Habitat
Primary and secondary lowland dipterocarp forest usually near moving water in riverine and peatswamp forest, mangroves, plantations. From sea-level - 750 m.
Subspecies
Considerable individual variation throughout most of range renders defining of geographical subspecies difficult; apparent general clinal trend in certain characters, such as increase in size and decrease in amount of white in tail from north to south, but no constant differences between populations. Variation in characters used to define subspecies requires further study. Described subspecies lemniscatus (Sumatra, Bangka I and Belitung I) and tenebrosus (south-eastern Sumatra) considered synonymous with nominate; siamensis possibly inseparable from malaccensis.
The following 4 subspecies are recognised:
affinis Blyth, 1846 - South-western Myanmar. Considered by some authors to be a distinct species, Irrawaddy Broadbill (Cymbirhynchus affinis).
siamensis Meyer de Schauensee & Ripley, 1940 - Southern Myanmar (Tenasserim), south-western and southern Thailand (except extreme south), Cambodia, southern Laos and southern Vietnam.
malaccensis Salvadori, 1874 - Extreme southern Thailand and Peninsular Malaysia; formerly also Singapore.
macrorhynchos (Gmelin, 1788) - Sumatra, Bangka I, Belitung I, and Borneo (including Pulau Laut, off southern coast).