Paradise-flycatchers are among birders’ most favourite birds. Three species can be found in Thailand; 1) Blyth’s Paradise-flycatcher (Terpsiphone affinis), 2) Amur Paradise-flycatcher (T. incei), and 3) Japanese Paradise-flycatcher (T. atrocaudata). The male of Blyth’s and Amur Paradise-flycatcher can either have the typical rufous morph, or the less frequently seen white morph, while the Japanese Paradise-flycatcher only has one plumage morph. The identification of rufous-morphed male Blyth’s and Amur Paradise-flycatcher is quite straightforward. The male Amur Paradise-flycatcher has a glossy black hood contrasting sharply to the paler grey breast, whereas in Blyth’s Paradise-flycatcher, the face, throat and breast are uniform grey. The upperparts and tail of the male Amur Paradise-flycatcher are also more deeply chestnut with a slight purplish tinge. However, the identification of the white-morphed male is very little understood.
I had the opportunity to observe 2 white-morphed male paradise-flycatchers together at Thung Yao Community Forest (Nam Cham Forest) in Lamphun during late April 2020, when the birds were migrating through this small patch of forest. The number of both Amur and Blyth’s Paradise-flycatcher at the site seemed rather equal, but it was interesting to see that there were much fewer male Blyth’s Paradise-flycatchers than the female, whereas in Amur Paradise-flycatcher, the number between male and female was not significantly different.
The first thing that I noticed when looking at these white paradise-flycatchers that I’ve photographed was the thickness of dark shaft-streaks on the upperparts. I suspect that in Amur Paradise-flycatcher, the shaft-streaks are thinner than in Blyth’s Paradise-flycatcher, making it appear cleaner and more glistening white when seen in the field. The dark shaft-streaks seem to be slightly bolder in Blyth’s Paradise-flycatcher, as well as the dark edges to the tertials and tail feathers.
Going through photos of both species on eBird, I can also see the consistency of this feature across their distributions. This breeding Amur Paradise-flycatcher from Guangdong shows a very clean white plumage with extremely fine dark shaft-streaks (here is the female which confirms that it’s an Amur Paradise-flycatcher). On the other hand, this breeding male Blyth’s Paradise-flycatcher from Guangxi shows very bold and dense dark shaft-streaks (and here is the female).
Another feature which I noticed while observing these paradise-flycatchers in Lamphun was the different colour inside the bill. Because of hot weather, most of the birds were opening their mouths to reduce the heat showing the bright yellowish colour which is normally hidden. I noticed that in Amur Paradise-flycatcher, based on the rufous morphed birds, the colour inside the bill was more lime-yellow, while in Blyth’s Paradise-flycatcher, the colour appeared more ochre-yellow. What’s interesting was the 2 white-morphed males at Lamphun also showed different internal colour of the bill. The one that I suspect to be Amur Paradise-flycatcher showed a more lime-yellowish colour, while the other bird showed a strong ochre-yellow colour consistent to what I observed in the rufous-morphed birds.
The shaft-streaks and internal bill colour are probably the keys to the identification of white-morphed male paradise-flycatchers, but I think more studies and observations are needed to confirm this. Nevertheless, I think it’s a good start for birders to look more closely at these beautiful birds which we apparently know so little about them.