as possible to clinch the identification.

In Europe (including the Azores), at least one claimed adult American Herring Gull has shown the pattern, namely the bird that has been wintering in Galicia, Spain, for at least six winters now. This bird shows an isolated grey ‘hole’ on the underside of P10 of the right wing (see here)

dnplate 1. Underwings of American Herring Gull (left) and argenteus Herring Gull (right). Note small, isolated grey spot on P9 in left bird. Photo left taken at St John’s, Newfoundland, in April 2000 (Bruce Mactavish); photo right taken at Heist, Belgium, in April 2011 (Peter Adriaens).

dn (1)plate 2. Adult American Herring Gull, St John’s, Newfoundland, 26 Jan 2013 (Peter Adriaens). A bird with typical primary pattern, including a small, isolated grey spot on underside of P10, just in front of the white mirror.

dn (2)plate 3. Adult American Herring Gull, St John’s, Newfoundland, 23 Jan 2013 (Peter Adriaens). The isolated grey ‘mirror’ can be visible even at great distance.

dn (3)plate 4. Adult American Herring Gull, St John’s, Newfoundland, 23 Jan 2013 (Peter Adriaens). The isolated grey ‘mirror’ is very distinct in this bird (though lacking on right wing).

dn (4)plate 5. Adult American Herring Gull, St John’s, Newfoundland, 23 Jan 2013 (Peter Adriaens). Isolated grey ‘mirror’ on P9, just in front of the white mirror.

dn (5)plate 6. Adult American Herring Gull (with Kumlien’s Gulls, Black Ducks, and Greater Scaup), St John’s, Newfoundland, 24 Jan 2013 (Peter Adriaens). A rare example of a bird with two isolated grey ‘mirrors’ on P10.

FULL pdf download available:

Full paper contains many more photos of American Herring Gulls, comparative European Herring Gulls and Glaucous X Herring Gull hybrids.

To get your copy, click here:

 A new feature for identifying adult American Herring Gull

Peter Adriaens, April 2013

Thayer’s Gull in 2nd winter plumage

2nd winter plumage

Free Article Download

web cover page


Identification of Thayer’s Gull has been a hot potato for a long time, and remains so today. This photo-essay has been put together to encourage birders to look for second winter Thayer’s, an age group that has yet to be recorded in Europe, and to discuss identification criteria. Done in pdf format to download, print off, and use in the field etc…

Chris Gibbins and Martin Garner

We hope it is  a useful contribution to the subject.

click below to download, print off and try out!

CG_MG_Identification of second winter Thayers

Thayer’s Gull flight shots

more pics from yesterday

Showing its appearance in flight (from Mark the Pieman) and v nice pic from Paul Hackett. Some other frame fillers, which you may have seen but if not:  here.


Juvenile Thayer’s Gull, Elsham, Lincs, 6.4.12 by Mark Reeder

Juvenile Thayer’s Gull, Elsham, Lincs, 6.4.12 by Paul Hackett