Species: Brachydiplax sobrina
Common name(s): Little Blue Marsh Hawk
Synonyms: Brachydiplax gestroi (Selys, 1891); Brachydiplax indica (Kirby, 1889) *
Habitat: Large, exposed rivers, small lowland forested ponds
Province(s) sighted: Large river, Lomsak environs (Lomsak); River Chi, Khon Kaen environs; small lowland forested ponds (Udon Thani province)
Sightings (by me): Rare (though common in one area of Udon Thani province)
A really difficult genus to ID is Brachydiplax. However, with the help of Noppadon Makbun and Oleg Kosterin, I am now able to ID species in the field (hopefully). With Brachydiplax sobrina I am leaning towards their preferred habitat being large exposed rivers, as opposed to marshy/weedy ponds preferred by other species in the genus - though I could be completely wrong, especially as its common name is Little Blue Marsh Hawk.
(Yes, I am wrong ... I have seen this species thriving at small farmer's ponds.)
The male is almost identical to other species in the genus. However, it can be identified by its antenodal crossveins. This species has 7 as opposed to 8-9 of B. farinosa. I first saw this species back in 2008, I saw it again briefly in 2011 and then recently in Udon Thani province where it seemed fairly abundant, though mature males were hard to approach.
An unfortunate ending ...
The young male
Similar to the older male, but the thoracic markings are still visible.
The best way to separate this species ...
I haven't managed to spot the female, though it was photographed recently at the same place in Udon Thani, by my fellow Issarn dragon hunter, Joe Hartman. I will return to find her one day soon.
* [source: http://www.iucnredlist.org]