Geographical variation considerable. Most distinctive groupings of taxa are the two north-easterly forms guttaticollis and roberti, with white throats marked by dark cone-shaped flecks, and the Sundaic nominate, diluta and exsul, with black-and-white-stippled submoustachial areas, whiter throats, darker general coloration and (less obvious in exsul) bolder, clearer white streaking on brown breast and flanks; nominate and diluta also differ (recordings of exsul unavailable) in having even-pitched rather than downslurred whistles (other taxa except granti, which upslurs), supporting likely species rank for these Indonesian taxa (and posing an intriguing question about granti)#R. Race bakeri weakly differentiated from davisoni. Race laotiana often synonymized with amyae, but birds of latter race from Tonkin (N Vietnam) notably larger and longer-billed than other races; further study required. Birds from SE Laos presumed to be laotiana. Proposed race mendeni (from S Sumatra highlands) considered a synonym of diluta. Thirteen subspecies recognized.
Food and feeding
Status and conservation
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