Tuesday, August 05, 2008

5th August, 2008: Tanjung Tokong

I've been drawing waders a lot lately so I though it was time I went to look at some real ones! This was my first visit to Tanjung Tokong of the autumn, and for several months.

Overall, I was quite pleased by what I saw. The mangroves are developing nicely, screening the mudflats more effectively from the shore, and the mudflats themselves have accreted considerably. Construction at the site seems to have finished for the time being, so, although there are workers around, and fishermen, overall disturbance levels may be lower than in spring.

Of course, one thing never gets better, and that's the amount of rubbish and pollution! That's because the same current that carries the silt to this corner of the bay also carries everything else dumped into it. It's really sad to see waders trying to find food in all that junk. But at least there were waders. Not many - maybe 30 - but it's a start, and hopefully a positive sign of what's to come.

Andy Adcock asked me if I'd noticed which sex turns up first, as apparently males leave the breeding grounds earlier than females. So I tried to differentiate sexes today.

I don't have much literature available on distinguishing males from females, but generally, males are slightly smaller and shorter-billed than females. In the case of Curlew Sandpipers, I think that males show less barring on the flanks than females. So I reckon the two birds that were present today should be males. Thanks for asking Andy!

Regardless of gender, these birds have started their head and underbody moult (see the fresh crown and nape feathers and the white breast feathers pushing through the red). They will eventually complete a full body and wing moult, but at the moment all the wing, scapular and mantle feathers are still the old, worn breeding feathers. Note how the pale fringes are very worn, and the appearance of the feathers is very ragged.

A small flock of Lesser Sand Plovers came in as the tide rose, still largely in breeding dress.

There were two distinct plumages - some black-masked birds and others that were generally less well-marked. I wondered if the less showy birds could be females.

This appears to be confirmed by my very unscientific attempt at comparing bill length and depth! I took three photos of different individuals of both types, as much as possible in side-on profile. I sized the photos approximately by trying to make the eye as near as possible the same size in each photo. It's difficult to be exact in the case of the black-masked birds. Overall, I would say that the duller, browner birds show noticeable longer and more massive bills than the black-masked birds, so I'm designating them females till someone puts me right!

As mentioned in previous posts, these Lesser Sand Plovers are of the 'schaeferi' race, which is one of three races, known collectively as the 'atrifrons' group, which breed in eastern Tibet, well south and west of the 'mongolus' group - two races which breed in North-eastern Siberia. These southern birds are characterized by relatively long bills (the longest of any race of Lesser Sand Plover) and largely black foreheads in breeding plumage. Short-billed 'mongolus'-type Lesser Sand Plovers (or Mongolian Plovers!) migrate further east than the Peninsula down as far as Australia, and are probably a rare visitor here. I think I saw one in April at Kapar (see this pic and compare the bill structure with these birds). There are some superb pics of 'mongolus' Lesser Sand Plovers here.

The difference between the worn, old breeding feathers and the fresh non-breeding ones is clearly visible here. Four rear scapulars, some mantle and rear crown feathers are new - darker, smoother, with a neater shape, compared to the old coverts, primaries and tertials - bleached and worn, some with an obvious central shaft spike.

Sand Plovers hold 'hunting territories' on the mudflats, and will defend their 'personal space' vigorously against intruders. Their foraging strategy, using eyes and ears to locate prey, is different from sandpipers, which often forage in groups, probing the mud with their bills. This bird has just either spotted or heard a polychaete worm near the surface of the mud. It quickly runs forward...

...grabs and pulls ...

...and PULLS!...

You can see the upward pointing barbs along the worm's body, which help to anchor it into the mud, and make pulling it out hard work!

Suddenly the worm pops out; it always amazes how the bird manages to keep from falling over backwards at this point! Click here for the animated version!

It becomes obvious why keeping one's distance from neighbouring birds is wise! A male comes rushing in with piratical intentions...

...allowing the catcher no time to enjoy her meal - it has to be slurped down spaghetti-style as fast as possible!

Go find your own worm mate!

One way of distinguishing Greater from Lesser Sand Plover in breeding plumage is that, supposedly, only Greater shows any chestnut on the upperparts. However, as this picture shows, this only holds true in spring, when the plumage is fresh. By now, Lessers can also show strong chestnut tones on the scapulars.

The Keith Vinicombe article I referred to in the last post states that "Greater [Sand Plover]moults out of summer plumage before it migrates and Lesser afterwards, so a summer-plumaged sand plover in July or August should prove to be a Lesser." This was more or less the case with the 3 or 4 adult Greater Sand Plovers present.

This bird is definitely further forward in the moult cycle than the Lesser Sand Plovers, having moulted most of the head and breast area. However, most of the upperparts feathers are still unmoulted. A few nice fresh white-edged median and lesser coverts are appearing.

Here's the same bird above the longest-billed of the female Lessers for comparison. The bill shape is quite similar on these two birds (Lesser is usually blunter-tipped). Note the difference headshape (more angular on Greater, rounder on Lesser) and position of the eye (more central on Greater, further forward on Lesser). These differences are difficult to describe but quite distinctive with practice and reasonable range views.

This isn't the best comparison shot, but even here, it's possible to see the difference between the long, rakish, long-legged shape of the Greater and the smaller, dumpier, rounder lines of the Lesser.

A Greater roosting on the shoreline. No explanation for this one, except that I like the pose!

This was a reaction to House Crows buzzing the waders.

Surprise of the day for me was this juvenile Greater Sand Plover. My previous earliest juv was over a month later than this! Must have been one of the early hatchers. One key to ageing waders is the wing coverts, since juveniles of most species won't do a full wing moult till next autumn. Juvs generally show more highly patterned coverts than adults. This bird has already begun its first body moult (see the slightly greyer feathers in the outer mantle, and one or two scapulars).

Notice that the primaries are visible beyond the tertials of this juvenile (the black feathers that look like the tail), whereas on the adult (see above), the primaries are invisible. Juvenile tertials are generally quite a bit shorter than adult ones, so this has to be taken into account when comparing wing lengths of different birds.

One of the Red-necked Stints was still in nice colours. The mudskippers in the background reminded me of the slugs in the movie 'Flushed Away' singing 'Poor old Roddy, flushed down his own potty'!

Those stray dark-shafted feathers on the flanks and lower breast (sometimes extending down to the vent) are a surefire way to distinguish Red-necked from Little Stint, as the latter never shows them, as far as I am aware.

The stint finds a prey item - don't know what it is exactly.

...picks it up...

...and tries to swallow it.

..but it's too large, or too sandy, so it does what waders often do when they catch large prey ...

...takes it to the water to give it a wash first.

Unfortunately, the bird then went and hid behind Christiano Ronaldo, so I wasn't able to capture it eating!

Last bird of the day was this Common Sandpiper roosting on a fallen coconut palm. Looking forward to the next few months!


Unknown said...

Nice one Dave! I went to Gurney drive on Saturday but didn't see any roost. Just great n little egret.

Jason Bugay Reyes said...

very informative dave. hope can get closer look of lesser and greater sand plover in my place tomorrow :)