Monday, May 17, 2010

16th May 2010: At sea off Tanjung Dawai, Kedah

Choo Eng and Terence tempted me back to sea yesterday with tales of chum aplenty! Not till later did we discover that deep frozen chum doesn't thaw sufficiently in tropical sea within one day! So - good tip - don't deep freeze chum!

Anyway, it didn't make much difference. The boat only stopped once today and gave up by four o'clock due to lack of fish. Lack of fish, but luckily for us, no lack of birds!



The day was dominated by Short-tailed Shearwaters again - we had 21 sightings despite the shorter than usual day.



Sightings were clustered about 15-20km offshore along a line that roughly corresponded with the edge of deeper water, and not far from the islands of Telor and Songsong. We went out much further than this but there were no shearwater sightings further out.



Compared to just less than a week ago, the birds seemed to have 'learned the drill.' As soon as our net was cast, two birds made an appearance, flying in and settling near the perimeter of the net.



This gives an idea of the size compared to Bridled Tern.



The birds spent time diving for fish, often surfacing with wings half-opened.



You've heard of the song "Flying without wings" - this is the shearwater version - "Wings without flying!"





As the nets were winched in, the birds came closer and closer. Sadly for photography, they were always against the sun.



They got quite close!





According to Onley and Scofield, the "majority of the population apparently flies [from southern Australia] to waters off Japan in June, the Bering Sea in July, and on to the central Pacific during August on their way south again." All of which begs the question - what are these birds doing here, and where will they go after they leave?

They clearly aren't 'out of range' vagrants - they occur each year in varying numbers. They seem to have begun a body moult and their wings are heavily worn. Will they move up into the Bay of Bengal to complete their moult there? Circle back down into the Indian Ocean? Perform an unlikely overland crossing over the relatively narrow landmass of the Isthmus of Kra? Or retrace their journey down through the Straits of Malacca and move into the South China Sea? How little we still know about seabirds!






This bird gives a good impression of the state of plumage of the birds we saw.









It was intriguing to see the variation in underwing colouration, and the effects of different lighting conditions!



An odd variation - this bird showed pale tips to the coverts and appeared to have fresh secondaries and a few inner primaries, yet most of the primaries and humerals were very worn. Perhaps it was in suspended moult.

Apart from shearwaters, it was a good day for terns. Apart from the ubiquitous Bridled, there were good numbers of Common and White-winged Terns still about, as well as one or two Black-naped.



I was quite surprised to see this Aleutian Tern - a new 'latest date' for birds in spring.



This photo gives a good view of the diagnostic features of the species - the broad white frontal triangle, dainty black bill, dusky grey upper and underparts creating a strong contrast with the white rump and tail, and blackish bar across the underside of the secondaries. The short-necked, compact jizz is also subtly distinctive, as is the fact that they usually fly looking straight ahead, rather than down at the water.





A couple of heavy-set, 'necky' Common Terns for comparison.



Unlike all the previous Aleutians I've seen from the boat,which have been brief fly-overs, this one actually came to the net...





...twice! Still, it never came close, and the poor light ensured that my pics didn't come out as well as I would have hoped.





Just after the Aleutian, and while still looking for it, I glimpsed a very pale tern that didn't strike me as Black-naped. I yelled 'Roseate!' and grabbed a couple of shots (the first a beautifully sharp one of the water behind the bird!) before it disappeared out of sight behind the the boat. The bird never appeared again, and I convinced myself that I had probably jumped to the wrong conclusions. However, close examination of my dreadful pics reveal that I was right! You can just about make out the pinkish flush to the underparts, and the distinctive pale upperwing, white trailing to the wing, darker wingtip limited to the outer three primaries, and the long, white-edged outer tail feathers. Had I not managed to get the photos I would undoubtedly have written off this bird - that's the joy of digital photography! Roseates breed on the east coast but are a rare bird indeed on the west.






















One good tern deserves another ... and another! Not long after the Roseate, this beauty turned up - a cracking Lesser Crested Tern - my second sighting from the boat.




Unlike the Aleutian and the Roseate, this one was eager to please!







Looking like a giant Little Tern!



There are fewer jaegers around now (presumably they time their migration to coincide with that of the terns), but there were still one or two around. This one was close enough to be identified as a subadult Long-tailed, and another two went unidentified.



It's pretty easy to tell a jaeger from a shearwater on the sea, even at quite a distance. Jaegers look like bananas, turned up at each end, an effect caused by the long neck and the angle of the wings and tail. Shearwaters are much flatter in the water, with a short neck, domed, duck-like head, and stumpy rear end.



The only jaeger species I'd recorded before today from the boat were Pomarine and Long-tailed, but I've always been on the look out for the elusive third species that makes up the 'set' - Parasitic (I grew up calling these Arctic Skuas and 'Parasitic Jaeger' still sticks sideways in my throat when I say it, but you have to move with the times I guess!). Anyway, back to this bird. It looked promising. It was clearly too bulky to be a Long-tailed, and 'Poms' are usually extremely wary of the boat, unlike this bird.



Though an adult, the bird did not have well-developed central tail feathers, making things a little more challenging! However, the tips of what could be seen of the central tail feathers were sharply pointed rather than rounded, which favoured Parasitic.



This picture shows the wings looking rather narrower-based than a typcial Pomarine.



























On taking off, the bird attacked a tern, and then returned to the water to consume its ill-gotten gains. It did this three times. Long-tailed often harass terns, but I've never seen a Pomarine do so. The central tail feathers again look good for Arctic in these pictures.



In fact, the pale patch above the bill is a diagnostic feature of adult breeding plumaged Parasitic Jaeger. On Pomarine the black colouration of the crown extends down to the chin, encircling the bill base. The pointed central tail feathers can clearly be seen here.



Here's a composite of the three jaeger species in adult breeding plumage, all taken from the boat - Pomarine (top), Parasitic (centre) and Long-tailed (bottom).

3 comments:

Ben Lascelles said...

great stuff, very interesting to hear about these sightings and the pelagic trips your undertaking. I'd be interested to hear of any previous trips you've made, or have planned for the future, as Birdlife is trying to get some marine IBA projects underway in SE Asia. perhaps you can email me at ben.lascelles@birdlife.org?
best wishes
Ben

madibirder said...

Hi Dave,
Great inflight shots and so many species in one trip. Congrats.

Stu said...

Some briliant BIF shots there esp the terns. I saw 000's of Short taileds last month but not a single one came close enough for a decent shot......