glaucoides - kumlieni

(last update: February 16, 2022)

Kumlien's Gull (kumlieni) 1st cycle - 6th cycle, 2022, Julianadorp, the Netherlands.

Some thoughts on the returning Julianadorp kumlieni and comparison with both glaucoides and kumlieni in same age-classes.
This particular bird has been returning (and, currently, February 2022 still does) to the village of Julianadorp, the Netherlands for six winters in a row.
Its habits and look-out posts in the village (together with the status of Iceland Gulls in the Netherlands) convincingly confirmed it's the same bird throughout the years,
and this allows us to analyze the plumage development for this individual.
First two years everyone considered this to be a 'normal glaucoides', and after some years with Iceland Gull influxes, it was only visited by few birders, mainly from the region.
Then it came as a great surprise to see the 4th cycle bird back with faint but obvious patterned outer primaries, indicating this could be kumlieni.
In the two following winters, the adult plumage confirmed suspicions: the pattern remained, and we are dealing with a Kumlien's Gull kumlieni.
Now how would this affect our look at what we consider 'normal 1st cycle glaucoides'? What are the odds such birds turn into kumlien's Gulls?

- Henk Post, Leon Edelaar & Mars Muusse -

Observations:

The webpage below compares the Julianadorp Kumlien's Gull (centre) with Kumlien's Gulls from St. John's, Newfoundland (left) and with Iceland Gulls from Europe (right).
Comparisons of both standing and flying birds in the same age-class (we use 'cycles', though European birders probably prefer 'winters', which corresponds more or less for birds from the Iceland Gull complex).
The current view, and that is what we adopt here too, is that adult birds with immaculate white primary tips are regarded glaucoides, and birds with pigmented primaries categorised as kumlieni.
This leaves a very clear division, with bulk of the birds easily classified and only few problem birds. A few of such problem birds are mentioned here on this page as well.
We added comments by Dave Brown and Lancy Cheng, who both live in St. John's, Newfoundland, and who may study kumlieni daily in what should be regarded as 'the major wintering site for this taxon'.
A full set of images of the Julianadorp bird can be found at THIS PAGE (50+ images).

Kumlien's Gull (kumlieni) 1st cycle in Newfoundland

Kumlien's Gull (kumlieni) 1st cycle - Julianadorp, the Netherlands

Iceland Gull (glaucoides) 1st cycle in Europe

Iceland Gull (glaucoides) 1st cycle, November 27 2010, Peterhead, Schotland. Picture: Chris Gibbins.
Note bi-coloured bill in November, and dark diamond shapes (or 'arrow head shapes') at tips of outer primaries. In folded wing, 1st cycle glaucoides show white outerwebs of primaries.

Kumlien's Gull (kumlieni) 1st cycle, January 29 2013, St John's, Newfoundland, Canada. Pictures: Peter Adriaens. Pale bird within 'kumlieni wintering grounds', inseparable from glaucoides.

See another paler 1st cycle kumlieni in flight (February 04 2013, St John's. Pictures: Peter Adriaens), which is pale overall, but shows outer primary patches darker than inner primaries.

Kumlien's Gull (kumlieni) 1st cycle (2CY), March 26 2017, Julianadorp, the Netherlands. Picture: Henk Post.

Inseparable from glaucoides. Still no obvious pale bill base by late March (pro kumlieni). Folded wing with immaculate white primaries (but remember original tone effected by bleaching in late winter). Transversal bars on tertials continue over the full width, also at proximal part.

Iceland Gull (glaucoides) 1st cycle, February 13 2018, Sligo, Ireland. Picture: Richard Bonser.
1st cycle glaucoides have white outerwebs on the outer primaries when the wing is folded.

Another very pale 1st cycle glaucoides with bi-coloured bill (December 12 2018, IJmuiden, the Netherlands. Picture: Mars Muusse).

Kumlien's Gull (kumlieni) 1st cycle, February 03 2013, St John's, Newfoundland, Canada. Pictures: Peter Adriaens.
Birds with the outer primaries this much darker than the inner ones should pose no ID problem. No diamond shapes at tips of outer primaries, rather plain coloured with darker shaft streak. Tail folded, but band seems pretty solid.

Iceland Gull (glaucoides) 1st cycle, January 24 2017, Scheveningen, the Netherlands. Picture: Mars Muusse. 1st cycle with 'Nearctic look' (dark tail, dense barring on undertail coverts, solid texture on neck and underparts), in darker end of the glaucoides spectrum. Note that even the darkest glaucoides still have white outerwebs on the folded wing.
From the same location, here is a coarsely marked bird (January 23 2017. Picture: Mars Muusse).

Iceland Gull (glaucoides) 1st cycle, March 06 2017, Katwijk, the Netherlands. Picture: Mars Muusse.
Classic bird showing all white outer primaries, pale centres on secondaries, and tail band broken up in multiple lines. In spring, white parts of feathers may be heavily worn.

Kumlien's Gull (kumlieni) 1st cycle (2CY), March 30 2017, Julianadorp, the Netherlands. Picture: Henk Post.

Iceland Gull (glaucoides) 1st cycle, January 27 2020, London, England. Picture: Jamie Partridge.
Another classic glaucoides in W Europe: no hint of dark patches on outer primaries.

Kumlien's Gull (kumlieni) 2nd cycle

Kumlien's Gull (kumlieni) 2nd cycle - Julianadorp, the Netherlands

Iceland Gull (glaucoides) 2nd cycle

Iceland Gull (glaucoides) 2nd cycle, January 04 2012, Stellendam, the Netherlands. Picture: Marcel Klootwijk. Classic glaucoides with already pale eye and almost completely white outer primaries.

Kumlien's Gull (kumlieni) 2nd cycle (3CY), January 20 2018, Julianadorp, the Netherlands. Picture: Henk Post.

Iceland Gull (glaucoides) 2nd cycle, February 12 2012, Peterhead, Schotland. Picture: Chris Gibbins.
Brown wash obvious on inner primaries, not on outer primaries.

Kumlien's Gull (kumlieni) 3rd cycle

Kumlien's Gull (kumlieni) 3rd cycle - Julianadorp, the Netherlands

Iceland Gull (glaucoides) 3rd cycle

"Iceland Gull' 3rd cycle (4CY), March 01 2010, Njardvik, SW Iceland. Picture: Hans Larsson.
Dark glaucoides or pale kumlieni? Outer primaries darker than inner primaries, but pattern not typical for kumlieni (no impression of "ghost mirror"), and primaries not obviously darker than primary coverts (hence, okay for glaucoides). Solid, contrasting tail advocates kumlieni. Pale iris better suits glaucoides.

Kumlien's Gull (kumlieni) 4th cycle

Kumlien's Gull (kumlieni) 4th cycle - Julianadorp, the Netherlands

Iceland Gull (glaucoides) 4th cycle

Kumlien's Gull (kumlieni) 4th cycle (5CY), February 03 2020, Julianadorp, the Netherlands. Picture: Mars Muusse. Ghost mirrors on P9 and on P10.

Kumlien's Gull (kumlieni) L0 4th cycle (4CY), November 14 2017, Quidi Vidi Lake, St. John's, Newfoundland. Picture: Lancy Cheng.
As 1st cycle, L0 was a white-plumages individual, also on the outer primaries. This year's appearance is quite classic, with an obvious grey tone on outer primaries, being darker than the upperparts.

Kumlien's Gull (kumlieni) 4th cycle (5CY), February 03 2020, Julianadorp, the Netherlands. Picture: Mars Muusse.
Sub-terminal pigmentation (albeit faint) on P7-P10. Darker shaded outwerwebs also on P7-P10 which is obvuiously darker than any brown hue on primary coverts.

Kumlien's Gull (kumlieni) adult

Kumlien's Gull (kumlieni) adult - Julianadorp, the Netherlands

Iceland Gull (glaucoides) adult

Kumlien's Gull (kumlieni) H5 10th cycle, January 26 2021, St. John's. Picture: Lancy Cheng. H5 is a classic bird with average pigmentation.

For this particular webpage we now focus on the paler end of the kumlieni spectrum, as they most challenge glaucoides. Dave Brown, from St. John's Newfoundland, studied Kumlien's Gulls extensively. He summarized his observations in his excellent BLOG. Kumlieni differs from glaucoides in:
- primary coloration: kumlieni varies in dark marking on (sometimes 6) usually 4 outer primaries. palest birds have pure white wing tips with dark pigment restricted to the outer web of P10 (sometimes very faint). Adult glaucoides never has dark markings in the wings, hence always pure white tips and lacking any dark marbling in the outer web of P10.
- mantle shade: kumlieni is slightly paler than smithsonianus HERG, while glaucoides is as pale a Glaucous Gull or paler.
- iris color: kumlieni can vary from very pale to very dark, but always has at least some dark peppering in the iris, while glaucoides normally has a fully pale eye without dark peppering ranging pale to creamy yellow reminiscent of Glaucous Gull.
- structure: on average kumlieni seem to appear larger billed, with less rounded head, more menacing and bulky overall. The smallest glaucoides can appear very dainty with quite small, Dove-like heads.

Kumlien's Gull (kumlieni) 5th cycle (6CY), January 21 2021, Julianadorp, the Netherlands. Picture: Henk Post. As adult, it can now be scored using the Howell & Mactavish classification (Alula 1/2003).

In 2021 it is 5th cycle (6CY) and in 2022 6th cycle ( 7CY), lacking brown wash on primary coverts, which was still present in 2020.
Wingtip darkness score: 2 - medium grey (Estimated Kodak 7-10). In the study by Howell & Mactavish, about 77% of Kumlien's Gulls in New Foundland belong to this category, see Table 1.
Wingtip scoring for dark markings on P5-P10: 0-0-0-1-3-1 (very faint band on P7?). See Plate 1 for explanation.
Wingtip pattern category: Type D, Stage 2, darker grey marks on the outer three primaries with subterminal marks on one primary. See primary patterns for explanation. In the study by Howell & Mactavish, about 11% of Kumlien's Gulls in New Foundland belong to this category, see Table 2.
Iris colour variation: 3 - apparently unmarked pale yellow (like an adult Herring Gull but typically slightly darker yellow). In the study by Howell & Mactavish, about 19% of Kumlien's Gulls in New Foundland belong to this category, see Table 3. Classification on speckling: Class 1 - yellow iris, 0% > 1% speckling, see iris speckling).

Presumed Iceland Gull (glaucoides) adult, St. John's, Newfoundland. Picture: Dave Brown.
Illustrative for upperpart greytone. Compare to smithsonianus Herring Gull on left and Kumlien's Gulls on right and behind. Also note similarity in Kumlien's and Herring Gull mantle shade. Note this individual shows all four key features mentioned above by Dave (primary coloration, mantle shade, iris color & structure):
- pale mantle, obviously one shade paler than average kumlieni,
- pure, pale yellow eye, lacking dark peppering on the iris,
- pure white wingtips, with silvery grey bases which do not strongly contrast,
- Structurally this bird was a little bulky, so probably a male.

Kumlien's Gull (kumlieni) 5th cycle (6CY), January 21 2021, Julianadorp, the Netherlands. Picture: Henk Post. The pigmented outerwebs are even visible in the folded wing.

Iceland Gull (glaucoides) adult, February 12 2012, Peterhead, Schotland. Picture: Chris Gibbins. Classic bird with peppered iris. Here another adult glaucoides (January 31 2012, Texel, the Netherlands. Picture: Jos van den Berg).

Kumlien's Gull (kumlieni) 5th cycle (6CY), January 24 2021, Julianadorp, the Netherlands. Picture: Mars Muusse.

Kumlien's Gull (kumlieni) 6th cycle (7CY), February 15 2022, Julianadorp, the Netherlands. Picture: Mars Muusse.

Iceland Gull (glaucoides) adult, February 04 2017, Iceland. Picture: Yann Kolbeinsson.
When you zoom in, you will notice this individual has a peppered iris.

Another adult glaucoides in flight, photographed by Liam Singh in the heart of "kumlieni area", at St. John's. A nice pale-mantled bird.

Iceland Gull (glaucoides) adult, March 21 2005, Iceland. Picture: Yann Kolbeinsson.