Odd plumage of a Glaucous-winged Gull

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adriaens
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Odd plumage of a Glaucous-winged Gull

Post by adriaens » Tue Jun 26, 2012 10:00 pm

I am not sure what is going on in this bird. It seems to combine feathers of two different plumage cycles.
My guess would be that it is a first-cycle bird, because most scapulars, lesser and inner median and greater coverts, secondaries and tail feathers all look juvenile to me.
Yet, there appears to be some kind of moult contrast in the primaries, with P9-10 old (juvenile) but P1-8 seemingly of a different, newer generation.
Also, a rather large number of median and - especially - greater coverts appear to be missing (or to have been moulted?).

Anyone who can shed light on this bird's plumage and moult state?

Photos taken at Choshi fishing harbour, Japan, on 10 March 2012.
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GlaucouswingedGull_1c_Choshi_Japan_20120310_014_detail.JPG
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marsmuusse
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Re: Odd plumage of a Glaucous-winged Gull

Post by marsmuusse » Fri Jun 29, 2012 10:08 pm

Hi Peter,
I think you are right. P1-P8 replaced for 2nd gen primaries, P9-P10 still juvenile. Secondaries juvenile, except probably S6, which seems to be 2nd gen.
I don't see missing coverts. GC seem present on image GlaucouswingedGull_1c_Choshi_Japan_20120310_015_detail.JPG (357.97 KiB). Strange moult though, with the inner gc old, and outer gc new (except maybe the outermost feather.). The same seems true for the mc. I think the tertials are still juvenile, leaving this bird in complete converse moult strategy, i.e. If birds show first signs of moult, then normally they start with the feathers which have been unmoulted in this individual. There may be some virus / malnutrition / etc involved; an infection which has stimulated to drop feathers and grow in new feathers. I've seen this phenomenon in a Dutch LBBG colony, where I found juvenile birds (only 2 months old) starting to replace primaries and secondaries, seemingly random. (nest E74, E75 & E76 red ringed: http://www.gull-research.org/lbbg1cy/e74jun.htm ). Two of these birds died pretty soon after leaving the colony. See these birds as well in a 17 minute video about "replacement of coverts in juvenile LBBG still in a colony", video found here:
http://www.gull-research.org/miscellane ... ylbbg.html
on 15:01 minute.

Cheers, Mars

adriaens
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Re: Odd plumage of a Glaucous-winged Gull

Post by adriaens » Sat Jun 30, 2012 5:49 pm

Thanks for the reply, Mars!
Birds like that defy all logic...

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Theo Muusse
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Re: Odd plumage of a Glaucous-winged Gull

Post by Theo Muusse » Tue Sep 25, 2012 9:27 pm

Yes, birds E74 and E76 both were found dead near the end of the autumn, not far from the nest.
Obviously, the moult was a strong reaction to some kind of unhealthy visitor, the birds trying to moult out their problem.
Funny enough, E75, the brother, did not moult a thing and was starting only in August on the expected loci.

Theo

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Theo Muusse
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Re: Odd plumage of a Glaucous-winged Gull

Post by Theo Muusse » Tue Sep 25, 2012 9:32 pm

As said in the movie, LBBG moults more in the colony in comparison with HG.
As we know so far, the behaviour of LBBG chicks appear to be much more adventurous.
Running around and being brave may well have its price.. since HG were observed to be the quiet chicks around, rather hiding than running.
LBBG chicks also tried to beg more from non-parent adults.

Note the shots were the juvenile was molested by a neighboring adult.

Theo

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