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Thayer’s Gull in DenmarkHvide Sande HarbourFebruary 4, 2012

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Introduction

By presenting photos of different accepted Thayer’s Gulls and other species, I hope that I have been able to document that all characters questioned are within the variation of Thayer’s Gull

I acknowledge that single individuals could be misidentified and have thus tried to select several different individuals for each character in order to come around such issue

I hope you will find that the most parsimonious explanation for the Danish gull is that it is a Thayer’s Gull, as are most of the other ones which have occurred in recent years in western Europe, even though they vary somewhat in appearance just like the juveniles of all large white-headed gulls

I have used this mark to indicate the Danish gull when it is placed among other individuals in the following pages

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Evaluation of JIZZ and plumage:

When evaluating jizz and plumage one should always remember that single situation photos will not always do a bird justice

It is always best to make a judgement based on multiple photos capturing different posture/ behaviour/ situations. Keep that in mind when evaluating this record

Note the small-to-moderate gonydeal expansion typical of the species

The following list of pro-thayeri plumage characters support the ID:

1. relatively long primary projection2. primaries are dark, the darkest part of the plumage, though only a little darker than tertials3. primary tips are highlighted by narrow pale fringes, forming thin chevrons4. distinct dark peppering on inner primaries5. subterminal marks on inner primaries are pale and almost translucent6. silvery-grey underside of the primaries with dark trailing edge on outer primaries7. tertials exhibit complex pale patterning concentrated toward the feather tip8. greyish cast to tertial centres9. characteristic pattern to the juvenile scapulars with small brown centres and paler brown

internal colour10. extensive barring to the undertail coverts and uppertail coverts11. venetian blind created by the contrast between the inner and outer webs of the primaries,

i.e. obvious silvery-grey inner webs to outermost primaries12. distinct dark secondary bar13. secondaries have a thin, dark subterminal ‘arrowhead’ mark14. secondaries, especially outer most, are paler greyish brown15. bright pink leg colour16. relatively thin bill 17. pale eye-ring 4

Colour tone and white balance in digital photos:

Note that the Danish gull was mainly seen feeding in the shade on a very sunny day with a clear blue sky. In such a situation the natural light puts the automatic white balance in the digital camera on a test and often causes the cold colour tones to be exacerbated.

In the two photos below, the difference in appearance is striking and the automatic white balance fails and add to the salt-and-pepper impression. In real life, the Danish gull looked more warm and soft in plumage colours then the auto shows and when the white balance is set to shade, the digital representation matches the live bird

This is by the way a typical problem as also illustrated here:

http://www.elisanet.fi/antero.lindholm/Linnut/Acro/kuvien_varit/dum.html

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White Balance:set to shade

White Balance:set to auto

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Chequered wing coverts and upperparts:

People have argued that the irregular pattern on the greater coverts and the chequered upperparts are wrong for Thayer’s Gull even though identical patterns are also seen in several individuals in ‘Gulls of Europe, Asia and North America’ by Olsen & Larsson and ‘Gulls of the Americas‘ by Howell & Dunn. To illustrate that the pattern seen in the Danish gull is within what is fully accepted as being part of the Thayer’s Gull plumage variation, I have collected photos of other individuals with similar pattern

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Chequered wing covertsand upperparts:

-‘salt-and-peppered’ upperparts- identical primary projections- identical steps between exposed primary tips- similar leg proportions and leg length- primary tips with white edges

8Ontario, Canada (Photo: Kirk Zufelt) http://larusology.blogspot.dk/2009/11/thayers-gull.html

Washington (Photo: Charlie Wright)http://www.flickr.com/photos/potoo/6787890041/

California (Photo: Clay Kempf) http://www.pbase.com/ternvomitthief/thayers_gull_tutorial

-‘salt-and-peppered’ upperparts- identical primary projections- identical steps between exposed primary tips- similar leg proportions and leg length- primary tips with white edges

Chequered wing covertsand upperparts:

Choshi, Japan (Photo: Michiaki Ujihara) http://gulldk.blogspot.dk/2012/07/danish-gull-versus-thayers-from-japan.html

Ontario, Canada (Photo: Brandon Holden)https://picasaweb.google.com/117329578255897846071/KumlienSThayerSGullsFromONTARIO#

Chequered wing coverts and upperparts:

California (Photo: Hans Larsson)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

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California (Photo: Hans Larsson)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

California (Photo: Hans Larsson)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

California (Photo: Peter Adriaens)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

Chequered wing coverts and upperparts: 10

Massachusetts (Photo: James P. Smith)http://pioneerbirding.blogspot.dk/2008/01/thayers-trio-cape-ann-ma-0113.html

Chequered wing coverts:

Oregon (Photo: Greg Gillson)http://nwbackyardbirder.blogspot.se/2012/01/separating-first-winter-thayers-gull.html?spref=tw

California (Photo: Ian Bousted)http://www.surfbirds.com/media/Photos/2002-05-02-thayersgull-ib4.jpg

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Chequered wing coverts:

England (Photo: Paul Hackett) http://birdingfrontiers.com/2012/04/07/thayers-gull-flight-shots/

Duluth-Superior area (Photo: Karl Bardon) http://www.pbase.com/karlbardon/image/120880969

but a similar pattern can also be shown by birds wintering away from the US west coast

and by the latest candidate from England

was also shown by theNorwegian bird

Norway (Photo: Alf Tore Mjøs)http://cyberbirding.uib.no/gull/tg/juv_01.php

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(Photo: Matt Brady)http://www.tertial.us/gulls/thay1.htm

Chequered wing coverts and upperparts:

Steve Hampton writes: ‘This is a dark, but nicely marked, bird. While the brown parts are rather dark, the patterning is still perfect for Thayer's Gull. November 30, 2010. Lake Mendocino, California’.

Note the almost identical upper-wing and the fresh frosty ‘salt-and-pepper’ plumage

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California (Photo: Clay Kempf)http://www.pbase.com/ternvomitthief/thayers_gull_tutorial

Chequered wing coverts and upperparts:

Note the pale eye-ring, flat forehead and almost identical upperparts

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California (Photo: Matt Brady)http://www.tertial.us/gulls/thay1.htm

Chequered wing coverts and upperparts:

Note the almost identical upperparts

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Head shape can easily vary depending on posture and behavior:

Resting on roof In feeding frenzy

In feeding frenzyIn feeding frenzy Resting on roof

The head profile changed dramatically between when it stood relaxed on the roof with a rather round head and gentle expression and when it feed with its wings continuously raised while balancing on the container edge and in constant combat with the nearby large gulls as in most photos

Great Black-backed Gull

Head shape can easily vary depending on posture and behavior:

Thayer’s Gull, 4th cycle16 December 2012Lake County, IllinoisPhoto: Amar Ayyash

Note how the head profile changes between when this Thayer’s Gull was standing relaxed with folded wings and when it suddenly raised its wings

Note the high rounded forehead and overall head shape

Note the flat crown and squarish head shape with convex eyebrow

Note the flat forehead and crown

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Long bill, flat head and snouty look:

I can understand that, in a Californian context, "large and snouty" is disconcerting. However, if you check images from the breeding range, it is clear that large, snouty structure with strong bill are perfectly normal in Thayer's Gull

See for instance these birds in the video from the northeastern tip of Baffin Island, Nunavut:

http://macaulaylibrary.org/video/400952/larus-thayeri-thayers-gull-canada-nunavut-timothy-barksdale

Strong focus on size and structure when identifying gulls in California may lead to a skewed bias towards small, thin-billed Thayer's Gulls (with bigger, heavier birds being considered hybrids, especially GWGU x HEGU) but this does not really seem to correspond with the reality on the breeding grounds…

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Long bill, flat head and snouty look:

The pulled out face, rather flat forehead, slightly elongated narrow bill and overall head and bill profile have been argued to give the bird a ‘snouty’ Herring Gull-like appearance unlike the idea many have of the Kumlien’s/Thayer’s group. But as stated by Kirk Zufelt, when he was asked to comment on the Danish gull, ’one of the biggest misconceptions in gull identification is the issue of structure in Thayer's Gull. Certainly lots of Thayer's have a rather petite rounded head and most of these are obviously females. Male Thayer's are on the other hand often robust and often more so than some Herrings especially the females. The flattish headed look is not infrequent in a robust male Thayer's’

In the following pages I have collected a series of long-billed individuals with an elongated ‘snouty’ appearance and rather flat forehead. Besides the obvious sexual dimorphism I do believe that apparent head shape can additionally vary according on posture and behavior as illustrated in the next slide with the Danish gull where the difference between the resting and the feeding bird is striking

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Herring Gull-like head shape:

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Herring Gull-like head shape:

California (Photo: Steve Hampton)http://www.tertial.us/gulls/thay1.htm

California (Photo: Steve Hampton)http://www.tertial.us/gulls/thay1.htm

Note the similar micro features:

-bill has long narrow nostrils-mandibles have convex cutting edges with obvious pale lip-gloss-upper mandible has a rather gentle curve to the tip-dark bill tip has identical rear end shape and the pale inner section has almost identical color shade-relatively large head with a full hind-neck

Note that the bill is relatively parallel edged with a small-to-moderate gonydeal expansion typical of the species

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England (Photo: Paul Hackett) http://birdingfrontiers.com/2012/04/07/thayers-gull-flight-shots/

Herring Gull-like head shape:

“The Lincolnshire bird”

Note the pale eye-ring, flat head, and long bill

England (Photo: Alan Lewis) http://www.surfbirds.com/gallery/search2.cgi?species=&photographer=&location=&county=Lincolnshire

England (Photo: Alan Tate) http://www.rarebirdalert.co.uk/v2/Content/weeklyreview2012no6.aspx?s_id=91176731

England (Photo: Steve Routledge) http://juncea.blogspot.dk/2012/04/mega-gull-and-msq-migrants.html

This THGU occurred in England less than two months after the Danish gull. How many THGU

can you find online matching this head- and bill shape?

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Herring Gull-like appearance:

Jared Clarke and Bruce Mactavish observed this THGU at the local landfill in St. John’s, Newfoundland

Initial impressions: When originally spotted, the gull was feeding amongst the garbage with American Herring, Glaucous and Great Black-backed Gulls. Structurally, this bird resembled Herring Gull in many aspects – including overall bulk, head and bill shape, and wing lengthhttp://birdtherock.files.wordpress.com/2013/03/thgu_2006.pdf

Adult Thayer’s Gull, St. John’s, NewfoundlandMarch 12th, 2006

Note flathead, andlong bill

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Kumlien’s Gull:

Kumlien's GullConnecticut (Photo: Keith Mueller)

Note the almost identical micro features and finer details:

-the bill has long narrow nostrils; the mandibles have convex cutting edges with obvious pale lip-gloss; the basal feathers protrude extensively on upper mandible; the upper mandible has a rather gentle curve to the tip; the dark bill tip has identical rear end shape and the pale inner section has almost identical color shade; the skull has a relatively long feathered area with concave shape in front of the eye; large eye with extensive eye-brow; relatively large head with a full hind-neck

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Long bill, flat head:

A study by Sutton & Parmelee, published in 1978, is interesting. They collected Thayer's Gull chicks at Victoria Island in the Canadian Arctic, and reared them in captivity to study the development of their plumages

Note the long bill and flat crown ofthe bird in the back

Victoria Island in the Canadian Arctic http://elibrary.unm.edu/sora/Wilson/v090n04/p0479-p0491.pdf

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http://gulldk.blogspot.dk/2012/07/danish-gull-versus-thayers-from-japan.html

Long bill, flat head and snouty look:

All from Choshi, Japan (Photo: Michiaki Ujihara)

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Ontario, Canada (Photo: Ron Howard) http://www.pbase.com/ronbirds/image/140163736

Long bill, flat head and snouty look:

Choshi, Japan (Photo: Michiaki Ujihara) http://www23.tok2.com/home/jgull/120228/th45_m.JPG

Birds that winter away from the US west coast, such as in Ontario, can also show a long bill and flat head (upper right) just like birds in Japan (below).

There are some obvious similarities between these two and the Danish one

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Long bill, flat head and snouty look:

Ireland (Photo: Paul & Andrea Kelly) http://www.irishbirdimages.com/pages/gallery/birdguide/birdguidepage_thayersgull.html

California (Photo: Chris Gibbins)http://chrisgibbins-gullsbirds.blogspot.dk/2011/03/some-1w-thayers-gulls-california.html

Note the similarities in proportions between these two (one from Ireland and one California) and the Danish gull

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California (Photo: Hans Larsson)http://www.talk.gull-research.org/download/file.php?id=3305&sid=fb9d2467f0ff6fa59dc559011d0f696f

Note the pale eye-ring, pale feathers around the bill, pale inner bill, barred axillaries, mottled underparts, irregular pattern on the greater coverts, and heavy structure

Long bill, flat head and snouty look: 29

Long bill, flat head:

Ontario, Canada (Photo: Brandon Holden) https://picasaweb.google.com/117329578255897846071/KumlienSThayerSGullsFromONTARIO#5577274471824210194

California (Photo: Peter Adriaens)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

Lake Michigan (Photo: Amar Ayyash)https://plus.google.com/photos/103465823166118508417/albums/5573275488535588785/5573279735334509378?banner=pwaI

Newfoundland (Photo: Dave Brown)http://birdingnewfoundland.blogspot.se/2011/12/2nd-winter-thayers-gull.html

Note the pale eye-ring

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Long bill, flat head: http://naturescapeimages.wordpress.com/2011/01/25/kumliens-gulls/thayersup/Connecticut (Photo: Julian Hugh)

British Columbia (Photo: Dave Ingram)http://islandnature.ca/wp-content/uploads/2011/10/thayers_gull-560x352.jpg

Note the pale eye-ring, palefeathers around the bill, and heavy structure

Note the pale eye-ring, flat head, and long bill

England (Photo: Alan Lewis) http://www.surfbirds.com/gallery/search2.cgi?species=&photographer=&location=&county=Lincolnshire

Choshi, Japan (Photo: Michiaki Ujihara) http://www23.tok2.com/home/jgull/081227/032_m.jpg

Note pale feathers around the bill, heavy structure, and chequered upperparts

Snouty look when feeding

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Long bill, flat head:

Another example of a long, sloping foreheadand strong bill away from the US west coast:

Duluth-Superior (Photo: Karl Bardon)http://www.pbase.com/karlbardon/image/120880973

Note the pale eye-ring, pale feathers around the bill, and heavy structure

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Long bill, flat head:

Note the obvious pale inner bill, whitish feathers around the bill, mottled underparts, irregular pattern on the greater coverts, and heavy structure

Ontario, Canada (Photo: North Shore Nature) http://northshorenature.blogspot.dk/2010/03/thayers-gull-near-rossport.html 33

Long bill, flat head:

Duluth-Superior (Photo: Karl Bardon)http://www.pbase.com/karlbardon/image/141334134

Duluth-Superior (Photo: Karl Bardon)http://www.pbase.com/karlbardon/image/140881548

Duluth-Superior (Photo: Karl Bardon)http://www.pbase.com/karlbardon/image/131906524

Duluth-Superior (Photo: Karl Bardon)http://www.pbase.com/karlbardon/image/141001307

Note the pale eye-ring, flat head, and long bill

Note the flat head, and long bill even in near-adults and adults

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Structure and body size:

It is not only due to the telephoto lens effect, but the Glaucous Gull behind the discussed gull was of average size and obvious much larger in overall size compared to the Danish gull. In comparison with Herring Gulls the Danish gull was judged to be within their smaller size and jizz range, thus being a smaller and slimmer type of Herring Gull

Glaucous Gull

Great Black-backed Gull

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Structure and body size:

Kirk Zufelt has written two blog posts on size variation in Thayer's Gull based on experiences from eastern Lake Superior in Ontario (see the posts for several great photos):

Part 1: http://larusology.blogspot.dk/2010/01/does-size-matter-part-1.htmlPart 2: http://larusology.blogspot.dk/2010/03/does-size-matter-thayers-gull-part-2.html

He says that: ‘Thayer's Gull is thought of by many as a relatively finely structured gull with a rounder head and finer bill than the Herring. Indeed the females are usually structured in this fashion. This however is not a diagnostic field mark at all. The male Thayer's can be quite robust and to my eye are near indistinguishable from the Herring Gull by structure. In fact many male Thayer's are much more robust and "Herring Gull-like" in structure than the female Herrings. The bottom line is the structure is a good way to narrow down the field but it is far from diagnostic’

He also says: ‘that one of the biggest misconceptions in gull identification is the issue of structure in Thayer's Gull. Certainly lots of Thayer's have a rather petite rounded head and most of these are obviously females. Male Thayer's are on the other hand often robust and often more so than some Herrings especially the Herring females’

I have also blogged about sexual dimorphisms: http://gulldk.blogspot.dk/2013/01/sexual-size-dimorphism-in-thayers-gull.html

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Structure and body size:

When evaluating the measurements in ’Gulls of North America, Europe and Asia’ by Olsen & Larsson a high degree of size variation among the larger species becomes apparent. There is significant variation between species, but also within and between sexes of the same species. The following measures represent the extreme values from skinned adult birds of both male and female:

Wing Bill WeightGreat Black-backed Gull 445-520 mm 53.9-66.7 mm 732-2275 gGlaucous-winged Gull 392-480 mm 46.4-64.3 mm 820-1690 gGlaucous Gull ssp. hyperboreus 408-501 mm 50.2-69.1 mm 964-2215 gGlaucous Gull ssp. barrovianus 414-484 mm 49.0-65.5 mm -Glaucous Gull ssp. pallidissimus 436-472 mm 56.3-70.0 mm -Iceland Gull 379-443 mm 36.3-53.5 mm 480-1039 gKumlien's Gull 380-442 mm 38.8-50.6 mm 530-970 gThayer’s Gull 384-442 mm 44.0-55.5 mm 712-1002 gAmerican Herring Gull 412-468 mm 44.2-62.1 mm 600-1650 gEuropean Herring Gull ssp. argentatus 385-480 mm 43.9-65.2 mm 717-1525 gEuropean Herring Gull ssp. argenteus 381-460 mm 44.4-63.9 mm 600-1150 gSlaty-backed Gull 406-479 mm 48.4-64.6 mm -Lesser Black-backed Gull ssp. graellsii 383-456 mm 45.5-57.2 mm 620-1100 g

It is obvious that Thayer’s Gull overlap with most of the larger gull species in the list and even significantly so with the five medium sized species such as American Herring Gull, European Herring Gull, Lesser Black-backed Gull, Kumlien's Gull and Iceland Gull. The weight of female Thayer’s is higher than that of male Kumlien’s which supports the more robust structure in Thayer’s

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Structure and body size:

Standard measures for adults from ‘Gulls of the Americas‘ by Howell & Dunn with sexes combined. Note the obvious overlap (often extensive) in most characters among similar species

Wing Bill TarsusGreat Black-backed Gull 442-511 mm 54.0-71.7 mm 67-84 mmGlaucous-winged Gull 390-455 mm 48.7-63.8 mm 60-75 mmGlaucous Gull (subspecies combined) 417-494 mm 48.6-70.0 mm 61-80 mmIceland Gull 379-435 mm 36.7-49.6 mm 50-65 mmKumlien's Gull 382-431 mm 38.5-50.1 mm 51-65 mmThayer’s Gull 380-439 mm 42.6-55.2 mm 53-68 mmAmerican Herring Gull 396-458 mm 46.1-61.5 mm 56-73 mmSlaty-backed Gull 402-465 mm 49.4-61.3 mm 60-75 mmLesser Black-backed Gull ssp. graellsii 380-446 mm 45.0-57.9 mm 54-69 mm

Zimmer wrote in 1990 (in ‘The Thayer's Gull Complex’, Pp. 114-130 in ‘A Field Guide to Advanced Birding’ by Kenn Kaufman): ‘I believe that our ideas regarding what a 'classic' Thayer's Gull should look like (structurally) are based primarily on the appearance of female Thayer's. Females of most large gulls differ from males of their own species in being smaller-bodied, with smaller, more rounded heads and shorter, thinner bill (...) With Thayer's and Herrings, intersexual differences can be dramatic’

This bias can temper our analysis of birds in the field and on photos

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Note the impressive head and bill, but also its apparently large size compared to the two Herring Gulls

Adult Thayer's Gull male, Danish Thule and Ellesmere Land Expedition 1939-40.Specimen found at Zoological Museum Copenhagen (Photo: Kent Olsen)

http://gulldk.blogspot.dk/2013/01/sexual-size-dimorphism-in-thayers-gull.html

Thayer's from the Danish Thule and Ellesmere Land Expedition:

THGU

THGU

THGU

HEGUHEGU

HEGU

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The Danish gull versus an accepted Thayer's from Connecticut:

http://sphotos-c.ak.fbcdn.net/hphotos-ak-ash3/734487_10151359817309480_2063489380_n.jpg

Connecticut (Photo: Patric Comins)Size compared with Great Black-backed Gull

Note the apparent large size of the Thayer’s Gull

Note the similarities in body shape and apparent size

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Proportions and body size:

Two examples of somewhat big, smithsonianus-like Thayer's Gulls from California, late January 2011

More photos of the two individuals at: https://picasaweb.google.com/115659792470435170210/1cThayerSGull#

California (Photo: Peter Adriaens)

California (Photo: Peter Adriaens)

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Proportions and body size:

Adult Glaucous-winged and Thayer's Gull. Tukwila, Washington. 30 December 2011. Photo: Amar Ayyash

Note large size of the Thayer’s Gull

in direct comparison to a

Glaucous-winged Gull

Michigan City, Indiana (Photo: Amar Ayyash)https://plus.google.com/photos/103465823166118508417/albums/5835663413890824817/5835661878006452146?banner=pwa

Michigan City, Indiana (Photo: Amar Ayyash)https://plus.google.com/photos/103465823166118508417/albums/5835663413890824817/5835661878006452146?banner=pwa

Note the large head, pale primaries, chequered upperparts and wing

coverts

Note the large head, pale primaries, chequered upperparts and wing coverts

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Proportions and body size:

First winter Thayer's and Glaucous-winged Gull, California. 30 December 2011. Photo: Amar Ayyash

Note large size of the Thayer’s Gull (in front) in direct comparison to a same aged Glaucous-winged Gull

Note the large head, pale primaries, chequered upperparts and wing coverts

Structurally, this bird resembled Herring Gull in many aspects – including overall bulk, head and bill shape, and wing length

Scan from ‘Gulls of Europe, Asia and North America’ by Olsen & Larsson

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Two-toned bill:

Some state that the two-toned bill isn't a good fit for Thayer's by February, but there has been posted photos of several Californian individuals in fresh dark plumage and with similar pale bill colour photographed as early as December:

December, California (Photo: Hans Larsson)http://www.talk.gull-research.org/download/file.php?id=3305&sid=fb9d2467f0ff6fa59dc559011d0f696f

Note the pale eye-ring, pale feathers around the bill, flat sloping forehead, barred axillaries, marbled underparts, irregular pattern on the greater coverts, and heavy structure

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Two-toned bill:

27 Jan 2011, California (Photo: Peter Adriaens)More photos of this individual at: https://picasaweb.google.com/115659792470435170210/1cThayerSGull#

Note the pale feathers around the bill, flat sloping forehead, marbled

underparts, and very heavy structure

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Two-toned bill:

This gull spent a day on the ice of Lake Superior in Thunder Bay, Ontario, CA on March 10, 2010

Note the pale inner bill, whitish feathers around the bill, mottled underparts, irregular pattern on the greater coverts, and heavy structure

10 March 2010, Ontario, Canada (Photo: North Shore Nature) http://www.flickr.com/photos/28113115@N00/4424157221/ 46

Two-toned bill:

27 January 2011, California (Photo: Peter Adriaens)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

31 January 2008, British Colombia (Photo: Guy Monty)http://www.flickr.com/photos/guylmonty/2233586953/sizes/z/in/set-72057594118619310/

28 December 2012, Niagar River (Photo: Amar Ayyash)https://picasaweb.google.com/lh/photo/TIcyBqXfkz4bNis0lYBHE2ZsMSMoNgltp9VFhGfvPTE?feat=directlink

Note this juvenile Thayer's with the bill base beginning to pale by late December

4 February 2012, Denmark (Photo: Kent Olsen)

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Pale orbital spot:

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Pale eye-ring:

The pale eye-ring has been discussed, but again that character is seen in other Thayer’s and its appearance change with posture and light situation

The pale eye-ring is less obvious and the eye itself appear smaller when the bird is resting and seen up against the light, i.e. completely matching numerous Thayer’s Gulls in the following photos

Great Black-backed Gull

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Pale eye-ring:

The pale eye-ring is also seen in other Thayer’s

Lake Michigan (Photo: Amar Ayyash)https://plus.google.com/photos/103465823166118508417/albums/5575613945291610945/5575613951310325522?banner=pwa

California (Photo: Peter Adriaens)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

California (Photo: Peter Adriaens)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

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Ontario, Canada (Photo: Kirk Zufelt)http://larusology.blogspot.dk/2010/03/does-size-matter-thayers-gull-part-2.html

Ontario, Canada (Photo: Peeter Musta)http://mustap.smugmug.com/Nature/Birding-in-Ontario/WaterlooDump/11045791_NVtdpr#!i=1739629361&k=Qczf8NL&lb=1&s=A

Ireland (Photo: Dermot Breen)http://uk400clubrarebirdalert.blogspot.dk/2010/01/apparent-thayers-gull-in-county-galway.html

British Colombia (Photo: Guy Monty)http://www.flickr.com/photos/guylmonty/2233586953/sizes/z/in/set-72057594118619310/

Pale eye-ring:

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Pale eye-ring:

California (Photo: Hans Larsson)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

California (Photo: Peter Adriaens) http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

Minnesota (Photo: Karl Bardon)http://www.pbase.com/karlbardon/image/107019541

California (Photo: Peter Adriaens)http://www.talk.gull-research.org/viewtopic.php?f=13&t=753

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Mottled underparts and barred axillaries:

The mottled underparts and barred axillaries have also been discussed, but again these character are also seen in other Thayer’s as illustrated in the following photos

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Mottled underparts and barred axillaries:

California (Photo: Peter Adriaens)http://www.talk.gull-research.org/viewtopic.php?f=13&t=753

http://www.talk.gull-research.org/viewtopic.php?f=13&t=753California (Photo: Peter Adriaens)

California (Photo: Peter Adriaens)http://www.talk.gull-research.org/viewtopic.php?f=13&t=753

California (Photo: Peter Adriaens)http://www.talk.gull-research.org/viewtopic.php?f=13&t=753

Some state that the axillaries are to obviously barred for THGU

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Mottled underparts and barred axillaries:

Some state that the axillaries areto obviously barred in the Danish gull, but compare with this Thayer’s

California (Photo: Peter Adriaens)http://www.talk.gull-research.org/viewtopic.php?f=13&t=753

Note the pale feathers around the bill,flat forehead, mottled underparts,heavy structure

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Primaries with little white at the tips:

People argue that that the primaries should be darker than tertials and they should have white crescents at their very tips, but as illustrated in this close-up, the primaries are actually darker than the tertials and they do also have white tips

However, these characters are highly variable within Thayer’s Gull as is illustrate in the following pages

White primary tip

Primaries are darker than the tertials

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Primaries with little white at the tips:

Here are 2 juvenile Thayer’s Gulls. The primaries are still growing, so its fair to assume that they were collected very near to where they hatched. They are from Igloolik in the core range of Thayer’s Gull in the northwest corner of Foxe Basin, Nunavut, Canada

Both birds look basically very similar and like juvenile Thayer’s Gulls, but one has obviously paler primaries than the other

The one with the darkest primaries also has very little pale edging to the outer primaries compared to the other

Nunavut, Canada (Photo: Martin Garner) http://birdingfrontiers.com/2012/03/24/juvenile-thayers-gulls-from-breeding-grounds/ 57

Primaries with little white at the tips:

Minnesota (Photo: Erik Bruhnke)http://www.pbase.com/image/140744501

Minnesota (Photo: Erik Bruhnke)http://www.pbase.com/birdfedr/image/119465454

http://www.tertial.us/gulls/thay1.htmCalifornia (Photo: Matt Brady)

California (Photo: Hans Larsson)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

Note the cold plumage tones, flat forehead, 'busy' covert pattern, and rather pale bill

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Primaries with little white at the tips:

Washington (Photo: Ryan Shaw) 10/15/2011http://www.flickr.com/photos/shyalbatross/6255883337/

Ireland (Photo: Dermort Breen)http://uk400clubrarebirdalert.blogspot.dk/2010/01/apparent-thayers-gull-in-county-galway.html

Note cold plumage tones, chequered wing and upperpart coverts, primaries only little darker than tertials, identical primary projection with equal spacing between tips, and already rather pale inner bill by October

http://larusology.blogspot.dk/2010/03/does-size-matter-thayers-gull-part-2.htmlOntario, Canada (Photo: Kirk Zufelt)

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Note the almost identical primary projections and evenidentical spacingbetween primarytips

Primaries with little white at the tips:

Niagar River (Photo: Amar Ayyash)https://picasaweb.google.com/lh/photo/TIcyBqXfkz4bNis0lYBHE2ZsMSMoNgltp9VFhGfvPTE?feat=directlink

Note this juvenile Thayer's with the bill base beginning to pale already in late December

Virginia Lake, Nevada (Photo: Martin Meyers)http://birdbum2.home.mindspring.com/Nevada/Thayers%20Gull%209a%20Reno%2011-8-07.jpg

Oregon (Photo: John Rakestraw)http://johnrakestraw.files.wordpress.com/2011/02/thayers-gull-first-cycle.jpg

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Primaries with darker subterminal spot:

The dark outer primaries become a little darker at the very tip and thus show a pattern not dissimilar to Glaucous Gull, Iceland Gull and Kumlien´s Gull. One could argue that this feature could indicate a hybrid origin. However, the characters is variable within Thayer’s Gull as illustrate with the two juveniles from Nunavat where one has spots similar to the Danish gull and the other one lacks them

Dark subterminal spot

Nunavut, Canada (Photo: Martin Garner) http://birdingfrontiers.com/2012/03/24/juvenile-thayers-gulls-from-breeding-grounds/

Dark subterminal spot

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Choshi, Japan (Photo: Michiaki Ujihara) http://gulldk.blogspot.dk/2012/07/danish-gull-versus-thayers-from-japan.html

Ontario, Canada (Photo: Brandon Holden) https://picasaweb.google.com/117329578255897846071/KumlienSThayerSGullsFromONTARIO#5577274471824210194

Relatively long legs:

California (Photo: Peter Adriaens)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

Choshi, Japan (Photo: Michiaki Ujihara) http://gulldk.blogspot.dk/2012/07/danish-gull-versus-thayers-from-japan.html

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Secondary skirt:

The row of feathers drooping below the greater coverts is called a secondary skirt and it is normally associated with large broad winged gull with long secondaries such as Glaucous-winged Gull

It has been argued that when a skirt is present in the smaller gull species it could indicate a hybrid origin. However, as the following pages illustrate a short secondary skirt as seen in the Danish gull can also be seen in other Thayer’s Gulls, but more importantly, the character is also occasionally present in species such as Kumlien’s Gull and Iceland Gull

The juvenile Thayer's Gull on the left in plate 36.8 in ‘Gulls of the Americas‘ by Howell & Dunn shows a complete secondary skirt. This bird was photographed at Whitehorse, Yukon Territory, in early October 2003

secondary skirt

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Secondary skirt:

The bird in Denmark back in 2002 showed a similar secondary skirt when standing and was accepted as the first TH for Denmark by the Danish rarities committee

Denmark (Photo: Morten Bentzon Hansen)http://www.netfugl.dk/pictures.php?id=showpicture&picture_id=233

Denmark (Photo: Morten Bentzon Hansen)http://www.netfugl.dk/pictures.php?id=showpicture&picture_id=235 64

secondary skirt

secondary skirt

secondary skirt

Note the almost identical pattern on scapulars and mantle in the two individual.

Note how at some angles there appears to be at least a strong onset of secondary skirt in this Norwegian bird from 2000 which was accepted as Thayer's Gullby the Norwegian rarities committee

http://cyberbirding.uib.no/gull/tg/juv_01.phpNorway (Photo: Alf Tore Mjøs)

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Secondary skirt is also something that justvaries with posture

http://johnrakestraw.net/2011/02/07/thayers-and-herring-gulls/Oregon (Photo: John Rakestraw)

http://www.ofo.ca/photoalbums/checklist/Gulls_Terns_Skimmers/Thayer%27s%20Gull/slides/thayersgulljuvkz.htmlOntario, Canada (Photo: Kirk Zufelt)

http://www.talk.gull-research.org/download/file.php?id=3304&sid=d7613058f695ab2316156b1a65967b18California (Photo: Hans Larsson)

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Newfoundland (Photo: Bruce Mactavish)http://gull-research.org/glaucoides/glauc3cy/c2yellow.html

Another thing is that a prominent secondary skirt is often shown by a quite similar looking taxon, namely Kumlien's Gull. Here a color-banded example from Newfoundland:

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Scotland (Photo: Chris Gibbins)http://gull-research.org/glaucoides/glauc3cy/3cyjang064.html

It can also be really prominent in Iceland Gull (glaucoides):

Presence or absence of a secondary skirt is also affected by stance/posture in gulls, making this character somewhat difficult to interpret at times.

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Tail and rump:

69

Tail and rump:

There is an almost complete match in rump and outer tail pattern between the Danish gull and other thayeri

Ontario, Canada (Photo: Brandon Holden) http://gulldk.blogspot.dk/2012/04/danish-gull-versus-thayers-from-ontario.html

California (Photo: Charlie Moores)http://www.talking-naturally.co.uk/thayers-gull-california/

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Moult timing and hybrids:

The Danish gull has a perfect moult stage for Thayer’s and as suspended moult is considered classic for the species it strongly supports the ID. All hybrids claimed to be similar to THGU in appearance shift their mantel and scapulars much earlier than thayeri. THGU hold off on the moult until the spring and during winter they only initiate the upperpart moult with the lower scapulars as mimicked in the Danish gull. The amount of missing lower scapulars in the Danish gull is found to identical to most first winter THGUs in February

Lower scapulars have been shed

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American Herring Gull x Glaucous Gull = Nelson’s Gull:

72Ontario, Canada (Photo: Kirk Zufelt)http://larusology.blogspot.dk/2009/11/nelsons-gull.html

Ontario, Canada (Photo: Kirk Zufelt)http://larusology.blogspot.dk/2009/11/nelsons-gull.html

The Nelson’s Gulls photographed in various parts of North America do not really look like the Danish gull

Even though there are similarities between the Danish bird and the hybrid in the photos here e.g. there are also some clear differences, not just in size and shape or bill pattern, but also in plumage.

Note e.g. that there are subtle differences in the pattern of tertials, shape of the lower scapulars

American Herring Gull x Glaucous Gull = Nelson’s Gull:

... but the most obvious differences between the Danish bird and the hybrid in the photos here are:

1) Bright pink bill, quite like Glaucous Gull (clearly duller in the Danish bird)

2) Short primary projection, again like Glaucous Gull. Note the difference in primary

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spacing in the composite with the Danish bird and the Nelson's Gull

3) Primary pattern. In the Danish bird, P6-10 have dark outer webs, and P4-5 have distinct dark subterminal spots. In the Nelson's Gull, only P7-10 have dark outer webs, and only P5-6 have distinct dark subterminal spots

Ontario, Canada (Photo: Kirk Zufelt)http://larusology.blogspot.dk/2009/11/nelsons-gull.html

European Herring Gull x Glaucous Gull = Viking Gull:

The numerous Glaucous Gull x European Herring Gull hybrids and backcrosses in Iceland do not look like the Danish gull either

http://hjkoskinen.kuvat.fi/kuvat/Glaucous+X/1cy+Espoo/http://www.talk.gull-research.org/viewtopic.php?f=7&t=12http://cyberbirding.uib.no/gull/ind_ufo.phphttp://www.netfugl.dk/pictures.php?id=listpictures&species_id=970&page_nr=1http://www.pbase.com/hans_larsson/viking_type_gulls_sw_iceland__28243_2010https://notendur.hi.is/~yannk/hybrid.html

Iceland, December 2013(Photo: Yann Kolbeinsson)

Note that this hybrid has a rather dark bill, but nevertheless it is easy to see that it is a hybrid based on plumage

Iceland, December 2013(Photo: Yann Kolbeinsson)

Note the early moult of the mantle

Note the early moult of the mantle

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Glaucous-winged Gull x American Herring Gull hybrids:

Keep in mind that there have been no records of Glaucous-winged Gull x American Herring Gull in Europe, and very few (if any) in Japan, i.e. west coast hybrids are not at all likely on range

They can be Thayer's Gull-like but always larger and bulkier, often with paler bill base than THGU and clearly an early moult of the mantle.

Below are two examples of first cycle Glaucous-winged Gull x American Herring Gull hybrids. The one to the right is a very Thayer's Gull-like bird. But look at the moulted mantle, thickset structure, shorter winged look

California (Photo: Alvaro Jaramillo)http://sphotos-f.ak.fbcdn.net/hphotos-ak-prn1/13563_10151214434633520_1056305931_n.jpg

California (Photo: Alvaro Jaramillo)http://sphotos-f.ak.fbcdn.net/hphotos-ak-prn1/13563_10151214434633520_1056305931_n.jpg

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Note the early moult of the mantle

Note the early moult of the mantle

The Danish gull versus a Thayer's-Kumlien's intergrade from Madison, Connecticut:

http://sphotos-a.ak.fbcdn.net/hphotos-ak-ash4/485949_121184524735388_1974266294_n.jpgMadison, Connecticut, Feb. 21, 2013 (Photo: Keith Mueller) 76

The Danish gull versus a Thayer's from Ontario in Canada:Note the classic dark secondary bar, silvery-grey underside of the primaries, andsilvery-grey inner webs to outer primaries, identical upper rump and tail

Ontario, Canada (Photo: Brandon Holden) http://gulldk.blogspot.dk/2012/04/danish-gull-versus-thayers-from-ontario.html

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The Danish gull versus a Thayer's from Ontario in Canada: Ontario, Canada (Photo: Brandon Holden) http://gulldk.blogspot.dk/2012/04/danish-gull-versus-thayers-from-ontario.html

Note the silvery-grey underside of the

primaries, dark trailing edge to underside of outer primaries, and identical upper rump

and tail

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The Danish gull versus a Thayer's from California:

The pro-thayeri characters are: pale fringes to tips of outer primaries; obvious silvery-grey inner webs to outermost primaries creating the venetian blind-effect; distinct dark peppering on inner primaries; subterminal marks on inner primaries pale and almost translucent; secondaries with thin, dark subterminal ‘arrowhead’ mark; dark secondary bar, but the outer secondaries are pale greyish brown; greyish cast to tertial centres; silvery-grey underside of the primaries; dark trailing edge to underside of outer primaries

California (Photo: Peter Adriaens)http://gulldk.blogspot.dk/2012/04/danish-gull-now-versus-thayers-from.html

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The Danish gull versus other Thayer's from California: All from California (Photo: Peter Adriaens & Hans Larsson)http://gulldk.blogspot.dk/2012/04/thayers-gull-in-direct-comparison-with.html

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Newfoundland (Photo: Dave Brown)http://birdingnewfoundland.blogspot.dk/2011/12/2nd-winter-thayers-gull.html

California (Photo: Chris Gibbins)http://chrisgibbins-gullsbirds.blogspot.dk/2011/03/some-1w-thayers-gulls-california.html

Note the silvery-grey underside of the primaries, dark trailing edge to underside of outer primaries, and barred upper rump and dark brown tail

The Danish gull versus other Thayer's Gulls:

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http://www.talking-naturally.co.uk/thayers-gull-california/California (Photo: Charlie Moores)

California (Photo: Chris Gibbins)http://chrisgibbins-gullsbirds.blogspot.dk/2011/03/some-1w-thayers-gulls-california.html

California (Photo: Clay Kempf) http://www.pbase.com/ternvomitthief/thayers_gull_tutorial

Note the classic dark secondary bar, silvery-grey underside of the primaries, dark trailing edge to underside of outer primaries, silvery-grey inner webs to outer primaries, and identical barred upper rump and dark brown tail

The Danish gull versus other Thayer's Gulls:

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Photo: Paul Archerhttp://www.irbc.ie/assets/images/thayers2.jpg

Examples of accepted European records:

IRELAND

http://www.irbc.ie/announcements/announce28.php

Note that the first-winter from Cork Dump, Co. Cork, February 1990 had a pale eye-ring and mottled underparts

Photo: Killian Mullarneyhttp://www.irbc.ie/assets/images/thayer1.jpg

Note that the adult from Killybegs, Co. Donegal, February 1998 had relatively long bill, flat forehead and heavy JIZZ

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Examples of accepted European records:

NORWAY

January 2000: http://cyberbirding.uib.no/gull/tg/juv_01.php

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Examples of accepted European records:

DENMARK

February 2002: http://www.netfugl.dk/pictures.php?id=showpicture&picture_id=368

Note that this Danish individual has rather pale inner half on bill by February, chequered wing coverts, especially greater coverts, and only very thin pale tips to primaries

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Photo: Ole Kroghhttp://www.netfugl.dk/pictures.php?id=showpicture&picture_id=247

Photo: Morten Bentzon Hansenhttp://www.netfugl.dk/pictures.php?id=showpicture&picture_id=240

Photo: Kim Aaenhttp://cyberbirding.uib.no/gull/tg/juv_02c.jpg

Examples of accepted European records:

DENMARK

February 2002

Note that it could also show a flat forehead (above) and an obvious pale eye-ring (left and right)

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Perspective

Winter 2011-2012 has brought the biggest invasion of Kumlien's Gulls ever to Europe. I do not know how many were seen, but there must have been hundreds. It is perhaps not so surprising then that an unusual number of "Thayer's Gull candidates" were reported (and photographed) too: one in England (the Lincolnshire bird), one in Scotland (Argyll), two in Ireland, two in Iceland, and the Danish bird

Regards

Kent Olsen

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Online discussions about the Danish gull:

Gull Research Organisation:http://www.talk.gull-research.org/viewtopic.php?f=13&t=753

Netfugl:http://www.netfugl.dk/pictures.php?id=showpicture&picture_id=47573

ID Frontiers:http://old.nabble.com/Thayer's-Gull-in-Denmark--td33544948.html

Selected photo references:

Chris Gibbins – photos from California:http://chrisgibbins-gullsbirds.blogspot.dk/2011/11/kumliens-conundrum.html http://chrisgibbins-gullsbirds.blogspot.dk/2011/03/some-1w-thayers-gulls-california.htmlhttp://chrisgibbins-gullsbirds.blogspot.dk/2008/12/selection-of-1-cy-thayers-gull.html Peter Adriaens – photos from California:https://plus.google.com/photos/115659792470435170210/albums/5726456887174109345

Kirk Zufelt – photos from Ontario, Canada:http://larusology.blogspot.dk/2009/11/herring-vs-thayers.htmlhttp://larusology.blogspot.dk/2009/11/7-species-of-gulls-simultaneously-at.htmlhttp://larusology.blogspot.dk/2010/01/does-size-matter-part-1.html http://larusology.blogspot.dk/2010/03/comment-on-comments.htmlhttp://larusology.blogspot.dk/2010/03/does-size-matter-thayers-gull-part-2.html

Kent Olsen – photos of the Danish gull:http://gulldk.blogspot.dk/2012/04/thayers-mage-larus-thayeri-thayers-gull.html

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Selected photo references:

Karl Bardon – photos from the Duluth-Superior area:http://www.pbase.com/karlbardon/thgu20082009&page=all Fall/winter 2008-2009http://www.pbase.com/karlbardon/thayers_gull_non_adults&page=all Fall/winter 2009-2010http://www.pbase.com/karlbardon/duluthsuperior_gulls_20102011 Fall/winter 2010-2011http://www.pbase.com/karlbardon/thayers_gull_20112012 Fall/winter 2011-2012

Steve Hampton – Gull Identification Website:http://www.tertial.us/gulls/thay_d.htm

Martin Ried – Gull Index:http://www.martinreid.com/Gull%20website/thguinx.html

Clive Harris:http://harrisbirds.com/Thayers1.htm

Bill Hubick – Marylandhttp://www.billhubick.com/photos/birds/thayers_gull.php

Jeff Poklen:http://www.pbase.com/jpkln/thayers

Michiaki Ujihara – The Japanese Gull page:http://www23.tok2.com/home/jgull/gullidentifi_.htm#N

Masashi Shinjo – Gulls of Japan:http://seichoudoku.at.webry.info/theme/bacb341938.html

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Photos of some of the latest claims from IRELAND:

2005, Marts, Barnatra, Co Mayohttp://www.irishbirdimages.com/pages/gallery/birdguide/birdguidepage_thayersgull.html

2010, February, Ross Beach, Cleggan, Co Galway – note large bird with pale eye-ring, flat forehead and long billhttp://uk400clubrarebirdalert.blogspot.com/2010/01/apparent-thayers-gull-in-county-galway.htmlhttp://www.irishbirding.com/birds/web/Display/sighting/20225/Thayers_Gull.htmlhttp://www.irishbirding.com/birds/web/Display/sighting/20335/Thayers_Gull.htmlhttp://www.freewebs.com/canarybirder/ukirelandnrcontinent.htm – scroll down to the February 2012 birdshttp://uk400clubrarebirdalert.blogspot.com/2010/02/irish-tayers-gull-and-yorkshire-black.htmlhttp://debenestuary.webs.com/thayers.jpg – from: http://debenestuary.webs.com/mybestukeirebirds.htm

2011, February, Liscannor, Co Clarehttp://birdingfrontiers.com/2011/02/23/another-juv-thayers-in-ireland/

2011, February, Rossaveal, Co Galway – note two-coloured bill, pale feathers around the bill and mottled underpartshttp://birdingfrontiers.com/2011/02/20/thayers-like-gull-in-galway/http://birdingfrontiers.com/2011/02/20/thayers-on-the-deck/

2012, January, Killala Harbour, Co Mayohttp://murfswildlife.blogspot.com/2012/01/thayers-gull.html

2012, February, Enniskillen, Fermanag, N. Irelandhttp://nibirding.blogspot.com/2012/02/andrews-back.htmlhttp://birdingfrontiers.com/2012/02/02/looks-like-a-proper-thayers-gull/http://www.birdguides.com/species/species.asp?sp=061017

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Photos of claims from SCOTLAND:

2011, November, Dunstaffnage Bay, Argyll – note pale eye-ring, flat forehead and long billhttp://uk400clubrarebirdalert.blogspot.com/2011/11/putative-thayers-gull-in-argyll.htmlhttp://www.birdguides.com/species/species.asp?sp=061017http://uk400clubrarebirdalert.blogspot.dk/2011/11/more-shots-of-dunbeg-high-arctic-gull.htmlhttp://hebsbirding.wordpress.com/2012/02/29/that-dunbeg-gull-again-thumbs-up-for-thayers/

Photos of claims from BRITAIN:

2010, November, Essex – Bruce Mactavish says YES to this onehttp://www.birdersplayground.co.uk/Thayers%20Gull,%20Essex%20Nov%202010.htmlhttp://uk400clubrarebirdalert.blogspot.dk/2010/11/thayers-gull-response-from-newfoundland.html

2012, April, Elsham, Lincolnshire – Phil Pickering says NO, but Steven Mlodinow says YES to this one!http://www.birdguides.com/species/species.asp?sp=061017http://uk400clubrarebirdalert.blogspot.com/2012/04/north-lincolnshire-thayers-gull.htmlhttp://uk400clubrarebirdalert.blogspot.com/2010/11/thayers-gull-response-from-newfoundland.htmlhttp://birdingfrontiers.com/2012/04/07/thayers-gull-flight-shots/http://birdingfrontiers.com/2012/04/06/dark-juvenile-thayers-gull/

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Thayer’s Gull in Denmark - supplementary materialHvide Sande HarbourFebruary 4, 2012

93A fairly typical juvenile Thayer's Gull photographed at the Recology Plant, Stanislaus

County, CA, 12 December 2011 (Photo: Oscar Johnson)http://www.flickr.com/photos/henicorhina/sets/72157628353003471/

Note the pale eye-ring, pale feathers around the bill, inner bill becoming pale by December, and note heavy structure and rather bulbous bill

The Danish gull versus accepted Thayer's

94Ontario, Canada (Photo: Kirk Zufelt) http://gull-research.org/thayers/images/kirk/tgprimlarus1855.jpg

Note flat head, long and heavy bill,and note heavy structure

The Danish gull versus accepted Thayer's

95JC Dump, Jefferson Co, WI 18 November 2013

(Photo: Cynthia Bridges)http://www.flickr.com/photos/76901502@N03/10936840486/

Note the pale eye-ring, pale feathers around the bill, inner bill becoming pale by December, and note heavy structure

Note the pale eye-ring, pale feathers around the bill, inner bill becoming pale by November, and similar upperparts

The Danish gull versus accepted Thayer's

96Ontario, Canada (Photo: Kirk Zufelt) http://gull-research.org/thayers/images/kirk/tkgssm2505.jpg

Note the pale eye-ring, pale feathers around the bill, heavy structure, mottled underparts,

and rather pale primaries

The Danish gull versus accepted Thayer's

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Ontario, Canada (Photo: Kirk Zufelt) http://gull-research.org/thayers/images/kirk/tkgssm2505.jpg

The Danish gull versus accepted Thayer's

98October 27 2013, Chicago, IL. (Photo: Amar Ayyash) http://gull-research.org/thayers/thayers1cy/1cyoct003.html

Note pale window on innerprimaries which continue to the

inner webs of the outer primaries.

Also note the lack of dark pigmentationon the inner web tips of P1-P4, with just a

bit of faint darker on P4.

The Danish gull versus accepted Thayer's

99November 05 2011, Chicago, IL. (Photo: Amar Ayyash) http://gull-research.org/thayers/thayers1cy/1cynov023.html

The Danish gull versus accepted Thayer's

100last week of November 2010, CA. (Photo: Hans Larsson) http://gull-research.org/thayers/thayers1cy/1cynov009.html

The Danish gull versus accepted Thayer's

101November 01 2009, Wisconsin Point, Superior, WI.

(Photo: Erik Bruhnke) http://gull-research.org/thayers/thayers1cy/1cynov017.html

The Danish gull versus accepted Thayer's

102February 20 2010, Winthrop Harbor, IL. (Photo: Erik Bruhnke) http://gull-research.org/thayers/thayers2cy/2cyfeb015.html

The Danish gull versus accepted Thayer's

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The Danish gull versus accepted Thayer's

November 05 2011, Chicago, IL. (Photo: Amar Ayyash) http://gull-research.org/thayers/thayers1cy/1cynov023.html

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The Danish gull versus accepted Thayer's

March 23 2011, Fernhill Wetlands, Forest Grove, Oregon (Photo: Greg Gillson) http://gull-research.org/thayers/thayers2cy/2cymar03.html

105January 6, 2014, Madison, Connecticut (Photo: Keith Mueller) https://www.facebook.com/media/set/?set=pcb.637639146282309&type=1

Large type Iceland Gull / Kumlien’s Gull

106January 6, 2014, Madison, Connecticut (Photo: Keith Mueller) https://www.facebook.com/media/set/?set=pcb.637639146282309&type=1

Large type Iceland Gull / Kumlien’s Gull

107January 6, 2014, Madison, Connecticut (Photo: Keith Mueller) https://www.facebook.com/media/set/?set=pcb.637639146282309&type=1

Large type Iceland Gull / Kumlien’s Gull

108January 6, 2014, Revere Beach, Massachusetts (Photo: Dorian Anderson) http://www.dorianandersonphotography.com/Revere-mystery-gull/i-T63Hk9V

Large type Kumlien’s Gull

109January 6, 2014, Revere Beach, Massachusetts (Photo: Dorian Anderson) http://www.dorianandersonphotography.com/Revere-mystery-gull/i-T63Hk9V

Large type Kumlien’s Gull

110January 6, 2014, Revere Beach, Massachusetts (Photo: Dorian Anderson) http://www.dorianandersonphotography.com/Revere-mystery-gull/i-T63Hk9V

Large type Kumlien’s Gull

111January 6, 2014, Revere Beach, Massachusetts (Photo: Dorian Anderson) http://www.dorianandersonphotography.com/Revere-mystery-gull/i-T63Hk9V

Large type Kumlien’s Gull

112January 19, 2014, Essex, Great Britain (Photo: Richard Bonsers) https://www.facebook.com/media/set/?set=pcb.587336054674141&type=1

Viking Gull

Note the complete lack of a dark secondary bar

113January 14, 2014, Norge (Photo: Sigmar Lode) http://artsobservasjoner.no/artportalen/gallery/Image.aspx?rappsyst=1&obsid=12797170&imageID=385565

Viking Gull

Note the complete lack of a dark secondary bar and lack of dark trailing edge on the outer primaries

114January 19, 2014, Essex, Great Britain (Photo: Richard Bonsers) https://www.facebook.com/media/set/?set=pcb.587336054674141&type=1

Viking Gull

Note the complete lack of a dark secondary bar and lack of dark trailing edge on the outer primaries

Body size: People argue that the lack of precise info on body size causes some concern

In direct comparison the Danish gull had a size and JIZZ similar to a small and slim European Herring Gull and was thus clearly within the range of THGU

Even though this impression is only documentedby personal observation, this photo certainlysupports that impression

It is thus not only due to an effect of thetelephoto lens that the Glaucous Gulland the Great Black-backed Gullboth seem very muchLarger than theDanish gull

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Glaucous Gull

Great Black-backed Gull

116

Head shape and bill length

People still argue that both head shape and bill length causes some concerns

When photographing a 2cy Iceland Gull in Denmark in April I again noticed how head shape and facial expression can change according to posture

In order to illustrate the similarities in shape, appearance and facial expression, I have cropped the head of both the Danish gull and the Iceland Gull from Denmark in the following slides

Note how the Iceland Gull actually has a more robust bill with a more pronounced gonys-angle and bulbous upper mandible

The Danish gull versus Iceland Gull

2cy Iceland Gull , 17 April 2014, Skagen Harbour, Denmark (Photo: Kent Olsen)http://gulldk.blogspot.dk/2014/04/iceland-gull-larus-glaucoides-2cy.html

Note how the head shape in the following cropped photos of the Iceland Gull vary depending on posture and behavior

2cy Iceland Gull , 17 April 2014, Skagen Harbour, Denmark (Photo: Kent Olsen)http://gulldk.blogspot.dk/2014/04/iceland-gull-larus-glaucoides-2cy.html

Note how the head shape in the cropped photos below varies depending on posture and behavior

The Danish gull versus Iceland Gull

Note the flat forehead and crown

Note the flat forehead and crown

2cy Iceland Gull , 17 April 2014, Skagen Harbour, Denmark (Photo: Kent Olsen)http://gulldk.blogspot.dk/2014/04/iceland-gull-larus-glaucoides-2cy.html

The Danish gull versus Iceland Gull Note how the head shape in the cropped photos below varies depending on posture and behavior

2cy Iceland Gull , 17 April 2014, Skagen Harbour, Denmark (Photo: Kent Olsen)http://gulldk.blogspot.dk/2014/04/iceland-gull-larus-glaucoides-2cy.html

The Danish gull versus Iceland Gull

Note the similar micro features:-mandibles have convex cutting edges with obvious pale lip-gloss-upper mandible has a rather gentle curve to the tip-relatively large head with a full hind-neck

Note how the head shape in the cropped photos below varies depending on posture and behavior

Latest news from Gull Research Organization

Thayer's Gull has been added to the ORG pages and the material includes a great number of individuals from each age classes and as such represents a valuable reference. The people compiling the material have chosen to include the Danish gull as seen here:

Gull Research Organization http://gull-research.org/thayers/thayers2cy/2cyjan43denmark.html

Latest news from Gull Research Organization

Gull Research Organization http://gull-research.org/thayers/2cyjan.html

Thayer's Gull has been added to the ORG pages and the material includes the Danish gull as seen here:

Latest news from Hans Larsson