wgeoff

On Monday morning at 7.40am I was at my ususal seawatching spot with a mobile in my right hand speaking to my wife and my binoculars in my left hand, scanning the sea to make sure I didn't miss any Short-tailed Shearwaters (I had seen 8 already that morning). I spotted a dark seabird which I realised immediately was not a Short-tailed Shearwater because the flight was quite different.

I regret to say, I dropped the phone and spent the next minute observing the bird and taking a few photos, leaving my wife to talk to herself. She has since told me, she will forgive me provided I can prove the bird was worth it. So I need some real help here please.

First, the photos. These are all exactly as taken except I have magnified  them x2 to improve the visibility.

  

I originally thought this must be a Bulwers Petrel, mostly because of the last two photos, but once again I think I've got it wrong on size which I am hopeless at. This bird was about the same size as Short-tailed Shearwater which I can confirm by comparing photos taken at roughly the same range. I thought all shearwaters flew with stiff wings, whereas this flew with angled wings in a very lazy fashion, which I think fits with Wedge-tailed. Anyway, my description is

Apparently all dark seabird, appeared darker than most Short-tailed which are brown, this bird more black (the photos show some slight colour variations on the bird). Body less bulky than Short-tailed, lighter looking with long tapering tail end. Longer winged than Short-tailed, wings mostly angled at the elbow and wing-tips drooping, appearing to touch the water. Flight completely different to Short-tailed, flying very low over the sea, very leisurely with long gliding periods followed by a few slow leisurely wing flaps on loose wings, not stiff.

I suspect this description may fit a number of shearwaters but I have chosen Wedge-tailed because of the body shape. I am quite sure it was not Short-tailed. For comparison, I attach two photos from above in actual size, together with a Short-tailed.



[ Last edited by wgeoff at 18/08/2010 17:36 ]

lpaul

To be honest I am not sure that the photos are good enough to permit a reliable id.  That said, I would favour Bulwer's Petrel.  There appears to be an extensive paler area on the upperwing and the tail looks too thin and finely tapered.  In addtion Wedge-tailed typically flies with the carpal held well forward and the wing tip swept backwards.  The body also looks very slender and petrel-like.

wgeoff

Thanks Paul.

Here are comparitive photos of this bird and Short-tailed Shearwater taken about 15 minutes later at about the same range, maybe slightly further away, with the same lens.



According to my calculations, Bulwers should be two-thirds the size of Short-tailed. Maybe it's a camera issue or the Short-tailed is further away than I thought.

I agree, the whitish line across the wing on the first two photos is indicative of Bulwers. Also the first photo shows the wing length is 25% longer than the body which is correct for Bulwers but too long for Wedge-tailed (wing length and body should be about equal).

Anyone else have a comment?

[ Last edited by wgeoff at 18/08/2010 17:37 ]

tmichael

I think it looks very much like Bulwer's too, so I think you were right first time Geoff - it's a common bird in the Taiwan Strait and must occur here.

I agree with all the things Paul says about the shape, esp. re tapered rear end + it also seems to me typical of Bulwer's and very unusual for Wedge-tailed or most other shearwaters that it appears to be flying with its head above - as opposed to out in front of - its shoulders in some of the shots.

I accept, as Geoff clearly does the limitations of these photos, but I think you might find enough experienced observers to say this is Bulwer's from these photos - and there are species on the HK list without photos of any sort having been taken of course.

And finally, concerning size Bulwer's frequently looks bigger and longer-winged than you might expect, especially in shearing flight.

Mike Turnbull

wgeoff

Thanks Mike.

Since the first posting, I've had the opportunity to view a flight video clip of both Bulwers Petrel and Wedge-tailed Shearwater on BWPi.

It's obvious from the video clip that this bird is not a Wedge-tailed Shearwater, the whole shape of the wings and body in flight and the relative proportions of each are different, as both Paul and you have indicated above.

On the other hand, the Bulwers Petrel flight clip does fit my bird well, the body size, shape, the wing length and the leisurely flight.

The video clip has a freeze frame option and by using this often enough on the Bulwers Petrel flight clip, I have been able to find a freeze frame which is very close to many of the photos. In particular, some features that didn't strike me at first - in the first of the following photos, how the wing tips bend down at almost 90 degrees to the rest of the wing which is almost horizontal, and in the second photo, how the inner leading edge of the wing bends sharply backwards at the carpal joint, something I thought was a photo error before.



Unfortunately, I can't reproduce the BWPi images here.

I was seawatching at the same place again yesterday, only this time in good visibility, and it's clear the bird was closer to me than I had previously thought, the mist at the time prevented me from getting a true appreciation which might help explain my error on size.

So, I have now come to the conclusion this bird was a Bulwers Petrel and will submit it as such for critical examination. Hopefully, my wife will accept it.

Whether the Rarities Committee will also accept it I don't know, but that's not so important at the moment.

[ Last edited by wgeoff at 18/08/2010 17:38 ]

kmike

Hi Geoff

having never seen Wedge-tailed Shearwater or Bulwer's Petrel Ihad nothing to contribute, bt it has been fascinating to follow the reasoning process, especially with the comparative pix you have posted.

best of luck with your submission for yet another Po Toi First.

Cheers
Mike

PS Is this a "Champagne Bird" for anyone? . . .and who decides whether it is - Graham or the Records Committee. Since neither saw the bird I'm not sure the chances are too high on either count . . .

wgeoff

Thanks Mike

I have had some time this week to look at these photos in more detail.

Because the bird is dark and the sea is light, by increasing the contrast between dark and light on the actual photos above, I am able to get a much clearer outline shape for the bird, as here.

The head, body, tail and wing shape and relative size of the wings vs the body compare well with a copy of an actual Bulwer's Petrel photograph on the right for comparison




[ Last edited by wgeoff at 18/08/2010 17:39 ]

cmichaell

Hi Geoff,

Have just returned from two weeks enjoying seabirds in Galapagos and Peru [amazing - happy to pass on details to anyone interested] and thus join this debate late in the day after the key issues have been identified [especially the constructive comments from Paul and Mike, and your own further analysis].

I fully agree that the bird is definitely not a Wedge-tailed Shearwater and further agree that in the context of Hong Kong it is most probably a Bulwer's Petrel.

I have seen a good number of Wedge-tailed Shearwaters in Australia on several visits and refreshed my jizz on a recent pelagic out of Wollongong earlier this year when good numbers of Short-tailed and Wedge-tailed passed close to the boat.  Compared to Short-tailed, Wedge-tailed is significantly larger and heavier with broader-based wings and a more powerful but languid flight style compared to the more frantic flight of Short-tailed. Whilst I agree with you that sizing an isolated seabird can be difficult, the jizz is conclusive. The wings are far too narrow and too long in relation to the body length, and the head and bill far too small with too little projection in front of the wings not just for Wedge-tailed Shearwater but for any shearwater.

However, all these features are spot on for a petrel. Most of your photos show clearly the small head and indicate a small bill, and the last two show in addition the wing shape and wing/tail ratio. Your description of the flight style being lazy with long glides on angled wings is again dead right for a petrel in light wind conditions.

The bird appears all dark [other than the paler upperwing bar which you refer to but which I cannot see clearly] which fits Bulwers [although dark phase Wedge-tailed Shearwaters can also show paler upperwing bars but are eliminated on jizz].

The last issue is whether there are any confusion species. The slightly larger but similar West Indian Ocean Jouanin's Petrel is a possibility but highly unlikely compared to Bulwers which is known to breed in South and East China Seas and expected to return from the south to its breeding areas in late April and May.  Other possible dark petrels are generally larger and heavier with heavier heads and bills and broader wings.

So there it is,  a good candidate for Bulwer's Petrel. Well done again for spotting the difference, getting the photos and triggering the debate,

Mike

PS I declare my interest in Graham's Champagne competition, but assure you this has not biased my views!!

tbob

You will find videos of the Wedge-tailed Shearwater at  

http://www.hbw.com/ibc/

wgeoff

Thanks Mike.

It was quite easy to say what the bird was NOT (Short-tailed Shearwater), from the flight alone. But much more difficult to say what the bird was, for me at least . Fortunately, various people came to my assistance and I am now confident of the ID as Bulwer's Petrel.

One of the issues with taking photos of a flying bird is, you don't really get time to look at the bird. But for me, the photo is much better - I can see many things that my eyes did not pick up. Also other people can see - a picture is worth a thousand words. None of my rare Po Toi birds would have even been discussed without the photos - and probably quite rightly!

Thanks also Bob - a very good website for videos. There is a video of a Bulwer's Petrel but the bird stubbornly refuses to fly on my computer, I expect this is why the video gets such poor marks.