The morepork (Ninox novaeseelandiae), also called the ruru, is a small brown owl found in New Zealand, Norfolk Island and formerly Lord Howe Island. The bird has almost 20 alternative common names, including mopoke and boobook—many of these names are onomatopoeic, as they emulate the bird's distinctive two-pitched call. Three subspecies of the morepork are recognized, one of which is extinct and another that exists only as a hybrid population.
The morepork is 26 to 29 cm long, with the female slightly larger than the male. Females are slightly heavier at 170–216 g compared with the male's 140–156 g. The morepork has generally dark brown head and upperparts, with pale brown spots on head and neck and white markings on the rest of the upperparts, with a pale yellow-white supercilium (eyebrow), dark brown ear coverts, and buff cheeks. The eyes are yellow to golden-yellow. The feathers of the chin and throat are buff with dark brown shafts. The feathers of the underparts are mostly dark brown with buff and white spots and streaks, with the larger markings on the belly making it look paler overall. The upper tail is dark brown with lighter brown bars. The cere and bill is pale blue-grey with a black cutting edge. The feet are orange or yellow with blackish claws.
Young moreporks do not attain adult plumage properly until their third or fourth year. The tips of juvenile's feathers are white and fluffy, remnants of the nestlings' down. These are worn away over time, persisting longest on the head. The feathers of the head, neck, and underparts are fluffier overall. Their plumage is a darker and more greyish brown overall than that of adults.