new caspian gull in denmark (1 Viewer)

[Kent Olsen]

Today we found a new Caspian Gull in Aarhus and while shooting documentation the Glaucous-winged Gull was relocated just further behind (been away for 24 days), crazy

Everybody agree with the cachinnans ID?

http://gulldk.blogspot.com/2009/12/caspian-gull-larus-cachinnans-4k.html

Kent

 

[Cristian Mihai]

Seeing the bird on water I would say it's definitely a Caspian Gull, but seeing the wing tip I wouldn't...

 

[lou salomon]

hi kent,

it has a short p10 tongue on underside and a solid subterminal band to the p10 mirror but that's because it is a you g adult: 4-5cy another sign of immaturity is the dark streak on a primary covert. i'd call it a caspian.

cheers,

 

[Cristian Mihai]

Yeah, a 4cy-5cy bird it's a good solution for you problem, Kent. As usual, Lou has the key.

 

[JANJ]

As Lou mentioned, the mirror on p10 is usually evident in younger subadults
However, some adult (looking) birds have a mirror on p10, which is usually explained as being eastern Caspian's. The 'trademark' - all white tip on p10 in Caspian is a good feature in most seen in WE, given the ones with a mirror. Sometimes the dark subterminal mark on p10 is very thin or just seen on the outer or inner web.

http://waarneming.nl/foto/view/966166

Check the last bird here:

http://www.talk.gull-research.org/viewtopic.php?f=14&t=49&start=10

JanJ

 

[lou salomon]

kent, jan,

even in 'ponticus' (black-sea population) there is a certain percentage of adult looking breeding birds with a solid subterminal mark to p10 (i don't want to give percentages because my sample of pics maybe is not large enough, but i'd say approximately 5-10 %). we don't know how much exchange there is between western and eastern cachinnans though. it's merely a speculation that birds with extended black are from a more easterly origin.

upperside black in wingtip is much more extended in caspian than on the underside and i have many pics where you can't say if it's a michahellis or a cachinnans from above - you need a look on the underside. this is such an example (but the rest of the bird is perfect for cachi) - it could be an eastern bird, pic taken in february:
http://lou.bertalan.de/birds/pic/hi/up_0174.jpg
http://lou.bertalan.de/birds/pic/hi/up_0173.jpg
http://lou.bertalan.de/birds/pic/hi/up_0175.jpg

see the attached bird photographed in a breeding colony in romania in spring - the amount of ventral black in wingtip is frightening.

all the best,