Another Herring Gull (Larus argentatus) with yellowish legs

This European Herring Gull (Larus argentatus) was seen on January 3, 2015 at Havmølle Å on Djursland in Denmark. Note the yellowish legs, rather distinct primary pattern with much black, incomplete band on P5 and upperparts a little darken than on nearby argentatus (see video for color on upperparts).

Herring Gull (Larus argentatus) with much white in primaries

This Herring Gull was seen in Hanstholm Harbour on 30 December 2013. It has a primary pattern which reminds of what is seen in some birds labelled as hybrid hyperboreus x argentatus (Viking Gull), but as it lacks a clear influence from Glaucous Gull other than in the outer primaries, it is considered to be European Herring Gulls with reduced or aberrant pigmentation.

Note the distinct thayeri pattern on P9 on the adult-type Herring Gull in the front 

Herring Gull with a grey 'pseudo-mirror' on the underside of P9

A grey mirror found on the underside of P9 or P10 has been suggested as a supporting micro feature for distinguishing adult American Herring Gulls from European Herring Gulls. It is described as a somewhat isolated grey spot or grey hole inside the black pattern on the underside of P9 or P10. The grey spot is either completely surrounded by black or seen as a grey cut which is open towards the base of the feather. It may be present in both wings at the same time or only in one of the wings.

The feature is apparently rare in European Herring Gull, but has been seen in a few hybrids (or backcrosses) of Glaucous Gull x Herring Gull in Iceland. During Christmas holiday this year I looked through some more of my photos of apparent argentatus Herring Gulls, and came across the individual below which was seen on December 28, 2008 in Østerby Harbour on the island Læsø in Denmark. It represents the second European Herring Gull that I have ever documented with such a small grey ‘pseudo-mirror’. The first example was this one from the other end of the same island.

Another interesting character in this individual is that there is no mirror on P9. However, it is widely known that there is extensive variation in the primary pattern of European Herring Gull. We also know that precise pattern changes over years as documented by Maarten van Kleinwee

First winter argentatus Herring Gull with pink bill and black distal mark

There is a tendency for both smithsonianus and argentatus to develop a pale base to the bill quite early in their first winter, with the most extreme birds such as this which may approach first-year Glaucous Gull or California Gull in this respect. It was photographed on January 25, 2014 in Grenå Harbour on Djursland.

Herring Gull (Larus argentatus) with reduced pigmentation seen in Feldballe

Some of these pale type Herring Gulls can recall birds labelled as hybrid hyperboreus x argentatus (Viking Gull), but as this individual lacks a clear influence from Glaucous Gull when it comes to the pattern on each feather, is is considered to be European Herring Gulls with reduced or aberrant pigmentation.

It was seen on April 6, 2014.

Herring Gull (Larus argentatus) with reduced pigmentation seen in Grenaa Harbour

Some of these pale type Herring Gulls can recall birds labelled as hybrid hyperboreus x argentatus (Viking Gull), but as this individual lacks a clear influence from Glaucous Gull when it comes to the pattern on each feather, is is considered to be European Herring Gulls with reduced or aberrant pigmentation.

Herring Gull with a grey 'pseudo-mirror' on the underside of P10

In a recent article by Peter Adriaens on Birding Frontiers, a new supporting micro feature was suggested for distinguishing adult American Herring Gulls from European Herring Gulls. It was recently commented upon by Maarten van Kleinwee on his blog Gulls to the horizon based on a selection of great photos.

The supporting character is a grey mirror found on the underside of P9 or P10. It is described as a somewhat isolated grey spot or grey hole inside the black pattern on the underside of P9 or P10. The grey spot is either completely surrounded by black or seen as a grey cut which is open towards the base of the feather. It may be present in both wings at the same time or only in one of the wings.

The feature is apparently rare in European Herring Gull, but has been seen in a few hybrids (or backcrosses) of Glaucous Gull x Herring Gull in Iceland. When looking through my photos of apparent pure European Herring Gulls, I came across this individual which was seen on February 11, 2013 in Vesterø Harbour on the island Læsø in Denmark. It represents the only European Herring Gull that I have ever documented with such a small grey ‘pseudo-mirror’. Note that it is present in P10 on left wing only.

Herring Gulls (Larus argentatus) with reduced pigmentation seen in Hanstholm Harbour

These three Herring Gulls (Larus argentatus) were all photographed on March 31-April 1, 2013 in Hanstholm Harbour.

Some of these pale types can also recall birds labelled as hybrid hyperboreus x argentatus (Viking Gull), but as they lacks a clear influence from Glaucous Gull when it comes to the pattern on each feather, they are all considered to be European Herring Gulls with reduced pigmentation, but it will always be a question whether to name such as aberrant/pale end argentatus or Viking Gull-types.

#1: 31 March 2013, Hanhstholm Harbour, 7 photos below

#2: 1 April 2013, Hanhstholm Harbour, 1 photo below

#3: 1 April 2013, Hanhstholm Harbour, 1 photo below