On 17th August 2007, Ong Tun Pin sent an image of a curlew, commenting, “I have just come back from a 10 day trip to a very exotic island destination.
“Attached is a whimbrel-like wader that I hope you can guess as the name can be derived from one body feature shown in the picture (above). I know that wader is usually hard to id but this one has one famous body part that gives its name. Not found in Southeast Asia but at the edge of the oriental region.
“Would be nice if someone could tell me if this is a juvenile and whether it is in moulting. I was told that this bird becomes temporarily flightless during wing-moult. It was reluctant to fly and I was able to do some sort of wader ‘herding’ along the beach. But one still flew away after I have ‘cornered’ it at sand banks at 4 meters away. This is not the way we do wader-watching in Malaysia where often a combined effort of scoping 60x from far distance and lurking among tall grass still scares the waders away”
It was an image of a Bristle-thighed Curlew (Numenius tahitiensis), a rare bird whose breeding population is concentrated on the mountain tundra in West Alaska. It is called bristle-thighed because of the elongated feather shafts seen at the rear flanks and thighs (left). These long, shiny ‘bristles’ are usually seen only when the bird is handled. However, Tun Pin was fortunate to have captured this feature in his image, a feature he could not see through the lens. This again shows the importance of photographic images in the study of birds and bird behaviour.
The bird winters exclusively on oceanic islands, especially small Polynesian islands. And this was where Ong Tun Pin encountered the curlew, when he was on a ten-day holiday in Tahiti in August 2007.
This is a highly migratory bird, making long distance, non-stop flight of at least 4,000 km over the open ocean. The adults begin to leave their breeding grounds from early July, followed by the juveniles in early August. They meet at their staging grounds on central Yukon Delta before migrating to their winter grounds in the South Pacific islands.
The image above of the flying bird shows its chestnut rump without stripes. This is the diagnostic feature to separate it from Whimbrel (Numenius phaeopus).
In the wintering grounds, the bird moults and about 50% of the adults become flightless for about two weeks. This is the only shorebird known to have a flightless moult. This is not a problem where they winter in remote islands where there are no predators. However, when humans settle on these islands, the flightless moulting birds are at a serious handicap, especially with the introduction of domestic cats, dogs and even pigs.
The adults depart in early May while the immature birds spend all of their pre-breeding years on the wintering grounds.
Ong Tun Pin
1. Gils, van J. & Wiersma, P. (1996). [‘Family Scolopacidae (Sandpipers, Snipes and Phalaropes]. Pp. 444-533 in del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the birds of the world. Vol. 3. Hoatzin to Auks. Barcelona: Lynx Editions.
2. Kaufman, Kenn (1996). Lives of North American birds. Boston & New York: Houghton Mifflin Co.
3. Rosair, D. & Cottridge, D. (1995). Photographic guide to the waders of the world. London: Hamlyn.