Scapular age

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JanJ
Posts: 422
Joined: Mon Oct 12, 2009 10:08 pm

Scapular age

Post by JanJ » Sat May 26, 2018 1:58 pm

Hi!

David Erterius wrote this on FB regarding a 2cy Caspian Gull.

"Just wanna discuss the appearance of many second calendar year Caspian Gulls occuring by mid-late spring here in southern Sweden. To illustrate this, here's an example from Simrishamn, Scania 6 May 2018.

As far as I can judge, this bird exhibits two different types of scapulars, hereafter referred to as "a" and "b".

a) To me, these must be second generation post-juvenile feathers with the typical anchor-pattern on some of the least worn feathers.

b) These feathers are marked differently with prominent shaft streaks and lacking the distinctive "anchors". The lower row of these types consists of less abraded scapulars, as what can be expected due to the more sheltered position. However, the upper group shows a similar wear as the a-group, hence I'm assuming all these b-group feathers were moulted in the same sequence as the a-group or soon after. Alternatively, these are third generation feathers which has been replaced at a later stage.

These are just my thoughts and I might be wrong so please feel free to elaborate on this and share your own thoughts."

I had them as 2gen, but my brain got blury so what´s your opinion?

Jan
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marsmuusse
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Re: Scapular age

Post by marsmuusse » Sun May 27, 2018 7:47 pm

Hi Jan,

Thanks for copying this into the forum discussion. To get a better understanding, it would be ideal to have this very individual photographed several times over the months, to see how the moult progresses and the plumage develops regarding wear and tear. Not this particular cachinnans bird may serve as example, but fortunately I have a very cooperative (ringed) Herring Gull called Y[A||V] at my local beach to come to help. See here:

http://www.gull-research.org/hg/hg1cy/avyellowbars.html

Please scroll down on this page to where 2CY April can be found. The text reads:

below: Herring Gull (argenteus) A||V moult progress in the scapulars.
One of the good things about ringed gulls: throughout the season you're pretty sure the same individual bird is involved all the time.
Therefore you can compare the plumage - like in Herring Gull Y[A||V], between early winter (1CY Oct) and late winter (2CY April), or if you like early and late 1st cycle plumage.
Yellow A||V nicely illustrates three issues:
- By October some 2nd gen scapulars are already slightly bleached to white; these are among the earliest replaced scaps right after the juvenile feathers are dropped.
- By April the feathers at this exact location is obvious greyish, and fresh. This is now 3rd generation.
- By late October the lower scaps are still juvenile, but not anymore in April. Therefore it illustrates that moult in the scaps continues throughout the winter months, albeit at low pace.

It supports also the assumption for 1st cycle Herring Gulls, that "if you find fresh scaps in the upper region or the upper row of the lower region, while the long rear scaps have been replaced, the aforementioned scaps are most probably 3rd gen".

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JanJ
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Re: Scapular age

Post by JanJ » Wed May 30, 2018 5:39 pm

Thanks very much Mars!

Jan :D

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