Mar 11-12, 2017
In the middle of March (2017), I had a great opportunity to observe nest building of a pair of Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis) on Ang Ka, summit of Doi Inthanon National Park, Thailand. The nest was been building on a soil wall beside the car park area, found by Wichyanan Limparungpatthanakij, my senior experienced bird watcher. This is the first nesting record with photograph evidence of this species in Thailand.
From my observation, the nest looks like a small shallow scoop concaved into the soil wall. The entrance is quite open, but may be neglected unless thoroughly watch. One of the pair carries nesting material (Mostly bryophyte moss which is abundant on Ang Ka) to the nest, go inside, and decorate the hollow, while another one waits and watches on a small tree above the soil wall until the one comes out. Then both fly away to continue seeking for nesting material.
During one of the mate decorates the nest, another one often sings a full song and also does a Wing Flicking Behaviour.
Wing Flicking/Flapping Behaviour is diagnostic!
Blyth’s Leaf Warbler do their Wing Flicking Behaviour by flapping either of their wings up-down (just one side at the time alternatively). Whereas their couplet, Davison’s Leaf Warbler (Phylloscopus davisoni) flap their wings both sides simultaneously.
By the way, it is still a question what the actual reasons of Wing Flicking Behaviour in both species are. The initial guess could be courtship or territorial behaviour. However, many times, we observe that they also do wing flicking during their routine activity, such as foraging, outside their breeding season. That could be either territorial behaviour or usual behaviour that they normally do.
Blyth’s Leaf Warbler vs Davison’s Leaf Warbler
Confusion always occurs for the identification of these two species, since their physical appearance is almost the same except under-tail pattern.
The photo above shows the under-tail pattern of Blyth’s Leaf Warbler which are almost grey with the white edges. On the other hands, Davison’s Leaf Warbler have almost white on under-tail feathers (See photo below). Therefore the under-tail pattern is the most important mark for the identification of these two species.
Watching Phylloscopus Warblers is always fun. There are things to learn about their characteristics and behaviours. Although they are very active and naughty, I turn that to be my challenge and acquisition of knowledge, until now LBJ becomes my favourite job!