August 29, 2011
Ageing of the Technopole Franklin’s gulls – expert view
Thanks to Klaus Malling Olsen, author of “Gulls of Europe, Asia and North America” for these comments on the photos of the three Franklin’s gulls in the previous post. What Klaus calls “second calendar year” is my “first summer”; i.e. a bird hatched in 2010. The two terms are confusingly used interchangeably, though Klaus’ term is more logical and less open to ambiguity, as birds could be hatched in various seasons.
Ageing Franklin´s Gull more than one years old is often difficult; they have a dissimilar moult than other gulls, and considering the large individual variation in primary pattern in – apparently – adult birds, it will be safer to label these birds as 2nd cal. year “type”.
Franklin´s Gull 1-year birds moult head and body as well as flight feathers and tail (although a few – sometimes 50%+ – of primaries bat be left unmoulted, resulting in uniform brown and faced wing-tip). Birds which has renewed the entire plumage basically are as adult, apart from minor differences in wing-pattern (dark pattern in primary coverts, more extensive and diffusely offset dark wing-tip, narrower white tips to primaries), all of which are hard to see here. However, the primariries in all three birds seem to lack the broad white tips of even worn adults, making 2nd. cal. year the absoloute most posssible.
A head-pattern as seen here (“winter-head”) is to be expected in 2nd cal. year. Most adults moult head into winter plumage a little later, but early moulters will show a similar head.
I think all three birds (an amazing find!) are 2nd. cal. year birds. But again, a 100% ageing is not fully possible without seing the spread wing – also, it is common in vagrant Franklin´s to show an atypical moult, adapted to their “new surroundings”.
Anyway, finding three birds within a week is amazing, congratulations from here and
all the best
PS! You are most welcome to add my comments on the web
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Header photo: Cap Vert IBA, Dakar
The defunct, twin volcanoes of Mamelles, in Dakar's Ouakam arrondissement, with Cape Verde Shearwaters and Bottle-nosed Dolphins. The rocky coast of Dakar, forming the Cap Vert Important Bird Area, is an outstanding site for seabirds (photo: P. Robinson)
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