Sunday, March 14, 2010

13th March 2010: Pulau Burung, mainland Penang

I was at the Red-throated Thrush site at dawn to see what would hop up onto the dead trees.

The first thing to attract my attention was a group of three Asian Koels, one of which was holding a feather. No idea what they were up to!

Next up was a preening Lineated Barbet.

Then I spotted a Banded Woodpecker sunning itself at the top of a dead tree.

Later on it went down the trunk and started excavating a hole.

A Dollarbird was an interested bystander!

Along the coastal bund, the female Common Kingfisher had successfully caught...something - not sure what.

Being a Saturday morning, the Landfill site was fairly crawling with bird photographers in cars. I went past one carload photographing White-browed Crakes and a Lesser Whistling-Duck with ducklings - hope they got some nice pics!

Even though they are a common bird, I couldn't ignore the Blue-tailed Bee-eaters in the golden early morning light. Stunning!

There are so many birds at Pulau Burung, and they are very habituated to people in cars, with the result that you sometimes encounter an unusual problem for photography - bird too close! This Slaty-breasted Rail was a good example.

The same was true of snipes. I was very keen to photograph some, but they were mainly on the grass verge besiede the road, and so flushed before I realized they were there. At last though, I got lucky.

A Pintail/Swinhoe's feeding out in the open only metres away!

The dull buff edge on both sides of the lower scapulars, and the barred median coverts showed that this was one of the Pintail/Swinhoe's pair, and not a Common Snipe. The problem was, which one?!

The large, squarish head, with the eye set well back favoured Swinhoe's, as did the thickish yellow legs (covered with greyish grime), but I knew I would need to see the outer tail feathers to be able to identify the bird for certain.

This is a sketch of three snipe species' tails from Paul Leader and Geoff Carey's paper on the 'Identification of Pintail Snipe and Swinhoe's Snipe' from British Birds. The dark grey-filled feather is (roughly) at the centre of the tail, so the picture shows only the left side fanned open.The blue-filled outer feathers are the important ones for identification. On Common Snipe, these are similar in breadth and shape to the other tail feathers. On Swinhoe's, the outer feathers become progressively narrower toward the outside, while on Pintail, the outer feathers become abruptly very narrow and pin-like, without much gradation from broad to narrow.

There are usually two chances to see snipe outer tail feathers in the field. One is when they engage in territorial disputes with other birds, when they will fan and raise their tails. The other is when they preen.

I watched this bird for over two hours, and it only preened the tail briefly twice in that time! This was the first occasion...

...And this was the second. On neither did the bird fully fan the tail. Nonetheless, on the first photo, you can see the tips of the undersides of many of the tail feathers.

The feathers on the left side appear to become gradually narrower, fitting the Swinhoe's pattern.

The second picture reveals that the tips of the upperside of the central tail feathers are white. Leader and Carey state, "The central rectrices of Swinhoe’s Snipe may also be conspicuously tipped pale, often white, unlike Pintail," so this seems to be another pro-Swinhoe's feature.

Although not useful for identification purposes, it was interesting to see that the tertials on either side of the bird were at different stages of moult. On the right side, the upper two tertials were new and still growing, while the lowermost one was old and retained very little patterning. On the left side, all the tertials were old and unmoulted.

A couple more pictures of the bird after it had climbed up onto the bund next to the road.

With the bird sitting so close to the road it was only a matter of time before it was flushed, so I had my sound recorder on in the hope of recording the flight call. When it was finally flushed, however, it was completely silent! Leader and Carey say that "When flushed, Swinhoe’s Snipe calls less frequently than Pintail Snipe, and a flushed snipe which is silent is most likely to be the former." However, I am always wary of arguing from silence!

The very short toe projection beyond the tail tip is another pro-Swinhoe's feature which Leader and Carey indicate might be valid. Check out the short toe projection on this vagrant Swinhoe's Snipe in Finland.

Another view of the outer tail on the bird in flight, though probably not conclusive on its own.

My four best shots of the tail!

Wells states that, on the evidence of the analysis of hunting-bags in the 1940s and 50s, Pintail Snipe is overwhelmingly the commonest of the three snipe species in the Peninsula (97 - 99+% of all shot birds analyzed were Pintail). This contrasts with my own admittedly meagre sample; all Pintail/Swinhoe's Snipes I have identified to species this season have been Swinhoe's. Wells suggests that one potential bias in the analysis results is the "partitioning of winter habitats between species, relative to those most often shot over," with the suggestion that Pintail prefers drier, harder substrates than Common and Swinhoe's. In the same way that hunters might prefer to shoot in drier habitats, birders tend to prefer birding in wetter habitats, or at least, it may be true that birds are easier to observe in the open when there is open water. Whatever the case, it may be dangerous to assume that Pintail/Swinhoe's Snipes are 'most likely to be Pintail' based simply on past data.


wondersf said...

A fruitful morning and very informative write-up. Thanks for your effort and sharing.

Wong Tsu Shi said...

Thanks for your effort in writing this informative piece on the Swintail Snipe.