On the weekend of 7-8 February, I joined the annual Doi Inthanon Bird Census held by Lanna Bird and Nature Conservation Club. The place is particularly good for leaf warbler lovers like me since 3 species (as far as we know) can be seen here easily. These include the range-restricted resident Blyth’s Leaf Warbler (Phylloscopus reguloides), the more widespread resident Davison’s Leaf Warbler (P. davisoni) and the widespread winter migrant Claudia’s Leaf Warbler (P. claudiae). During this recent trip, I observed all 3 species at different altitude of Doi Inthanon and could particularly get good images of the Blyth’s Leaf Warbler.
I’ve written a series of how to identify this Blyth’s/White-tailed Leaf Warbler complex which can be access here. In general, Davison’s has more yellow hue to its plumage than Blyth’s and Claudia’s, particularly on supercilium, face and median crown stripe. However, this can be very variable. The best way is to check for the undertail pattern, of which Davison’s shows completely white inner web to the outermost pair of tail feathers. Blyth’s and Claudia’s are almost identical plumage-wise. Unlike Davison’s, both species show grey undertail with thin white edge to the inner web of outer tail feathers with Blyth’s having more white than Claudia’s.
At Doi Inthanon, Davison’s Leaf Warbler can be found throughout a wide range of altitude from ca. 1,000 m to the highest summit (2,565 m above sea level). Claudia’s Leaf Warbler can also be found through a wide range of altitude from lower foothills to at least about 1,500 m above sea level. So far, I still haven’t seen this species around the summit. On the other hand, Blyth’s Leaf Warbler is almost exclusively found above 2,000 m above sea level, but might move down to lower altitude (ca. 1,500 m) in winter (see this post).
On the morning of Feb 7th, I visited Doi Pha Tang area (ca. 1,300 m above sea level) and found a nesting pair of Davison’s Leaf Warblers. They were busy building a nest located on a slope right on the roadside. The nest was only about 1 ft. above the ground but was well concealed by grass and fallen leaves. This is probably the earliest nesting record of this species for me. Compare to this nest I found at Doi Lang in March.
At the summit, there seemed to be more Blyth’s Leaf Warblers than Davison’s, which made me feel strange because I remember visiting in rainy season and couldn’t locate any Blyth’s Leaf Warbler. I also started to be able to recognise the songs of Blyth’s and Davison’s Leaf Warbler. Throughout the morning, I heard and observed many Blyth’s Leaf Warblers singing in the summit trail. The song of Blyth’s seems to have clearer notes and less slurred than Davison’s.
There’s a particularly tame pair of Blyth’s Leaf Warblers around the entrance of the summit trail boardwalk. They might be looking for a nesting site since they were staying very close to the ground unlike most foraging Blyth’s Leaf Warblers that I’ve seen. Despite the very dim light inside the trail, I managed to get many close up shots of the birds.