Scoring primary feathers of European Herring Gulls

Last Sunday (May 6, 2012) I helped out with ringing European Herring Gulls (Larus argentatus) and Lesser Black-backed Gulls (Larus fuscus) in one of the colonies in the Rotterdam Europoort area (Dintelhaven).

During this session, 50 individuals were caught (15 Herring Gulls and 35 Lesser Black-backed Gulls) by trapping them on their nest using walk-in cages.

A walk-in cage, placed over a Herring Gull nest built in a man-made hole; an unusual location for a gull to build its nest. One of the parents was later caught and ringed as Orange WG.

After being caught, the gulls were ringed, their wing length was measured, their sex determined and photographs were taken.

Primary patterns as an identification feature

Herring Gulls breeding in The Netherlands are of the European Herring Gull variety Larus argentatus argenteus, with features that overlap with the northern subspecies Scandinavian Herring Gull Larus argentatus argentatus.

Dutch Lesser Black-backed Gulls are considered to be of subspecies Larus fuscus graellsii, often referred to as the ‘Dutch intergrade’ version because their upperpart grey tone color is intermediate between the British Lesser Black-backed Gull Larus fuscus graellssii and the Baltic Lesser Black-backed Gull Larus fuscus fuscus.

An interesting study was held in 2005 and 2006 investigating how the characteristics found in Dutch Herring Gulls and Lesser Black-backed Gulls can be used as an aid to positively identify the different subspecies. (Phenotypic characteristics and moult commencement in Dutch Herring & Lesser Black-Backed Gulls, Muusse, M., Muusse, T., Buijs, R.-J., Altenburg, R., Gibbins, C. and Luijendijk, B.-J., SEABIRD 24 (2011): 42–59.)

I will apply some of their scoring methods on the individuals that I have photographed (note that the scores are based on the photos taken, not on observations with the bird in hand).

The following characteristics are scored:

1. Black on greater primary coverts
2. Number of primaries with black pigmentation
3. P10 and P9 primary pattern:
I: No mirror
II: Mirror on one web
III: Full subterminal black band, mirror on both webs
IV: Subterminal black present, but band broken
V: No subterminal black, mirror completely merged with tip.
VI: ‘Thayeri’ pattern, medial band not reaching the feather-edge of the inner web (long grey tongue, joining the white mirror)
4. P5 primary pattern
I: No black
II: Diffuse black on outer-web
III: Sharp triangle on outer-web
IV: Sharp triangle on outer-web, diffuse line on inner-web
V: Complete band
5. Primary moult score. See explanation.

#1 can serve as an indication of age (large amounts of black are usually only present in sub-adults), whereas #2-5 are thought to be possible characteristics for separating different subspecies.

Unfortunately, no exact age information is known about these individuals, other than the fact that they have all been identified as adults (older than 4th calendar year).

In this post: Herring Gulls (the Lesser Black-backed Gulls are discussed here.)

Herring Gulls (Larus argentatus argenteus)

Characteristics of interest are marked in blue.

Individual ringed as Orange 1R

Left and right wing pattern of European Herring Gull ringed as Orange 1R. The Netherlands, 6 May 2012.

Black on greater primary coverts: none.
Number of primaries with black pigmentation: 5 (P6-P10).
P10 and P9 primary pattern:
P10: V – No subterminal black, mirror completely merged with tip.
P9: VI – ‘thayeri’ pattern, medial band not reaching the feather-edge of the inner web.
P5 primary pattern: I – No black.
Primary moult score: 0 (all primaries present).

An interesting individual because of the Thayeri pattern on P9: notice how the light grey runs almost along the full length of the outer web. Only a small minority of European Herring Gulls show this pattern, which is more a characteristic of a Scandinavian Herring Gull (Larus argentatus argentatus) and even more of an American Herring Gull (Larus smithsonianus).

Compare this pattern to those in the images below showing a more characteristic pattern for a European Herring Gull, where the black runs to the outside of the feather about half-way down.

I’ve only once before observed a Thayeri pattern: on Scandinavian Herring Gull ringed as White KH89.

Individual ringed as Orange 2R

Wing pattern of European Herring Gull ringed as Orange 2R. The Netherlands, 6 May 2012.

Black on greater primary coverts: none.
Number of primaries with black pigmentation: 6 (P5-P10).
P10 and P9 primary pattern:
P10: IV – Subterminal black present, but band broken.
P9: III: Full subterminal black band, mirror on both webs.
P5 primary pattern: II – Diffuse black on outer-web.
Primary moult score: 0 (all primaries present).

Individual ringed as Orange 3R

Wing pattern of European Herring Gull ringed as Orange 3R. The Netherlands, 6 May 2012.

Black on greater primary coverts: none.
Number of primaries with black pigmentation: 6 (P5-P10)
P10 and P9 primary pattern:
P10: IV – Subterminal black present, but band broken.
P9: II – Mirror on one web.
P5 primary pattern: V – complete band.
Primary moult score: 0 (all primaries present)

The W-pattern on P5 is interesting for a European Herring Gull: although not uncommon, European Herring Gulls usually have a single black mark on the outer web of P5.

Individual ringed as Orange MG

Wing pattern of European Herring Gull ringed as Orange MG. The Netherlands, 6 May 2012.

Black on greater primary coverts: none.
Number of primaries with black pigmentation: 6 (P5-P10).
P10 and P9 primary pattern:
P10: III – Full subterminal black band, mirror on both webs.
P9: III – Full subterminal black band, mirror on both webs.
P5 primary pattern: II – Diffuse black on outer-web.
Primary moult score: 0 (all primaries present).

Individual ringed as Orange OG

Wing pattern of European Herring Gull ringed as Orange OG. The Netherlands, 6 May 2012.

Black on greater primary coverts: none.
Number of primaries with black pigmentation: 6 (P5-P10).
P10 and P9 primary pattern:
P10: V: No subterminal black, mirror completely merged with tip.
P9: II: Mirror on one web.
P5 primary pattern: IV – Sharp triangle on outer-web, diffuse line on inner-web.
Primary moult score: 1 (P1 possibly missing).

Individual ringed as Orange PG

Wing pattern of European Herring Gull ringed as Orange PG. The Netherlands, 6 May 2012.

Black on greater primary coverts: none.
Number of primaries with black pigmentation: 6 (P5-P10).
P10 and P9 primary pattern:
P10: V: No subterminal black, mirror completely merged with tip.
P9: IV: Subterminal black present, but band broken.
P5 primary pattern: II – Diffuse black on outer-web.
Primary moult score: 0 (all primaries present).

Individual ringed as Orange UG

Wing pattern of European Herring Gull ringed as Orange UG. The Netherlands, 6 May 2012.

Black on greater primary coverts: none.
Number of primaries with black pigmentation: 6 (P5-P10).
P10 and P9 primary pattern:
P10: III: Full subterminal black band, mirror on both webs.
P9: II: Mirror on one web.
P5 primary pattern: III – Sharp triangle on outer-web.
Primary moult score: 0 (all primaries present).

Individual ringed as Orange XG

Wing pattern of European Herring Gull ringed as Orange XG. The Netherlands, 6 May 2012.

Black on greater primary coverts: none.
Number of primaries with black pigmentation: 6 (P5-P10).
P10 and P9 primary pattern:
P10: III: Full subterminal black band, mirror on both webs.
P9: II: Mirror on one web.
P5 primary pattern: II – Diffuse black on outer-web.
Primary moult score: 1 (P1 missing).

Discussion
Even with such a low number of individuals, it is interesting to see the huge amount of variation in pattern and moult strategy (as proven in more scientific form in the referred report). It is good to be aware of such small differences and it will be interesting to compare these with individuals in other colonies and/or subspecies.

References

Phenotypic characteristics and moult commencement in Dutch Herring & Lesser Black-Backed Gulls, Muusse, M., Muusse, T., Buijs, R.-J., Altenburg, R., Gibbins, C. and Luijendijk, B.-J., SEABIRD 24 (2011): 42–59.

Identification of adult American Herring Gull, Peter Adriaens & Bruce Mactavish, Dutch Birding 26: 151-179, 2004.

Wing-tip patterns, Gull-Research.org