Zosterops atrifrons Wallace, 1864

Taxonomy: Zosterops atrifrons Wallace, 1864, Manado, north Sulawesi. Forms a superspecies with Z. atriceps, Z. somadikartai, Z. nehrkorni, Z. stalkeri, Z. minor, Z. meeki and Z. hypoxanthus. Was formerly sometimes treated as conspecific with all except first two of those. Is ecologically and behaviourally close to Z. anomalus, with vocal resemblance also, and has in the past been considered its sibling species in N Sulawesi. Races may constitute two separate species, nominate race and surdus representing one species and sulaensis and subatrifrons the other; latter would then include birds of this species found near L Matano (N end of SE peninsula of Sulawesi, more than 100 km from nearest known population), having relatively long tail and distinctive plumage (distinct yellow rump, golden-yellow throat, yellow undertail-coverts, white rest of underparts, legs dark grey), which presumed to represent an undescribed race. Four subspecies currently recognized. (source: Handbook of the Birds of World)