Key to Subspecies.
A. Whole abdomen, posterior flanks, vent and under tail-coverts white; larger,
wing average about 130 mm D. c. caerulescens, p. 365.
B. Abdomen nearly always dark, only vent . and under tail-coverts white; smaller,
wing average about 112 mm D. c. leucopygialis, p. 366.
Those two races merge into one another in a remarkable manner and iv would almost seem as if there were two species—one, caerulescens, a white-bellied Indian bird with a small race inhabiting North-West Ceylon, and a second species, leucopygialis, with a dark belly, inhabiting Ceylon only.
The Indian bird throughout its area has a white abdomen, though this varies considerably in extent individually and somewhat decreases as one works farther South. Specimens exactly similar to Southern Indian birds in coloration are found over a great part of Ceylon but in size all these agree with the smallest Ceylon birds measuring in the wing only 104 to 111mm. The majority also have the browner breast of the Ceylon birds, though this brown or grey tint varies somewhat throughout the whole area of this species.
For the present I retain the whole of the Ceylon birds under the name of D. c. leucopygialis.