Horsfield's Frogmouth (Batrachostomus javensis) - HBW 5, p. 287

Taxonomy: Podargus Javensis Horsfield, 1821, Java.
Much confusion over species-limits with regard to this and its close allies. Formerly considered conspecific with B. cornutus by some, but a combined study of vocalizations and museum specimens in 1978 confirmed earlier suggestions that it should be regarded as a distinct species. Race affinis sometimes considered a distinct species. Sometimes treated as conspecific with B. hodgsoni, but differences in bill size and structure, development of facial bristles, relative tail length and vocalizations, and also perhaps in bare-part colours (bill said to be often more straw-coloured), too great for them to be considered even as forming a superspecies. Race continentalis is apparently connected to affinis by an intermediate population around Khao I Phrom in C peninsular Thailand. Birds from Palawan, Culion I and Banggi I often separated as race chaseni, but appear inseparable from affinis; recent claim of a new species (B. pygmaeus) from Palawan (Basuanga I) seems unconvincing, the single specimen on which description is based being little different from local “chaseni” (= affinis). Three subspecies recognized.