Tuesday, October 28, 2008

24th October 2008, Lok Kawi Beach, KK, Sabah

During the Wader Workshop we had several opportunities to watch some species which are rare or unusual in the Peninsula, such as Grey-tailed Tattler, Chinese Egret and Common Ringed Plover. On my last afternoon I wanted to try to photograph these birds if possible, so headed back to Lok Kawi beach. Unfortunately the weather was against me, as the skies got darker and darker, eventually culminating in a downpour that would last 12 hours or more. The pics below are a combination of some taken on 19th Oct (in perfect early morning sunlight) and the 24th (in miserable light and weather). You'll easily spot which is which!

Here's a nice adult Grey-tailed Tattler. This was the commonest 'sandpiper' during our wader workshop, making a nice change from Redshanks!

Grey-tailed Tattlers are extremely similar in non-breeding plumage to Wandering Tattlers, which, however, follow a much more easterly migration route, and have never been recorded in Borneo or South-east Asia.

Just for the record, Grey-tailed may be told from Wandering, according to the books, by:

1. Grey-brown rather than dark slate upperparts - check.
2. Primary tips falling level with tail as opposed to extending beyond tail - check.
3. Nasal groove barely half bill length, as opposed to extending well beyond mid-point - hmm - this seems rather longer than half way along.
4. Supercilium extends some way behind eye, as opposed to stopping at eye - OK.
5. Largely white rear flanks, as opposed to slate grey rear flanks - check.
6. Should show 3-4 primary tips beyond tertials, as opposed to 4-5 - I can barely make out 2 primary tips beyond the tertials on this bird - but then the outer primaries are unmoulted and worn.
7. Call should be a rising "tu-eet", or a soft "tuu tuu tuu" anxiety call, as opposed to a "plaintive rippling trill of 6-10 'pu-tu-tu-tu-tu-tu-tu' notes, like a subdued Whimbrel". This bird gave a soft 'wee-wee-weep' call when taking flight.

These flight shots show the wing moult more clearly. The outer three primaries and inner three secondaries are worn and unmoulted, while the remainder of the flight feathers have been recently replaced. Primary moult goes from the innermost to the outermost, while secondary moult travels in the opposite direction.

Here's a juvenile bird moulting into first winter plumage. The white-flecked wing coverts and scapulars are worn juvenile feathers. Notice how much smaller juvenile feathers are than adults', especially scapulars and tertials. As a consequence of the tertials being smaller, 5 primary tips fall beyond the tip of the tertials - whoops, that shouldn't happen according to the books! Those pale-tipped upper tail coverts are another good pointer for Grey-tailed though.

Not sure how good a field feature this is, but I noticed that the tattlers would always raise their wings momentarily on landing.

From one tricky pair to another - the sand plovers. On the deck, they're not too difficult when seen close up. Here's a Greater in front with a Lesser behind.

But what about in flight?

Again, according to the books, Greater (the top bird in this composite):

1. Has a longer toe projection beyond the tail tip - err - nope!
2. A less prominent white wing bar across the inner wing - no again.
3. The wingbar 'bulges' more on the inner primaries - can't see it myself.
4. The tail has a dark subterminal bar - wellll - maybe...
5. Shows more white on the tip and sides of the tail - possibly, but marginal!

This one shows a Greater on the left. The toes project fractionally longer beyond the tail on this bird, but you'd be doing well to be sure of the difference in the field.

The Greater is again on the left here. Maybe the Lesser shows a clearer white secondary bar, but it seems to me that if you are getting good enough views to judge things like toe projection, wingbar shape and strength, etc, you'd be better off looking at the bill proportions, which, to my mind, are the easiest way to tell the birds apart. I also think that Greater shows a more rakish body shape, with more 'tail' behind the wings and 'head' in front of the wings than Lesser.

Ah - this is a bit easier! A Pacific Golden Plover in front of a Lesser Sand Plover.

Moving from waders to egrets - these Little Egrets look like a stop-motion picture as they come into roost at high tide.

One of my goals for this trip was to be able to see white morph Pacific Reef Egret, and to be able to compare it with Chinese Egret. Despite the rarity of Chinese globally, I have seen far fewer white morph Pacific Reef than Chinese. For some reason, the white morph is much rarer than the grey morph, and seems to be commoner in areas where sandy beaches predominate.

We saw several of these grey morph birds, but this particular one was paired with a white morph!

Very nice!

It still had most of its breeding plumes, as this pictures shows.

From time to time, it would launch itself into deeper water,

hovering or treading water...

...before diving in after its prey!

We saw several Chinese Egrets during the workshop, when I didn't have the camera with me! In the last few hours of daylight on my last day, I was determined to track one down to get some comparison photos with the white morph Pacific Reef. I managed it, though the light conditions weren't the best!

Photographed from under an umbrella!

I would recommend a read of this paper on separating Chinese from white morph Pacific Reef Egret, published in the OBC bulletin a few years ago. I would say that it is a pretty accurate summary of the key differences.

In all the following composites, Pacific Reef is above and Chinese below. Pacific Reef looks a much 'better fed' and well-built bird compared to the rather 'skinny' Chinese. The differences in bill proportions and leg, especially tarsus, length are also obvious here.

Even at a distance these differences are fairly obvious, though somewhat subjective. This particular Pacific Reef had bright orange soles to the feet, while all the Chinese seen had greenish-yellow soles. Notice also the Pacific Reef Egret's thick tibio-tarsal joints.

Bare part colouration may be variable according to season and individual, although Chinese in the non-breeding season do seem to show a fairly consistent bill pattern - largely yellow lower mandible and a yellow cutting edge of the base of the upper mandible.

But the bill structure and shape of the loral skin make for two very different-looking birds. The loral skin of Pacific Reef is very deep (top to bottom) and seems to go over the forehead. Below the eye, it extends in a quite obtusely angled triangle, whereas the same area is smaller and rounder on Chinese. The top line of the loral skin can be quite similar at certain angles, though Chinese has a more pronounced dip just in front of the eye.

Pacific Reef's bill is broad-based, tapering gradually to the tip, which is rather blunt, with the upper mandible overlapping the lower slightly. Chinese has a thinner, more parallel-sided bill that ends in a sharp, dagger-like point.

Chinese has quite a pronounced peak at the rear of the crown, whereas Pacific Reef's headshape is more flat-crowned.

The tarsus of Pacific Reef seems thick and short, while on Chinese Egret it seems better proportioned with the rest of the body.

The subtle differences in loral skin and bill shape described above, in combination, create two very different 'face patterns'.

The lower picture of the Chinese Egret was one of the last I took before the heavens truly opened on my last evening in Sabah. It was a memorable trip for me. Thanks to everyone who helped organize and who took part in the Wader Workshop. I hope it was as worthwhile an experience for you as it was for me!

1 comment:

Mark Young said...

I liked your write-up on the Waders. Interesting to see what species you have locally compared with what we get, as well as seeing the differing plummage stages.