Plumage differences in Dutch 4cy Lesser Black-backed Gulls – May/June 2014

The images below are of 4 Lesser Black-backed Gulls Larus fuscus graellsii (Dutch intergrade), all ringed in July 2011 as pullus in the colony of IJmuiden (Forteiland), the Netherlands.

4th-calendar year Lesser Black-backed Gulls can be notoriously difficult to age because they can look very adult like, especially when seen in rest.

This is proven by Green Y.AWL which looks very much like an adult: hardly to no brown in the coverts, large white tips to the primaries, a large mirror on P10, a fully white tail and no primary moult yet (in line with most adults at this time of year).

The others show much more sub-adult features: much brown in the coverts, small to none white primary tips,  a small mirror on P10, dark markings in the tail and inner primary P1 dropped.

Here a comparison of the main features per ringed individual:

Code Tertials Coverts Primary tips P10 mirror Bill markings Tail Primary moult
Y.AWH Brown Mix of brown and adult, much black on the primary coverts. Small white spots. Small Black on upper mandible only. Small black spots. P1 dropped.
Y.AWL Adult Adult looking, black on primary coverts. Large white spots. Large Black on both mandibles. Fully white. None.
Y.AWN Adult Predominantly brown. No white spots. Very small Faint black markings on both mandibles. Small black spots. P1 dropped.
Y.AZA Adult Adult looking. No white spots (or very worn). Large Faint black markings on both mandibles. Much black. None.

All photos were taken at the end of May/beginning of June 2014 in the gull colony of IJmuiden where they were ringed.

G[Y.AWH]-20140526-2

Green Y.AWH

G[Y.AWL]-20140519

Green Y.AWL (with dirt on bill)

G[Y.AWL]-20140519-2

Green Y.AWL

Green Y.AWN

Green Y.AWN

Green Y.AZA.

Green Y.AZA.

Green Y.AZA.

Green Y.AZA.

Green Y.AWH

Green Y.AWH

Green Y.AWL

Green Y.AWL

Green Y.AWN

Green Y.AWN

Green Y.AWN

Green Y.AWN

Green Y.AZA

Green Y.AZA

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One thought on “Plumage differences in Dutch 4cy Lesser Black-backed Gulls – May/June 2014

  1. To be honest, the majority of those – aside from the last photo, I would probably have just have assumed were adults without a second thought…

    Also, Green Y.AWN – those spikes!

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