Black Robin

Black Robin or Chatham Island Black Robin, entirely sooty-black, robin-like bird found only in the Chatham Islands about 800 km (500 mi) east of New Zealand. The black robin is a protected, threatened, and endemic species.

At approximately 15 cm (6 in) in length and weighing from 22 g (females) to 25 g (males) (or about • oz) it is smaller than the robins of mainland New Zealand. The black robin is not closely related to European, American, or Asian robins, but superficially resembles these since it has an upright posture, large, rounded head, large eyes, rectal bristles at the base of the bill, and an unusually trusting disposition.

The black robin prefers low forest or scrubland with a closed canopy, open understorey, and abundant margins. In taller, more mature forests, population densities tend to be lower.

Food comprises live invertebrates: small cockroaches, spiders, moths, caterpillars, aphids, and the endemic cricket-like weta are favoured food items. Most foraging takes place on or near the forest floor. Black robins hop as opposed to walk, and rarely hawk for insects.

Black robins are territorial all year, but especially so in the breeding season when the male patrols his territory and sings from prominent perches by day and for much of the night. The song of the male is a simple, melodious, and sustained phrase of five to seven notes. Females sometimes sing brief phrases but never the full song. Black robins also have a high-pitched single note contact call. Territories range from approximately 0.5 hectares (5 sq km or about 2 sq mi) to many hectares in area, depending on habitat quality and social pressures within the population. Robins usually keep the same partner year after year. From June onwards, winter in the Southern hemisphere, males sing their territorial song, and from September (springtime) they start courtship feeding.

The female generally builds two or three nests but only one is completed. It is a neat, open cup of twigs, bark, leaves, and moss held together with spider webs, and densely lined with moss and feathers. It is usually built in a shallow cavity, a hollow branch or rotten stump, or occasionally in an old blackbird nest in a tangle of vines. Black robins readily use nest boxes. They lay one to three cream-coloured eggs with purplish-brown blotches and spots. Most eggs are laid between October and November, and each pair usually raises only one brood per year. However, they lay more eggs if they lose a clutch, and this behaviour was exploited to induce black robins to lay up to three clutches in a season during the species’ dramatic rescue from near-extinction—only five birds remained including just one reproductive female nicknamed “Old Blue”—in the 1980s. The female alone incubates the eggs for about 18 days and broods the nestlings. Both parents feed the chicks during their nestling period of approximately 23 days and fledging period of about six weeks. Young birds are capable of breeding at one year, but most do not until two years of age.

The mean life expectancy of black robin is approximately four years. However, “Old Blue”, the matriarch of the restored species, lived for about 13 years.

Scientific classification: The black robin belongs to the Australasian robin family, Petroicidae, of which there are roughly 40 species in about 14 genera, found in Australia, New Guinea and the south-west Pacific. Ten of these, including the three species endemic to New Zealand, are in the genus Petroica. The black robin is classified as Petroica traversi.