Habitat
Secondary lowland dipterocarp, peatswamp and kerangas forest to lower montane forest. Less commonly in primary forest, mangroves, plantations. From sea-level - 1,200 m.
Voice
A repeated, cheerry, upwardly inflected series of breathless whistles 'whit-whit-whit-whit-wit-wit', the last two notes sharply louder and higher.
Asian Red-eyed Bulbul (Pycnonotus brunneus) [XC838637]
by id from South Siantan, Kepulauan Anambas Regency, Riau Islands, Indonesia (song)
Asian Red-eyed Bulbul (Pycnonotus brunneus) [XC244184]
by Marc Anderson from Rainforest Discovery Center, Forest Trail, Sepilok, Sandakan, Sabah, Malaysia (song)
Subspecies
Probably warrants placement with Spectacled Bulbul (Pycnonotus erythropthalmos) in a separate genus; both appear rather distantly related to the "Pycnonotus capensis complex" and "Pycnonotus cafer complex". Subspecies zapolius hardly distinguishable, and perhaps unworthy of taxonomic recognition. The form on Tioman I (off eastern Peninsular Malaysia) previously misidentified as belonging to this subspecies. Described subspecies zaphaeus (from Pulau Matasiri, off south-eastern Borneo) indistinguishable from nominate.
The following 2 subspecies are recognised:
brunneus Blyth, 1845 - Southern Myanmar (Tenasserim south of c. 12·5° north), extreme southern Thailand, Peninsular Malaysia (including Tioman I), Sumatra (including Banyak, Nias, Batu, probably also Bangka I) and Borneo (including Banggi, Karimata and Larot).
zapolius Oberholser, 1917 - Anamba Is.
Similar Species
Cream-vented Bulbul (Pycnonotus simplex) which is slightly smaller, iris is red not orange, and underparts are paler.
References
See References.