Moult in graellsii & intermedius

(last update: 08 december 2003)

Herring Gull argentatus
Herring Gull argenteus
Herring Gull smithsonianus
Great Black-backed Gull marinus
Lesser B-b Gull graellsii / intermedius
Lesser B-b Gull fuscus
Yellow-legged Gull michahellis
Yellow-legged Gull atlantis
Caspian Gull cachinnans
Armenian Gull armenicus
Baraba Gull barabensis
Heuglini's Gull heuglini
Vega Gull vegae
Mongolian Gull mongolicus
Slaty-backed Gull schistisagus
.
Black-headed Gull ridibundus 
Grey-headed Gull cirrocephalus 
Brown-headed Gull brunnicephalus 
Bonaparte's Gull philadelphia 
Little Gull minutus
Mediterranean Gull melanocephalus
Relict Gull relictus
Audouin's Gull audouinii
Slender-billed Gull genei
Common / Mew Gull canus
Ring-billed Gull delawarensis
Franklin's Gull pipixcan
Laughing Gull atricilla
Kittiwake Rissa tridactyla
Ivory Gull Pagophila eburnea
Ross's Gull Rodosthetia rosea
Sabine's Gull sabini
Great Black-headed Gull ichtyaetus
Sooty Gull hemprichii
White-eyed Gull leucophthalmus
Glaucous Gull hyperboreus
Iceland Gull glaucoides
Thayer's Gull thayeri
Kumlien's Gull kumlieni
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Skua's Catharacta / Stercorarius
Terns Sterna
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Undoubtedly, some overlap exists between the primary moult in fuscus and intermedius. Peter catches many LBBG in Britain and comments on his picture: "This photograph is of a very dark individual we trapped on the 17 August 2000. The bird has just dropped P1-P3, thus if seen in the field would undoubtedly been claimed as nominate fuscus. To me this bird had recently arrived on passage and commenced its primary moult. We have only one record of a adult graellsii exhibiting this same score and pattern in August. Usually it is only immature birds which exhibit this pattern and only during late May - June.
I have also made the following comment in my paper "According to Baker (1993) "Some (Fenno-Scandia) birds are known to arrest wing moult so that pre-breeding moult includes completion of primary moult, the inner ones being replaced twice during the one moulting cycle." However, there is no evidence, as yet, to suggest that this behaviour applies to British graellsii."

It would be nice to hear from Scandinavian birders the evidence for the above phenomenon. It would also be nice to know whether the evidence for this statement was based on trapped and ringed individuals.

Peter continues: "Suspended moult mainly involves adult birds and during the breeding season. It is not common in immature birds. We have found resumption of moult after suspension in only three second summer birds, and both suspended and resumption of primary moult in seven third summer birds. No first summer birds have been found in suspended moult. Suspended moult therefore appears to be mainly associated with breeding birds. Though having said that, I have found captive non-breeding adult birds in suspended moult. About 10% of adults caught during the breeding season were found to be moulting normally, thought whether they were breeding or not was not established."

Back to arrested / suspended moult in graellsii & intermedius.