Thursday, December 23, 2010

New Barn Swallow race in Borneo ?

Barn Swallow Hirundo rustica, occurs almost globally, is an abundant winter visitor to Borneo, recorded over all habitats from sea level to mountain peaks, and from offshore islands.

Some birds in Borneo during the winter months are in moulting plumage without their diagnostic long tail streamers, they can look similar to juvenile/immature birds in this plumage.

Here are some images of either moulting birds or juvenile birds, I am not sure, they may be all immature birds.
Here is how the adult should look like when not in moult, with its diagnostic breast-band and tail streamers.
The race usually recorded in Borneo is H. r. gutturalis, all the above birds should belong to this race, it occurs across China, Taiwan, Japan, Korea Kuril Island and lower Amur river.

H. r. tyleri,  another race which mainly breeds in South Central Siberia, Mongolia and North East China has been recorded in Myanmar, Thailand and Peninsular Malaysia. This race has dusky brick orange over its entire underparts compare to whitish or buffish underparts of the gutturalis race. This race has not been documented in Borneo as yet as it is not mentioned in Smythies, Mann, Phillipps and Myers in their respective publications.

The following bird photographed in Tawau is evidently from the race tyleri by virtue of its distinctive underparts coloring. It could be a regular visitor here, but due to its abundance, it could have been overlooked by most birders.
Edited to add: Thanks to Dave B., who raised the point on the races of satuata and  mandschurica. This might very well be the former, but the the two races might not be always separable.

Happy birding.


digdeep said...

Of these pink-bellied birds, Wells says:"Noticeably rufous birds are a small minority, and even these fall short of the rich chestnut of the subspecies 'tytleri'...Most pink/rufous birds match the white form on size, and are likely to belong in far-NE breeding populations 'saturata' and/or 'mandschurica'.

Wong Tsu Shi said...

Thanks Dave, points noted.