Larus cachinnans

(last update: February 16, 2013)

Coordinator:
Peter Adriaens (Belgium)
Ies Meulmeester (Netherlands)

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cachinnans plumages

Larus cachinnans (hybrid?) 4P41 sub-adult, May 07 2014, Zastów Karczmiski, Poland. Picture: Łukasz Bednarz ringing team.

Location: Zastów Karczmiski, Poland - colony at the banks of the Middle Vistula river.
In 2004 240 breeding pairs (95% cachinnans, <5% argentatus). (Ornis Fennica 2011 88, 80-89) and in 2012 592 pairs (90% cachinnans, <10% hybrid / argentatus) and possibly Larus michahellis (pers comm. Łukasz Bednarz).

Middle Vistule river is a location where several taxa breed: see composition. Since this is a mixed breeding population where hybridisation is not uncommon, the ringing centre in Poland decided to label birds "Larus argentatus sensu lato". Still bulk of the breeding birds in Middle Vistula region show features of cachinnans.

Breeding bird trapped at the nest. Sub-adult, with obvious immature markings on primary coverts, probably 4CY. Putative cachinnans, which may have some hybrid aspects.
Bird with dense speckling in iris. Red orbital ring and gape. No red on upper mandible; black on the upper and black on the lower mandible. Pink legs with yellow hue. Hing bill, with obvious gonys angle (not classic for cachinnans).
Moderate greyish tongue on P10 (medial band is obviously broader than white tip, but pattern still may change with age; full subterminal band and black on innerweb reaching to primary coverts), and black band on P5 broken by shaft; no black spot on P4. P1 dropped; PMS=1.