Notes on Himalayan Swiftlets

It’s been almost 3 years since my last post! With the new social media culture, it has gotten more and more difficult to sit down and write something in length. I guess it’s about time I should do something with this blog to keep it alive and up to date. I decided that I would start with some notes on the “Himalayan Swiftlets” that I’ve photographed recently at several locations.

A classic look of Himalayan Swiftlet; note uniform dark underparts

Aerodramus swiftlets are definitely one of the most challenging groups of birds for identification. Most of the times, they can’t even be identified with certainty. In Thailand, there are 3 species of swiftlets within this genus; Germain’s Swiftlet (A. germani), Black-nest Swiftlet (A. maximus) and Himalayan Swiftlet (A. brevirostris). Traditionally, they could be identified based on habitat and distribution range with germani being found along coastal areas both on the eastern and western coasts, maximus being found only along the western coasts and brevirostris in non-coastal habitats mainly in northern and western parts of the country. However, with the booming of “swiftlet condos” built to harvest swiftlet nests, a very valuable product for the Chinese market, it seems that we can’t identify these birds based on habitat and distribution range anymore. Germain’s Swiftlet, a species which produces pure white nest, has already spread throughout the country with many swiftlet condos being built to attract it even in Chiang Rai, the northernmost province, and several places in the north-east, while the extent of range-expansion in Black-nest Swiftlet, a species which also produces edible nest but require some processing to filter the feathers out, is still largely unknown. Himalayan Swiftlet is the only species in Thailand which doesn’t produce edible nest and probably isn’t affected by the business in terms of range expansion. However, the confusing part is that there are 2 populations of Himalayan Swiftlets in Thailand; the resident rogersi and wintering brevirostris and probably innominatus.

Note dark unifrom underparts

From my observations in northern Thailand, the area where Germain’s Swiftlet has only known to colonise quite recently (within the last 10 years), I noticed that there are some differences in plumage colouration between Himalayan and Germain’s Swiftlet. On mountains higher than 1,500 m above sea level, a habitat where Germain’s Swiftlet is still not known to occur, I’ve noticed that all the swiftlets showed rather uniform dark greyish-brown plumage with not much contrast between upperparts and underparts unlike in Germain’s where the underparts are generally paler. Of course, this should be judged from similar angles and lighting conditions.

While rump patch is mentioned to be one of the main characteristics for identification, I find both Himalayan and Germain’s to have a wide range of variation from very pale to almost concolorous with the back. Lighting and angle can also greatly alter the paleness of rump patch too.

Possibly subspecies ‘brevirostris’; note very long and slender wings and long tail

Possibly subspecies ‘brevirostris’

Possibly subspecies ‘brevirostris’

Possibly subspecies ‘brevirostris’

Lastly, I’ve also noticed some variations among the structure of Himalayan Swiftlets seen and photographed in northern Thailand. Some birds seem to have very long and slender wings and longish tail making them look almost like Asian Palm Swifts. I think these birds are probably the wintering nominate brevirostris which is described to have longer wings than the resident rogersi. I usually see these long-winged birds at lower elevation and cultivated area mixing with other species including those that look like Germain’s Swiftlet, Asian Palm and House Swifts.

Possibly subspecies ‘rogersi’; note shorter wings and tail

Possibly subspecies ‘rogersi’

Possibly subspecies ‘rogersi’

Possibly subspecies ‘innominatus’; note concolourous upperparts with no apparent rump patch

Advertisements