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        Discussion Area 討論區 >> Bird Identification 鳥類辨識 >>  Short-tailed Shearwater
        
(Message started by: Yat-tung YU on Apr 25^th, 2006, 1:01am)

Title: Short-tailed Shearwater
Post by Yat-tung YU on Apr 25^th, 2006, 1:01am

Three dark shearwaters were seen during the seabird survey on 23 April 2006. The last one was seen and photographed in close range and below are the photos of this bird.

http://www.hkbws.org.hk/fileServer/PhotoG/Tung/tung024.jpg

http://www.hkbws.org.hk/fileServer/PhotoG/Tung/tung025.jpg

http://www.hkbws.org.hk/fileServer/PhotoG/Tung/tung026.jpg

Southwest of Lamma Island, 23 April 2006

We concluded it as a Short-tailed Shearwater, based on:

1) Dark underparts and small size rule out Streaked Shearwater.
2) Fine bill with steep forehead is favour to Short-tailed, but not Sooty and Wedge-tailed Shearwaters.
3) First picture shows the protruded feet - the best feature for Short-tailed Shearwater.
4) No pale area on both upper and under wings (Sooty Shearwater could show silvery grey coverts on underwings).
5) Tail is not long, nor taped, that is not favour to Wedge-tailed Shearwater.

Any comment is welcome.

Yat-tung Yu

Title: Re: Short-tailed Shearwater
Post by geoff_welch on Apr 25^th, 2006, 5:09pm

This is obviously the same species, and may even be the same bird, that I saw later off Po Toi and mistakenly thought was an all black large petrel (sorry to cause any heart attacks). This is what I saw

http://www.geocities.com/geoffwelch46/s1.jpghttp://www.geocities.com/geoffwelch46/s2.jpghttp://www.geocities.com/geoffwelch46/s3.jpg

But what about this one?

http://www.geocities.com/geoffwelch46/ss1.jpghttp://www.geocities.com/geoffwelch46/ss2.jpghttp://www.geocities.com/geoffwelch46/ss3.jpg

I saw 3 early this morning from Po Toi and another later from the Aberdeen ferry. To me. it seems a lighter brown than the one on Sunday - maybe a trick of light. Anyway, there is clearly a shearwater migration now on in SE Hong Kong waters.

Title: Re: Short-tailed Shearwater
Post by Yat-tung YU on Apr 25^th, 2006, 7:29pm

Hi Geoff,

The birds from this morning are interesting. Wing length, body thickness and their proportion seem not same as my bird. Silvery grey on underwing coverts is very clear in the picture, regardless the darkness of the picture.

These seem fit to Sooty Shearwater.....

Anyway, very good observation!

Thanks for posting these interesting pictures.
Tung

Title: Re: Short-tailed Shearwater
Post by geoff_welch on Apr 25^th, 2006, 7:51pm

Thanks. I also believe they may be Sooty. Not just the pale underwing, but also the paler colour.
According to Harrison's book on 'Seabirds', 'In winter quarters (which both Sooty and Short-tailed are here in Hong Kong), Short-tailed appear darker, more evenly coloured than Sooty, more velvety brown on the upperparts'. That would certainly apply to these birds.

Title: Re: Short-tailed Shearwater
Post by HK_Twitcher on Apr 25^th, 2006, 8:39pm

Geoff/Tung

I believe that both the birds are Short tailed Shearwaters. If you look at the paper on the webb which has some really good pictures and photos it discusses the amount of white on the underwing

http://thebirdguide.com/pelagics/book/id_sosh_stsh.htm

My basis for believing this is that the white in the under wing is two extensive.

In Sooty it is a white flash restricted to the interior wing whereas in Short tailed Shearwater it covers the whole under wing including.

Also I think that the bill would apear heavier and longer.

Of course I may be wrong

Graham

Title: Re: Short-tailed Shearwater
Post by miket on Apr 25^th, 2006, 8:39pm

Tung and Geoff,

Confident separation of Sooty and Short-tailed is acknowledged to be difficult, but I have to disagree with both of you concerning the likely identity of Geoff's birds, which I believe are the same species as the three we saw. I believe all are Short-tailed.

Internet and other researches (for example at http://listserv.arizona.edu/cgi-bin/wa?A2=ind9712a&L=birdwg01&T=0&P=1906)
suggest that while Sooty usually shows silvery-white underwing areas, Short-tailed is much more variable in this respect - there are after all 23 million or so of the things still kicking around. In any case though, they always seem to show a pale underwing - any of the Aussie books and seabird guides show that - and this is all that Geoff's second bird shows.

There are many images available on the Net. Here are some showing the underwings of Short-tailed:
http://www.odolep.com/Australia/Australian%20Seabirds/short-tailed%20shearwater%202844.jpg

http://meyersm.home.mindspring.com/Northern_California/Short-tailed_Shearwater.jpg

http://www.ericwpreston.com/ShortTailedShearwater_1.html

http://www.montereybay.com/creagrus/MtyBaybirds.html

I think the best thing I've come across is at:

http://www.virtualbirder.com/ncal/shearwaterid.html

Although there is apparent uncertainty even from such a widely travelled seabirder as Angus Wilson here, to me, as to others we appear to have a picture of both species side by side here - to cut an increasingly long post short, take a look at the bill and head/neck shape. I know which one I think our well-photographed bird looked like!

I'm really confident of the response you'll get from Oz, Tung, but we'll have to wait and see.

Mike Turnbull.

Title: Re: Short-tailed Shearwater
Post by miket on Apr 25^th, 2006, 8:51pm

Just by way of a footnote the last bird (photographed this morning?) is clearly operating in much stronger winds than we were in on Sunday, when they were very light indeed for shearwaters to be moving in. I believe a Sooty (of which I've seen several hundred at least in UK) would look less bull-necked and longer and straighter winged in this mode of flight.

Mike Turnbull

Title: Re: Short-tailed Shearwater
Post by geoff_welch on Apr 25^th, 2006, 9:41pm

OK, I accept your comments.
The plumage on Short-tailed is very variable and can go from the very dark (like the first bird) to quite light (like the birds I photographed). So, as the first is Short-tailed, they are probably all Short-tailed. Anyway, it's unlikely that two different species will appear within 2 days of one another.

Good luck on the Seabird trip tomorrow. At least we know there are now shearwaters in HK waters.

Title: Re: Short-tailed Shearwater
Post by Paul Leader on Apr 26^th, 2006, 9:08am

Geoff,

I think your first photo is of a petrel and not a shearwater. The wing itself and the wing proportions look rather short, and in conjucntion the tail looks rather long. However (and not surprisingly) the photos are rather blurred so it is difficult to be completely sure, but I think your first id of Bulwer's is proably correct.

The others would all appear to be Short-tailed Shearwater; pwehaps this is a regular passage migrant?

Title: Re: Short-tailed Shearwater
Post by geoff_welch on Apr 26^th, 2006, 1:09pm

Thanks Paul.

Let me explain the conditions under which I saw my bird. I started seawatching from the SE point of Po Toi on Sunday at 4.15pm. I recorded the conditions as SW wind strength 2/3, good visibility. So the wind was behind a bird moving NE.
At 4.30pm, I saw a mid-brown coloured shearwater with white underwing very similar to the second set of my photos - presumably Short-tailed. My other bird came along at 6pm. The light conditions were still good, with the sunlight to the bird's right. My first impressions were black, shearwater and small. My next thought was to photograph. So I spent most of the rest of the time viewing the bird through my camera viewfinder and concentrating on the photos. Unfortunately, the EOS autofocus system is not very good over the sea, the net result was as you see, fairly blurred images.

So, I am left with my first impressions and some blurry photos. The bird seemwd all black with no white under the wings. My only recollection of the bird's flight was direct, low with no irregular movements. I attach all the useful photos from those I took.

http://www.geocities.com/geoffwelch46/s1.jpghttp://www.geocities.com/geoffwelch46/s2.jpghttp://www.geocities.com/geoffwelch46/s3.jpghttp://www.geocities.com/geoffwelch46/s4.jpghttp://www.geocities.com/geoffwelch46/s5.jpg
http://www.geocities.com/geoffwelch46/s6.jpghttp://www.geocities.com/geoffwelch46/s7.jpg

For your comment, or anyone else, particularly those who have seen Bulwer's Petrel.

Title: Re: Short-tailed Shearwater
Post by miket on Apr 26^th, 2006, 1:29pm

I've seen quite a lot of Bulwer's (hundreds certainly) in Madeira, the Canaries and in the Taiwan Strait, but frankly I don't see what you can do on the basis of the photos of this particular bird - when I said I believed all the birds in the photos were Short-tailed, I guess I was including that one by default really, and on the basis of probability, given that we've got reason to believe quite a few Short-taileds came well in to HK waters on Sunday at least.

It's really just a gut feeling but the overall jizz impression given to me by the extended set of pictures of the putative petrel is actually of a smallish shearwater, and not of a petrel, and I think the final close-up of the Short-tailed equally shows how petrel like a shearwater can look. And yet again in my experience, in strong wind conditions Bulwer's can initially suggest a small shearwater, due to their long wings and shearing flight action.

Not one we'll ever really be able to do anything with, I'd venture to suggest.

Mike Turnbull

Title: Re: Short-tailed Shearwater
Post by Paul Leader on Apr 26^th, 2006, 1:53pm

Having seen a larger collection of photos of this bird I am less inclined to believe it was a petrel. It is probably a small shearwater as Mike T states, but I also agree with him in that this is probably one that will not be resolvable.

Title: Re: Short-tailed Shearwater
Post by geoff_welch on Apr 26^th, 2006, 4:14pm

OK, I'm happy with that. I've now converted to manual focus on photos over the sea. Much slower and more difficult, but more reliable.

Title: Re: Short-tailed Shearwater
Post by John Holmes on Apr 26^th, 2006, 11:06pm

Some Shearwater shots taken this afternoon (April 26, 2006) at south of Po Toi Island.
Good company, interesting birds!

Pics 6 and 7 may be a different individual

http://www.hkbws.org.hk/fileServer/PhotoG/jemi/jjh/hk_060426_01.JPG

http://www.hkbws.org.hk/fileServer/PhotoG/jemi/jjh/hk_060426_02.JPG

http://www.hkbws.org.hk/fileServer/PhotoG/jemi/jjh/hk_060426_03.JPG

http://www.hkbws.org.hk/fileServer/PhotoG/jemi/jjh/hk_060426_04.JPG

http://www.hkbws.org.hk/fileServer/PhotoG/jemi/jjh/hk_060426_05.JPG

http://www.hkbws.org.hk/fileServer/PhotoG/jemi/jjh/hk_060426_06.JPG

http://www.hkbws.org.hk/fileServer/PhotoG/jemi/jjh/hk_060426_07.JPG