HKBWS BBS 香港觀鳥會新聞組


    
      
        HKBWS BBS 香 港 觀 鳥 會 新 聞 組
        (http://www.hkbws.org.hk/cgi-bin/YaBB.pl)
      

        Discussion Area 討論區 >> Bird Identification 鳥類辨識 >>  Unknown Tern at Tsuen Wan
        
(Message started by: bfspoonbill on Sep 18^th, 2006, 12:23am)

Title: Unknown Tern at Tsuen Wan
Post by bfspoonbill on Sep 18^th, 2006, 12:23am

A group of about 5~6 unknown tern was seen flying along the Rambler Channel at Tsuen Wan, at 8:30am on 16/9 and at 12:30pm on 17/9. Some photos and videos (by poor quality consumer DC) were taken on 17/9 along the foot path from Tsuen Wan Ferry Pier to Tsuen Wan Riveria Park.

Are they Common Tern? We cannot identify. It is surprising  ??? to see tern along this channel of urban area. The flew fast and smooth. They never dived into water for food, just stationary for a little while and touching the surface. Their behaviour was so different from the city birds we'd seen. So, we could not conclude on 16/9, by just naked eyes.

http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170001-a.JPG
http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170003-a1.JPG
http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170004-as.JPG
http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170005-as.JPG
http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170006-a.JPG
http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170007-a.JPG
http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170008-as.JPG
http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170009-as.JPG

A short DC video about their flight can be download here (3.38MB WMV). (http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/Movie.wmv)

Title: Re: Unknwon Tern at Tsuen Wan
Post by Mike Kilburn on Sep 18^th, 2006, 1:22am

I think these are White-winged Terns.

Cheers
Mike K

Title: Re: Unknown Tern at Tsuen Wan
Post by bfspoonbill on Sep 18^th, 2006, 9:39am

Thanks for the comment. Actually, the White-Winged Black Tern and the Common Tern look alike to us. This was the second time we saw real tern. The first time was a Tap Mun visit with HF Cheung. So, we appreciate you expert guys to identify them.

Questions:-

- From HK & S China Bird book, White-winged Black Tern is a visitor in May. It is now mid-September. They should have left HK for homeland area.

- Their non-forked tail and small size rule out many others. But how can remaining tern species be distinguished?

- Is it uncommon to see tern in urban area?

The following photos have large sized image link. You can click the displayed image to view the large one.

http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170003-a1.JPG (http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170003-a.JPG)
The legs are not "black"!? Sorry, the DC quality is this poor. Probably, it matchs the red legs of White-Winged Black Tern.

http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170004-as.JPG (http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170004-a.JPG)
The tail is not forked, actually square look.

http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170005-as.JPG (http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170005-a.JPG)
The head is quite clean white for this one while the back is "dirty".

http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170009-as.JPG (http://everwell.dynu.com:3880/BirdWatching/Unknown-Tern-TW-20060917/P9170009-a.JPG)
The first one (apparently having something in mouth) had clear black tip on underside of wing (in 3.4M-pixel large sized image). But the one above did not have clear black tip. Are they different?

Title: Re: Unknown Tern at Tsuen Wan
Post by gjcarey on Sep 18^th, 2006, 10:12am

The foraging pattern described is typical of a marsh tern, and not a Sterna (Common) Tern.

These terns are, however, Whiskered. The fairly large dagger-like bill, the narrow black line linking eye to nape (different from the usual WWT head markings), the overall pale appearance, the greyish flanks visible on the bird most advanced into winter plumage and the relatively square-cut tail all indicate Whiskered. And wouldn't WWT have a darker carpal area?

Geoff