Wednesday, 9 July 2014

The record influx of Kumlien’s Gulls in Denmark


The intention with this post is to provide some overview which can assist the Nordic Rarities Committees in their future assessment of kumlieni claims in Scandinavia.

A selection of individuals from the large influx of Kumlien's/Iceland Gull-types in Denmark during the winter 2011-2012 have been categorized into different groups below according to current identification criteria. Because there is still too much uncertainty about the variation in glaucoides, a rather conservative line has been applied.

Typical examples which Rarities Committees should accept

These individuals have all been identified as Kumlien’s Gulls based on their primary pattern. They have subtle dark shading on the outer webs of the outer primaries with the colour being darker on the outer than on the inner web. Moreover, the dark shading on P6-P9 reaches the primary tips where the dark colour penetrates onto the inner web and thus creates a back-curving hook which is considered to be a significant kumlieni character. The dark colour is often darkest at the very tip of the feather and half way out on the outer web. Some individuals also have a faint 'ghost mirror' on P10 and sub-terminal bands on the other outer primaries.

Note that the dark shading on the outer primaries of especially second winter individuals is darker than the shading on the primary coverts and the inner primaries. Additionally, the outer primaries are darker or at least not paler than the secondaries.

#1.1: 3cy, 13.1-26.2.2012, Hirtshals Harbour (Case: 2013-168) - kumlieni

#1.2: 4cy, 8.1-3.3.2012, Hanstholm Harbour (Case: 2013-34) - kumlieni

#1.3: 4cy, 9.1-5.3.2012, Hanstholm Harbour (Case: 2012-248) - kumlieni

#1.4: 4cy, 21.1-26.2.2012, Hirtshals Harbour (Case: 2013-35) - kumlieni

#1.5: 4cy+, 8.1.2012, Blåvandshuk, Blåvand (Case: 2013-85) - kumlieni

Problematic birds which are currently not without doubt

Identifications of these examples are not so straightforward. All of these individuals may be Kumlien’s Gulls; however, for several of them it does not seem safe to exclude well-marked Iceland Gulls and for some individuals the latter solution actually seems like the most plausible.

Most individuals have rather dark peppered eyes, light grey marbling on outer webs of outer primaries, some faint pigmentation along the tip of the outer primaries (sub-terminal bands) and some photos give the impression of a diluted version of a “string of pearls”.

However, it is important to note that it is not abnormal for 2nd- and, especially, 3rd-cycle glaucoides to show a brown wash on the outer primaries. The plumage of such well-marked immature gulls is known often to look quite retarded, with still lots of brown in the wing, and where the brown wash on the outer primaries of such birds simply matches the brown wash on outer secondaries, as is often the case in other 3rd-cycle gulls (e.g. Herring Gull). It could thus be considered just to be a trait of immature plumage rather than a clear indication of Kumlien’s Gull.

#2.1: 3cy, 23.1-3.3.2012, Thyborøn Harbour (Case: 2013-169) - kumlieni?

#2.2: 4cy, 11.1-19.2.2012, Hanstholm Harbour (Case: 2013-171) - kumlieni?

#2.3: 4cy, 13.1.2012, Blåvandshuk, Blåvand (Case: 2013-174) - kumlieni?

#2.4: 4cy, 15-16.1.2012, Blåvandshuk, Blåvand (Case: 2013-165) - kumlieni?

#2.5: 4cy, 28.1.2012, Thorsminde Harbour (Case: 2013-164) - kumlieni?

#2.6: 4cy, 3.2.2012, Aabenraa Harbour (Case: 2013-167 and 2013-163) - kumlieni?

#2.7: 4cy, 4.2.2012, Hvide Sande Harbour (Case: 2013-170) - kumlieni?

#2.8: 4cy, 5.2.2012, Hirtshals Harbour - kumlieni?

#2.9: 4cy+ 5.2.2012, Hirtshals Harbour - kumlieni?

#2.10: 4cy+, 5.2.2012, Hirtshals Harbour - kumlieni?

Iceland Gulls as a reference

These gulls which have all been recorded during the record influx of Kumlien’s Gulls are labeled as putative Iceland Gull instead of calling them definite Iceland Gulls. This line was followed because completely white-winged Kumlien’s Gull is claimed to be indistinguishable from glaucoides Iceland Gull.

#2.1: 3cy, 8.1.2012, Blåvandshuk, Blåvand - glaucoides

#2.2: 3cy, 10.1.2012, Hanstholm Slamdepot - glaucoides

#2.3: 3cy, 13-15.1.2012, Blåvandshuk, Blåvand (Case: 2013-175) - glaucoides

#2.4: 3cy, 14.1.2012, Blåvandshuk, Blåvand (Case: 2013-176) - glaucoides

#2.5: 3cy, 4.2.2012, Hvide Sande Harbour (Case: 2012-247) - glaucoides

#2.6: 3cy, 4.2.2012, Hvide Sande Harbour - glaucoides

#2.7: 3cy, 5.2.2012, Hanstholm Harbour - glaucoides

#2.8: 3cy, 5.2.2012, Hanstholm Harbour - glaucoides

#2.9: 3cy, 5.2.2012, Hanstholm Harbour - glaucoides

#2.10: 3cy, 5.2.2012, Roshage, Hanstholm - glaucoides

#2.11: 3cy, 5.2.2012, Hirtshals Harbour - glaucoides

#2.12: 4cy, 4.2.2012, Hvide Sande Harbour - glaucoides

#2.13: 4cy, 4.2.2012, Hvide Sande Harbour - glaucoides

#2.14: 5cy, 4.2.2012, Hvide Sande Harbour - glaucoides

#2.15: 5cy+, 5.2.2012, Hirtshals Harbour - glaucoides

For reference on some of the well describes primary patterns in Kumlien’s Gull please look at the excellent work by Howell and Mactavish (2003). One type which is missing is the one where the outer webs of the outer primaries are not obviously dark pigmented and approach the type A (stage 0) or somewhere between the type A (stage 0) and type B-C (stage 1) except for the presence of faint sub-terminal bands near the tip of at least p8-p9. Sometimes there is the impression of a faint “string of pearls” due to the pigmentation on inner primary webs reach further towards the tip than what I find typical for glaucoides. One could argue that such a primary pattern would fit in right with the type D-F (stage 2) with respect to the sub-terminal primary band, whereas the colouring of the outer webs would fit in between type A (stage 0) and type B-C (stage 1).

In these photos I have sampled individuals showing a primary pattern where slightly darker grey pigmentation can only be discerned on very close range or on high quality flight shots. Note that some individuals only have darker grey on the outer web of P10 whereas on other individuals there are only or additionally some darker grey markings visible at the distal end of the grey tongue on the inner web; i.e. the darker pigmentation runs as a more or less distinct line along the inner edge of grey basal portion of the feather. In the field such birds would most likely appear "white-winged" as the darker grey stripe or pigmentation is only noticeable at certain angles.

The question is whether having dark grey running along the grey tongue and without any dark on the outer web is within pure glaucoides Iceland Gull or if such individuals are in fact pale Kumlien’s Gulls. I believe the latter is the case, but when assign record in Rarities Committees a conservative line should be applied and such individuals should only be accepted if they are documented by high quality photos.


Howell, S.N.G. & Mactavish, B. 2003. Identification and variation of winter adult Kumlien's Gulls. Alula 9:2-15.

No comments: