HKBWS BBS 香港觀鳥會新聞組


    
      
        HKBWS BBS 香 港 觀 鳥 會 新 聞 組
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        Discussion Area 討論區 >> Birding Reports & Tips 觀鳥報告及心得 >>  Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
        
(Message started by: PWMK on Oct 11^th, 2005, 7:59pm)

Title: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by PWMK on Oct 11^th, 2005, 7:59pm

On Po Toi Island & West Lamma Channel
9th Oct 2005

Eurasian Hobby x 1 Juv.
Besra x 1 male
Northern Sparrowhawk x1
Kestrel x 1 female
Crested Goshawk x1 Juv.
Black Kite x 10+
Black-naped Oriole x 1 Juv.
Dark-sided Flycatcher x 1
Grey-streaked Flycatcher x 2
Asian Brown Flycatcher x 1
Yellow-browed Warbler x 1
Eastern-crowned Warbler x 1
Black Drongo x 5
White Wagtail x 3
Reef Egret x 7
Greater Crested Tern x 1
Aleutian Tern x 7
Common Tern x 1
U.I. Tern x 20+
Red-necked Phalarope x 6
Blue Rock Thrush x 1 male

A rather quite day.
PWMK

Title: Re: Po Toi Outing on 9 Oct 05
Post by David_Diskin on Oct 11^th, 2005, 9:10pm

I am interested in the sightings of the two Besras at Po Toi.

I was on the trip and did see two accipiters sp., one much larger than the other.

Could anyone who photographed these birds, please post their photos here (or on the Bird ID site) so that others can comment on their ID.

I am not necessarily disputing the ID, but I must admit to having difficulties with accipiter identification - I find separation of Jap Sparrowhawk & Besra challenging, and I think that separating Crested Goshawk from Besra may also be more of a problem than is currently recognised.

So any photos of the Po Toi birds would, I believe, be very helpful in this regard.

dave diskin

Title: Re: Po Toi Outing on 9 Oct 05
Post by 深藍 Owen on Oct 11^th, 2005, 10:38pm

one of them and i dunno what it is... more quailty even worst that this one coming..

http://www.pbase.com/bluetitan/image/50581845.jpg

Title: Re: Po Toi Outing on 9 Oct 05
Post by 深藍 Owen on Oct 11^th, 2005, 10:44pm

two more..

http://www.hkbws.org.hk/fileServer/PhotoG/owen/owen_150.jpg
http://www.i-owen.com/gallery/albums/misc/IMG_1263.jpg

http://www.hkbws.org.hk/fileServer/PhotoG/owen/owen_151.jpg
http://www.i-owen.com/gallery/albums/misc/IMG_1273.jpg

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by PWMK on Oct 12^th, 2005, 11:51pm

http://www.hkbws.org.hk/fileServer/PhotoG/pwmk/pwmk_042.jpg
http://www.hkbws.org.hk/fileServer/temp/guest/Accipiters.jpg

Hi David,
We also agreed with you that accipiters are very difficult to identify, at least to us.  After checking our photos close up, we can only sure that 'G' is a Common Kestrel and 'H' is an Eurasian Hobby.  

So, the Besra become a questions here ?  Can anyone help, we need some expert's advice, thanks.

PWMK : )

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by David_Diskin on Oct 13^th, 2005, 8:33am

Thanks for the photos - I'm sure they'll prove very useful. One quick question before I chase up the "experts" for their opinions - Were all of these taken at Po Toi on Sunday?

Cheers,

Dave Diskin.

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by PWMK on Oct 13^th, 2005, 8:58am

Yes, they were all taken at Po Toi on last Sunday.

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by HF_Cheung on Oct 13^th, 2005, 2:52pm

I am not claiming that I am an expert. I think the photos are good for two Besras at Po Toi.

First of all, there is little problem identifying them as accipiters. Then, one can see the mesial stripe on the throat, streaks on the breast, bars on the flank, and also dark and light tail bars that are of equal width. I think this is sufficient to identify them as Besras. Since B and D are clearly different, there were at least two birds.

HF Cheung

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by Gary on Oct 13^th, 2005, 5:44pm

A very interesting photo set! Indeed, it's a very good educational material for raptor identification.
I'm not an expert on raptor ID, but I'd like to take this opportunity to learn more about the method for identification of raptor in Hong Kong.
When I watch an accipiter from below, I usually identify it by watching the general shape or wing pattern rather than the underparts pattern. It's useful to separate Crested Goshawk from Japanese sparrowhawk and Besra. The wing pattern of Crested Goshawk is broad and round while Besra and Japanese Sparrowhawk would form a small “notch” at the wing's trailing edge. Photo A,C,D,E and F clearly illustrate this point that you won't think they are Crested Goshawk. However, the rounded wing shape of photo B reminds me of Crested Goshawk. Although the wing shape is not very reliable due to the angle of the photo, I think it's a juvenile Crested Goshawk.
After ruling out the Crested Goshawk, the photo A,D,E and F are either Besra or Japanese Sparrowhawk. A commonly used method to tell the difference is watching the width of the white-and-black band on the tail. The uneven width of the tail band in photo D reveals that it's a Japanese Sparrowhawk. Indeed, I guess it's a juvenile Japanese Sparrowhawk.
Are D,E and F the same bird? They look quite similar to me.
I found photo A is difficult for me as I'm not familiar with the underparts pattern.
After all, the most interesting bird I think is in photo C. A technique that Japanese and Taiwanese people often usually but I seldom heard in HK is counting the fingers (protruded primaries). Besra and Japanese Sparrowhawk both have 5 fingers but Eurasian Sparrowhawk has 6 fingers. If you check the photo C carefully, you can see it has 6 fingers which match Eurasian/Northern Sparrowhawk! Furthermore, the tail of bird C is relatively long and gives a ratio of head & body to tail about 1:1. It looks like a juvenile/female Eurasian Sparrowhawk to me.
In summary, at least 5 birds have been involved in the photo set. Who said it's quiet in Po Toi!
Please advise if you find the analysis flow is wrong.

Gary

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by Paul Leader on Oct 13^th, 2005, 9:08pm

I would say that A, D, E and F are all the same adult male Besra, B is juvenile Crested Goshawk (note the very rounded wing cf the Besra and almost unmarkd underwing coverts) and would agree that C looks very good for Northern. Are better/larger images of this bird, as it looks like it has an unmarked throat, a good super and a dark eyestripe behind the eye, which in terms of plumage would clinch it - although I think structure does already.

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by David_Diskin on Oct 13^th, 2005, 9:36pm

A couple of points. It's possible (at least on my computer!) to save the photo(s) to 'My Documents', open it with 'Windows Picture & Fax Viewer', then use the zoom feature to enlarge the images.

This leads to a loss of definition, but on Picture C the bird does show an unmarked throat and dark eyestripe -confirming that the bird is Eurasian Sparrowhawk as Gary & Paul suggested.

Plumage-wise the other photos, apart from the rather distinctive Crested Goshawk (bulging secondaries, pinched-in towards the body) do appear good for male Besra. However, in photo A the bird seems to have rather pointed, tapering wings - so shape-wise appears closer to Jap Sparrowhawk than Besra. Also in photo D, the paler bars on the spreading undertail seem considerably wider than the darker bars - again a feature (as Gary said) that points towards Jap Sparrowhawk rather than Besra.

Paul obviously has a lot more experience of accipiters in Hk than me, and I'm sure he's right when he says it's a Besra, but perhaps I'm not the only one puzzled by the apparent discrepancies .........

Also, no one has commented on the accipiter with the crow in Owen's photograph. I assume it's the same juv Crested Goshawk as in Photo C. Again, comments would be welcome.

Dave Diskin

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by Webcreeper on Oct 13^th, 2005, 10:23pm

Wow! It's good to see so many enlightening discussions on bird ID.

Thanks and please keep them coming!  :D

嘩！有咁多高手現身說法，實在得益不淺！

多謝指教，並請繼續出招！ :D

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by HF_Cheung on Oct 13^th, 2005, 10:41pm

Thank you, Pual, Gary and David. I also like to say that bringing a good camera is very important these days, without which we would not have learned so much.

HF Cheung

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by PWMK on Oct 13^th, 2005, 10:49pm

Thank you all for the identification, we have learnt alot.

cheers

PWMK
;D

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by Paul Leader on Oct 14^th, 2005, 11:37am

I still think A is a male Besra as the plumage features that are visible are never shown by Japanese Sparrowhawk. I you look at the head pattern, underparts patterning and the underwing patterning they are the same as the bird in D, E and F. Also the wing formula is the same as D, E and F(primaries 3 and 4 being joint longest follwed in order by primaries 5, 2 and 1 - and note also their relative lengths).

I think the differences in structure are due to the difference in the mode of flight in the various photographs. Most birds of prey will appear rounder and broader winged (and thus also slightly shorter tailed) in soaring flight, and show narrower, more pointed wings (and thus also a slightly longer tail). I find this especially the case in smaller birds of prey.

It is important to remember that the tail pattern differences for separating Besra and Japanese Sparrowhawk applies to the upperside of the tail only, I have also trapped on or two birds in the past couple of years which show that sadly, this feature is not diagnostic.

Title: Re: Po Toi Outing on 9/10/05 蒲台島觀鳥活動報告
Post by David_Diskin on Oct 14^th, 2005, 1:15pm

Many thanks to Owen, and Peter and Michelle for sending in the photographs in response to my initial request.

Also many thanks to HF Cheung, Gary and Paul (and also to Mike Leven who emailed me) for commenting on the photos.

Interestingly, although there are several photos elsewhere on BBS of Crested Goshawk in flight, and a couple of Japanese Sparrowhawk in flight, I couldn't find any of Besra in flight.

Personally, I found the photos (and ensuing comments) very instructive indeed.

Again - thanks!

Dave Diskin