Tuesday, September 23, 2008

19th September 2008: Tanjung Tokong, Penang, Part 3: Sandpipers and stints and other stuff

As the tide came up a nice selection of waders congregated on the nearby sandspit.

Calidrid collection. I managed to get these four Calidris sandpipers to pose photogenically - largest at the back, smallest at the front! Ignoring the partially obscured birds, they are Great Knot, Curlew Sandpiper, Broad-billed Sandpiper and Red-necked Stint.

This pic of adult Curlew and Broad-billed Sandpipers nicely illustrates the difference in bill and leg length.

Curlew sandpipers stand out in flight due to their (mostly) white rump. Here are two with a Broad-billed and a couple of Red-necked Stints.

Actually, I hadn't realized till today that, at least in worn breeding plumage, Curlew Sandpipers can have quite extensive dark spotting on the rump and uppertail coverts. The left hand bird even seems to have the faint beginnings of a central rump stripe, more typical of other small calidrids.

I didn't see any Little Stints today, but I was pleased to see some Little-like Red-neckeds. Here. the left hand bird seemed a little more 'leggy' than its colleagues. The consistency of the leg length as it fed suggested the length was actual rather than subject to posture.

Another Red-necked that appeared to have quite a well-streaked breast - at least the sides. The dark feather shafts on the rear flank, the short tarsus and short, straight, tubular bill are all typical of Red-necked however.

A more typical and obvious adult Red-necked Stint.

My first juvenile Red-necked of the season. I was surprised to see that it was pretty worn; the buff edges and white tips to the scapulars have already largely worn away.

High tide is often the time when waders will seek out some fresh or brackish water to spruce up their plumage.

Just above the tail is the uropygial gland, which secretes an oil that the bird uses to waterproof its feathers. First it smears the oil over the bill tip.

Then it applies the oil to the feathers by rubbing them with the bill. More pics of waders and their uropygial glands can be found here.

Here's a close-up of the tail. The legendary paper on the Identification of Peeps and Stints by Grant and Jonsson gives one of the 'in-hand' criteria for separating juvenile Little and Red-necked Stints as the pattern of the pale fringe on the central pair of tail feathers. On Red-necked, if it is present at all, the fringe is confined to the outer web. The dark feather-centre is rounded at the tip.

On Little, the equivalent pair of tail feathers, viewable here, have an obvious pale or rufous fringe on both webs at the tips of the feathers. The dark feather-centre typically breaks the fringe at the tip as a sharp point.Hmm! There's something I didn't know before!

Something simpler - a juvenile Common Sandpiper creeping up on dinner!

A couple of pics to finish off showing the expansion of the roost as the tide came up.

Monday, September 22, 2008

19th September 2008: Tanjung Tokong, Penang, Part 2: Plovers

As usual, Lesser Sand Plovers were the commonest wader on the mudflats, and, as usual, they were aggressively defending feeding territories. Once again, the adults seemed to dominate the juveniles.

Here's a 1st winter plumaged bird, nicely illustrating the fact that juveniles undergo a body but not a wing moult. Hence the body feathers are plain and adult-like, while the wing and tail feathers show the broad pale fringes distinctive of juveniles.

This adult is interesting; the bill looks significantly shorter and differently shaped from the 1st winter, which shows the long bill typical of the 'schaeferi' race. Could this be 'atrifrons'?

I had a good chance to observe a couple of feeding Greater Sand Plovers. This is an adult...

...while this is a 1st winter. The pale fringes on the wings have largely worn away on this bird.

These two were much more tolerant of each other than Lesser Sand Plovers would be.

Nevertheless, there was some tension, as could be seen by the two birds exchanging insults!

I was intrigued to see that both birds had serrated cutting edges to their upper mandibles - presumably to help them keep a hold of wriggling crabs.

Eventually the altercation became physical, and surprisingly, the young bird chased off the adult, which retreated to a safe distance.

So the young bird won this particular 'turf war'.

A couple of shots showing Greater and Lesser Sand Plovers in flight. I've read that the longer toe projection beyond the tail is a useful id feature of Greater, but in the field I've never found it to be of any practical use. The head and bill structure are still the clearest ways to separate the two for me. In the top picture, the Greater Sand is on the right, and in the lower one there is a lone Lesser bottom left.

Welcome back! Away on the tideline I noticed a single "White-faced" Plover. It has arrived almost a month earlier than my previous earliest record. Just as in October 2006, when I first noticed the odd pale birds, the "White-faced" has turned up with a 'normal' Kentish Plover. A Greater Sand Plover provides a size comparison.

The white-fringed coverts, short lateral breast patches, white lores and lower ear coverts and pale legs are what set these birds apart from typical Kentish Plovers.

The faint band across the forecrown, and gingery rear crown and ear coverts, together with the mostly white lores, make me think this bird is probably an adult male in fresh non-breeding plumage. Hopefully more will arrive over the coming weeks.

Sunday, September 21, 2008

19th September 2008: Tanjung Tokong, Penang, Part 1: Whimbrels

The tide was perfect for photographing waders this afternoon, and as a result I took just under a thousand pics. Yikes! I think the best way to approach putting the best ones here is to split it into a few posts.

This first one will be dedicated to the antics of a Whimbrel.

This adult flew in on the rising tide and began to very gently probe crab holes.

It inserted its bill incredibly slowly and carefully...

... just like a heron stalking a fish.

Here's the moment when, with a swift jerk of the head, it seized the crab.

Et voila!

You can see this sequence animated here.

As I've seen Common Sandpiper do in similar fashion, the Whimbrel then spent some time shaking most of the legs off the unfortunate crab...

... till there were only a couple left.

I suppose swallowing a live crab legs and all might cause a bit of indigestion!

After dinner it was a short walk to the nearest watering hole...

A quick drink to chase the crab down. Waders almost always do this after swallowing large prey.

And then time for a wash and brush-up.

The arrival of two fresh juveniles in the adult's feeding territory provoked this odd threat display. To me this pose looked rather passive, but it was to lead to something much more aggressive.

New kid on the block - beautiful fresh juvenile feathers - but not very streetwise!

The adult spread its tail and rump feathers and began to utter a bubbling, curlew-like call.

It then slowly got to its feet, flashing its rump and tail toward the further of the two birds, still calling.

Picking up speed, taking a line diagonally past the intruder, it suddenly spread its wings and tail, tilting toward the juvenile to maximize the effect of the pale rump flash.

This proved too much for the juvenile, and it flew off. Even this Red-necked Stint had to jump out of the way!

It then turned its attention to the nearer bird, still calling and fluffing out its rump feathers.

The juv decides its time to leave!

This fella isn't messing around!

A final shake of victory!

The last I saw of the juveniles.