Yellowhead Mohoua ochrocephala Scientific name definitions

14–15 cm; 28–32 g. Has head and neck bright yellow , crown and hindneck with varying amounts of olive mottling; upperparts olive-brown, grading to olive on uppertail-coverts; remiges dark brown, edged olive on outer webs, wing-coverts yellowish-brown; tail dark yellow-olive; chin, throat and breast bright yellow , lower belly pale greyish-white, breast side, flanks and thighs often washed pale brown, undertail-coverts off-white, tinged yellow; iris very dark brown; bill and legs black. Some females have greater amount of mottling on head, but sex of many individuals indeterminable. Juvenile has upperparts more olive than adult’s, underparts paler.

Native southern beech (Nothofagus) forest , preferably large tracts with open understorey; in mountain valleys up slopes, to c. 900 m. Historically occupied podocarp-hardwood forest, but gone from most by early 1900s.

Local seasonal movements, usually in winter flocks; moves along same elevation, also descends from montane valleys.

Invertebrates, mainly insects; also small fruits and nectar. Feeds mainly in middle to upper layers , in subcanopy and canopy: less than 4% of foraging on ground, 10–14% in lower understorey, 18–34% in upper understorey, 34–41% within canopy, 14–30% in top of canopy. Most foraging takes place in foliage (c. 46%), less on trunks (c. 17%), dead wood (c. 14%) and branches (c. 21%). About a quarter of foraging time used in scanning for prey. Gleaning comprises c. 90% of foraging attacks. Food items held in foot and raised to bill or repositioned in bill. Forms foraging flocks of 3–40 individuals; also frequently joins mixed-species flocks.

Song 6–8 musical, rapidly repeated, frequently varied, trilled notes ; rattle of rapid staccato notes often added to end of song. Alarm a harsh scolding note; also “lukaart, lukaart” call by female a few days before and after eggs hatch.

Season Oct–Feb, most eggs Nov–Dec; double-brooded. Breed as monogamous pair, usually with one helper. Territorial while breeding. Nest built by female, a cup-shaped structure of rootlets, twigs, grass and other plant material, lined with finer vegetation and feathers, placed 1·7–31 m (usually c. 14–15 m) from ground in cavity in dead or live tree trunk or stump, usually with top rim more or less level with bottom edge of entrance; mean diameter of entrance hole 7·7 cm, opening 0–31 cm (mean 13 cm) from bottom of hollow. Clutch 2–4 eggs, pinkish-white to reddish-cream, spotted and blotched pale and dark reddish-brown, occasionally grey with pale brown markings, 23–24 × 17·5–19 mm; incubation by female (in some instances two females share role), fed by male, period c. 21 days; chicks fed by both parents and any helper present, nestling period c. 22 days; all also feed fledglings, which dependent for several days and stay in small family group for some time; female sometimes builds new nest and lays eggs before first brood has fledged. Nests parasitized by Long-tailed Koel (Urodynamis taitensis). Hatching success 28·6–69·2%, 38·1–80% of nestlings fledge; extensive predation on nests, chicks and sitting females by introduced stoats (Mustela erminea) and black rats (Rattus rattus). Maximum recorded longevity at least 16 years.

ENDANGERED. Restrictedrange species: present in South Island of New Zealand EBA. Uncommon and very patchily distributed; restricted to large tracts of native forest, mainly in Fiordland and Arthur’s Pass. Current population fewer than 3000 individuals. Formerly abundant, but suffered dramatic decline from 1880s and during 20th century, much of this since 1960s; now absent from c. 75% of former range. Major threats are clearing and modification of habitat, resulting in loss of suitable nesting and feeding trees. In addition, predation by stoats and black rats a significant threat, periodic population explosions of these mammals causing marked periodic local losses of birds; present species appears to be particularly susceptible to small predatory mammals due to its hole-nesting and hole-roosting habits (1 Lawrence, B.L. and Low, M. (2012). Does hole-roosting behaviour of mohua (Mohoua ochrocephala) increase the risk of predation by introduced mammals? Notornis. 59(1-2): 85–87. Close ); population levels found to rise in places where stoat-control programmes undertaken.