Chatham Robin Petroica traversi Scientific name definitions

15 cm; 20–25·5 g. Plumage is completely dull black; iris  dark brown; bill  and legs black. Sexes alike. Juvenile  is like adult, but with fine faint shaft streaks on head and underparts.

Chatham Is: Mangere I; introduced on Rangatira I.

Forest and scrub, usually with closed canopy.

Sedentary.

Invertebrates, mainly insects. Most prey obtained on ground, either by pouncing from low elevated perch or by gleaning from leaf litter. In short study, individuals did 80% of feeding on ground, 5% at 0·1–10 m, 9% at 10–20 m, 6% above 20 m; fed from leaf litter (77%), bare ground (3%), branches and trunks (12%), foliage (5%), in air (3%); prey captured by being pounced on (57% of captures), gleaned (35%, including from leaf litter), in sally-strike (3%) and in flutter-chase (5%). Frequently moved between perches, 2–9 times per minute. In one set of observations, c. 85% of waking time spent in foraging.

Song a simple series of pure notes, individual repertoire 5–13 notes; total number of notes on Little Mangere I (1973/74) 48 notes. Contact call a single high-pitched note; also, aggressive “chuck” and descending series of notes.

Season short, eggs Oct–Nov; usually one brood, but experienced pairs sometimes produce more. Territorial throughout year. In courtship, male chases female through trees; male feeds her during courtship and through incubation. Nest built by female, a cup constructed of twigs, bark and dry leaves, bound externally with spider web, lined with moss and feathers, placed usually below 10 m in cavity in hollow tree or in low stump buried in vine tangle, or, where these not available, in range of other situations, including on ground; territory size c. 0·7–2 ha. Clutch 1–3 eggs  , usually 2  , creamy white with purplish-brown spots and blotches, 22 × 17 mm; usually laid 8–12 days (but up to 1 month if weather inclement) after completion of nest; incubation by female, period 17–19 days; chicks  brooded by female, fed  by both parents, leave nest at 20–23 days; young fed by both adults for 3–6 weeks after fledging. Success good: can fledge  three young, usually one or two; under active manipulation, female can produce four clutches in season (extending laying period to Jan), will readily accept replacement of eggs with nestlings. First breeding usually at 2 years, sometimes at 1 year. Longevity 10–12 years.

ENDANGERED. Restricted-range species: present in Chatham Islands EBA. Global population in 2000 was c. 250 individuals. Before arrival of Europeans probably lived throughout Chatham Is, but human-related activities caused its extirpation on most islands. Known to have been present on Mangere I and Little Mangere I when first discovered, and possibly also on Chatham I and Pitt I before this, but no records. Around 1900, when cats had eliminated Mangere I population, only c. 25 pairs remained on Little Mangere I; here they were safe from predators, but extensive wind damage caused erosion, with loss of food and habitat, and by 1972 only 18 individuals left. By 1976 as few as seven remained; these were captured and moved to Mangere I, where, despite breeding attempts, no success. Numbers then dropped to five individuals, consisting of three males and two females; only one of the females bred, eventually producing eleven chicks in 4 years. In 1980/81 breeding season, eggs removed and cross-fostered in nests of Chatham Gerygone (Gerygone albofrontata), the parent robins quickly re-laying; the gerygones, however, proved unsuitable foster-parents because of their slow feeding rate. In following season, P. macrocephala on Rangatira I employed as fosterers, with high success; in order to avoid imprinting, young were returned to natural parents before fledging. In 1983, a new population of present species was established on Rangatira, to which two pairs of adults were translocated. Potential for genetic problems is being monitored; a genetic assessment in 2015 showed lack of evidence of any danger of population decline or extinction through hybridization with P. macrocephala (1 Cubrinovska, I., M. Massaro, and M. L. Hale (2016). Assessment of hybridisation between the endangered Chatham Island black robin (Petroica traversi) and the Chatham Island tomtit (Petroica macrocephala chathamensis). Conservation Genetics 17(2):259–265. Close ). Introduced Common Starlings (Sturnus vulgaris) kill nesting birds and destroy eggs and chicks.