查看完整版本: Tern's ID please

fatchun 18/08/2010 20:12

Tern's ID please

[img]http://lh3.ggpht.com/_gKlwPk4F2go/TGvNmj69clI/AAAAAAAAAoQ/HktCt4JEbJI/DSC_0902.JPG[/img]

Is it juv. Roseate Tern? or Common Tern? Thank you

4 more photos, Thank you

[img]http://lh5.ggpht.com/_gKlwPk4F2go/TG6zt1i3coI/AAAAAAAAAok/hep4O2ddIjM/DSC_09042.jpg[/img]

[img]http://lh3.ggpht.com/_gKlwPk4F2go/TG6z4bf7RSI/AAAAAAAAAoo/Wc1i4Mu4SE8/DSC_09002.jpg[/img]

[img]http://lh4.ggpht.com/_gKlwPk4F2go/TG6z4zB255I/AAAAAAAAAos/WmCVxr0reuI/DSC_09012.jpg[/img]

[img]http://lh5.ggpht.com/_gKlwPk4F2go/TG6z5YWRWdI/AAAAAAAAAow/7qgik7BjQKg/DSC_09052.jpg[/img]

[[i] Last edited by fatchun at 21/08/2010 00:59 [/i]]

HFCheung 20/08/2010 11:59

ID on a photo is not always easy, since the size is often difficult to get, and one get only a limit number of view.  Like this one, I am not quite sure of the size, which would help to eliminate some possibility.  If the choice is among Roseate and Common, the photo certain favour Roseate in non-breeding plumage.  However, I am not sure others are totally eliminated, like Arctic Tern.  The bill looks short to me for Roseate.  May be that is an effect of the angle of view.

HF Cheung

fatchun 20/08/2010 15:31

Thank you very much!!
Attached is 1 more photo and the tern behind is black-naped tern. I hope this can help to id this tern.

[attach]6943[/attach]

lrichard 20/08/2010 17:35

Could this be a Sandwich Tern?

ddavid 20/08/2010 21:13

When and where was the photo taken?

david

fatchun 20/08/2010 22:35

[quote]Original posted by [i]ddavid[/i] at 20/08/2010 21:13 [url=http://www.hkbws.org.hk/BBS/redirect.php?goto=findpost&pid=32408&ptid=11983][img]http://www.hkbws.org.hk/BBS/images/common/back.gif[/img][/url]
When and where was the photo taken?

david [/quote]

On 17th this month, just near Tapmun, Thanks

fatchun 21/08/2010 01:00

4 more photos have been uploaded and I hope that can help us to ID it, thank you very much!

lrichard 21/08/2010 20:48

Thanks for posting the extra photos, Fatchun.

The 4th one shows a bird whose legs are obviously orange or red, totally the wrong colour for Sandwich Tern (should be black). However, I'm still not sure of the ID of the bird.

ddavid 21/08/2010 23:12

I'm no expert but I think this a very difficult bird to ID. I can see why Richard suggested Sandwich Tern - the wing pattern fits 1st-summer Sandwich and there does seem to be pale tip to the bill in the photos. However, the "jizz" doesn't seem quite right to me (very subjective) and, as Richard points out, the leg colour in one of the photos is wrong for Sandwich.

Also, of course, HK is way out of range for Sandwich, which doesn't usually occur east of Sri Lanka - although Mark Brazil includes the species in [i]Birds of East Asia[/i] on the basis of  a record from Taiwan.

My own personal feeling is that this is an odd Roseate Tern in non-adult plumage (1st-summer? 2nd-summer?) -  but I wouldn't bet my life, for what it's worth, on that assessment.

david

[[i] Last edited by ddavid at 21/08/2010 23:16 [/i]]

fatchun 21/08/2010 23:56

Thank you very much! Thank you for all comments!
I agree with David that it is too far for Sandwich tern to come to HK. This tern is so strange to me that the combination of all evidence cannot suggest any tern to me at the first glance. I know this is difficult to ID a tern especially the 1st winter/ 2nd winter/non-breeding with only some angles of photos. By the way, thank you again3551smile445

ddavid 22/08/2010 00:17

I'm not sure. If Sandwich Tern can turn up in Taiwan, then it could turn up in HK. Also, if say your 4th photo was the only photo you had, then I would probably say it was definitely a Sandwich Tern!!

It is a very difficult bird to ID - but I'm sure, given your photos, it will be pinned down in the end.

All the best

david

tmichael 22/08/2010 05:39

Been thinking about this one for a couple of days, and I've come back to my original view on this one - surely it's the species it is most likely to be anyway, ie Roseate Tern, presumably a bird born this year, but which has already assumed full winter plumage (?? as I've not checked moult timing details).

Although there's a hint of Sandwich Tern jizz in the fourth picture - really just that the crest appears a little 'floppy'? - that's the picture showing pale (washed out, dirty orangish?) legs and feet, which seems wrong for Sandwich, but in any case in none of the others does it do it for me jizz-wise as Sandwich Tern, and I saw a few in UK as recently as the first week of this month (+ I've seen thousands and thousands over the years).

I think also,without going into massive detail, the wing pattern - narrow dark leading edge above all - is classic Roseate and never shown by Sandwich (or Arctic, for which a few things look wrong) as far as I can see.

Wasn't it great to get those extra images! Thanks Fatchun

My main reference btw has been Collins Bird Guide (Britain and Europe) currently on sale from the Society I believe, and at a favourable price to members - highly recommended. and in the future all field guides will be that good or even better!

Finally it's NEVER 'too far' for things like terns, or any highly migratory bird to go anywhere - 31 years ago an Aleutian Tern came to my native North-east England, probably even more amazing than Sandwich Tern would be in HK (+Ancient Murrelet, Long-billed Murrelet, Tufted Puffin, Yellow-nosed Albatross, Sooty Tern and Bridled Tern - several -  have all occurred thousands of miles out of range in UK in my birding lifetime).

Mike Turnbull

[[i] Last edited by tmichael at 22/08/2010 05:40 [/i]]

lrichard 22/08/2010 06:09

Interesting bird.

The date of the one Taiwan record of Sandwich Tern - 29 August 2005.

ajohn 22/08/2010 12:04

Like others, I've been puzzling a bit over this bird. I can see why Sandwich was suggested, but I don't think the structure is right and I don't think the pale tip to the bill is well defined. Plus, as richard pointed out, the red legs rule out sandwich.

The problem comes from the fact that this is a bird in winter plumage, which we are not familiar with in this part of the world. I don't think it's a bird from this year, which should show at least some juvenile plumage - I think it's actually a full adult. My initial feeling was that this would turn out to be a Common Tern in winter plumage. Now I don't think that's right though - I don't think the underwing pattern is right for Common. Like others, I suspect this is actually a Roseate Tern, which has already moulted out of breeding plumage.

ddavid 22/08/2010 12:38

Olsen & Larsson in [i]Terns of Europe and North America[/i] (1995) write that Roseate Tern adults have a complete moult to winter plumage from June-July. Therefore any adults seen in August should (theoretically) already be in full winter plumage. Hence this bird may well be, as John suggests, a winter plumage adult Roseate Tern. I also agree that the wing pattern does not fit Common Tern.

david

fatchun 22/08/2010 16:09

Thank you Richard, John and David for your detail information and discussion.

After thinking of the structure, plumage and body coloration, a question was raised in my mind.
Would it be a hybrid of any terns?(e.g. Common tern and Roseate tern)

Thank you very much

ddavid 22/08/2010 17:56

Apparently there are records of hybridisation between Common and Roseate terns in the USA and Europe. However, in this part of the world, I think there is little overlap (if any) in their breeding ranges.

I think the difficulty with this bird is, as John points out, simply because we aren't very familiar with the winter plumage of Roseate Terns. Most birders/photographers in HK see them in summer plumage on their breeding islands. The terns seem to leave the territory fairly early - I don't recall seeing any on the boat trips organised by the HKBWS in September - Common Terns & Aleutian Terns yes, but not Roseate.

So, all in all, an instructive set of photographs and an interesting discussion.

david

[[i] Last edited by ddavid at 22/08/2010 17:58 [/i]]

lpaul 23/08/2010 09:22

I think this is certainly a Roseate Tern.  In addition to the features discussed by others, I think there is single diagnostic feature which has not been pointed out by others and that is the pattern of the outer tail feather.  In Common and Arctic terns the outer web is black and forms a very narrow but obvious black line along the outer edge of the tail.  In Roseate Term This is white and contrasts with the rest of the tail which is slightly greyer.  This is well shown in the photos.

Regarding age, I think this is probably a first summer rather than an adult.  I think that given that wing moult has only just started (inner only primaries being replaced) it seems unlikely that body moult would be as advanced as this (i.e completed) if this was an adult.  The bill colour and leg would also be very advanced into winter 'plumage' for an adult.

A very interesting bird.  Thank you for posting the photos.

fatchun 23/08/2010 18:43

I am so happy that this tern can arouse a interesting discussion! I think the interest of birding is like that, discussing, thinking and observing. I can say I am just a junior bird watcher, and some points that some of you have mentioned are not being considered before by myself. Thank you very much, I have leart many from this discussion!=]

Chun

thinfor 26/08/2010 13:18

I also learnt a lot from you all.  Thanks very much. :)
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