John Holmes

2009-12-04  NSW
1DMKIIn + 800mm







I could not work out what this was, but Mike Chalmers has kindly commented as follows : -

"Your photo is first winter Yellow-legged Gull race mongolicus = Mongolian Gull. Reasons are :-

1. Relatively narrow well defined black tail band
2. Generally pale upperparts, esp head, rump and upper tail coverts [as well as greater coverts and tertials - see below].
3. Greater coverts have more white than dark in each feather [ dark in form of relatively narrow banding] giving impression of overall paleness contrasting strongly with darker flight feathers
4. Same to tertials which are whitish mostly with relatively narrow dark markings [usually anchor-shaped]
5. Chunky relatively deep bill supports id.

Heuglins would be much darker, as would Slaty-backed. Both would have wider tail bands with almost all of tail black in Slaty-backed.

Seems to have a spot of bother with its left wing with mangled middle primaries.

Have copied this to Geoff (Carey) to see if he wants to add anything.

Suggest you go ahead and post to encourage others. Please keep taking big gull pics. Like I suggested last year, they would be good to illustrate an updated paper on gull id in HK."

[ Last edited by John Holmes at 5/12/2009 07:46 ]

cgeoff

Two things I'd add. Firstly, the narrow second dark band on the tail is something rarely shown so clearly by other taxa. Secondly, note the extensive pale inner primary window. This bird has at least extensively pale inner webs to all but the outer 3 primaries, and even P8 has some pale internally. On vegae, these pale markings do not extend so obviously beyond P5, while on heuglini and Slaty-backed, the wings are more uniform (though the latter, in particular, does often have a paler area on the inner primaries).

Geoff

[ Last edited by cgeoff at 5/12/2009 13:44 ]

mhs

I would like to  ask does it as same as Yellow Legged Gull. Thanks.

17 Nov 2009, NSW

cgeoff

Yes, I would say this is also mongolicus - despite not having a second tail band, nor very extensive pale inner primaries (which highlights how variable gulls can be!).

It does have a relatively narrow tail band and a contrastingly pale head, which in my experience is characteristic of 1y mongolicus at this stage in the first winter; it also has a classic bill shape and size. Further, the upper scapulars of the far wing in the first photo are obviously dark, which is a good feature; these remain visible throughout the first winter.

Very good photos. As said above, Mike and I plan a paper on large gulls in HK, and we encourage people to take as many photos as possible.

Geoff

mhs

Thanks Geoff.