Robin, Chatham Islands

Petroica traversi

phylum: Chordata

class: Aves

order: Passeriformes

family: Muscicapidae

status: Endangered, IUCN Endangered, ESA

range: New Zealand

Description and biology

The Chatham Islands robin (also known as the black robin) is a species of the New Zealand robin. It has coal black feathers, legs, feet, and bill. The adult robin is about 6 inches (15 centimeters) tall and weighs just under an ounce (23.4 grams). It is similar in size to a sparrow but has longer legs. Females are smaller than males. The Chatham Islands robin has dark brown eyes that provide excellent vision for hunting in the dark. It hunts for food both day and night, foraging through the litter (layers of dead leaves and twigs) on the forest floor for worms, grubs, cockroaches, and particularly for an insect related to the grasshopper called the weta. Chatham Islands robins are noted for their song, which fills the forests around them during breeding season. They fly only short distances, from branch to branch, and stay in the lower branches of the forests in order to avoid the strong winds that blow over the islands. They are territorial animals, particularly

during breeding season, and will protect their home areas from other birds of their species. They can live to be about 13 years old.

Chatham Islands robins are usually monogamous—they stay with the same breeding partner throughout their lives. When it is breeding time, the female makes a nest in a hollow tree or tree stump and usually lays two eggs at a time. She incubates the eggs (sits on them to keep them warm) and the male brings her food. The eggs hatch in about 18 days and the chicks begin to fly and leave the nest after 3 weeks. The parents continue to feed the chicks for a couple of months after they hatch, long after they leave the nest.

Habitat and current distribution

Chatham Islands robins live in the lower branches of a scrub-forest habitat. There are currently only two populations of this species, one on South East Island and the other on Mangere Island of the Chatham Island Group of New Zealand. There is a total population of about 250 birds.

History and conservation measures

The Chatham Islands robin has virtually come back from extinction and is one of the most tremendous success stories in conservation (protecting nature). However, there is much to be done before the species is out of trouble.

The range of the robin once encompassed most of the Chatham Islands. When Europeans arrived in New Zealand in the mid-nineteenth century, they began clearing the forests and destroying the habitats vital to the species. They also introduced rats and cats, predators to the robin. By 1880, the range of the Chatham Islands robin was severely reduced, and the species existed only on Little Mangere Island.

By the late 1970s, there were only seven birds left to represent the entire species. Because the habitat on Little Mangere had been badly damaged, scientists very carefully moved these last seven robins to Mangere Island. The birds were given a home in a forest that had been newly replanted, where the habitat was protected. For several years no mating took place and, by 1981, two of the seven birds had died. Only one female Chatham Islands robin remained in the world. Her name was "Old Blue" (named after the color of the band that scientists had placed on her leg in order to track her.) The future of the species seemed doomed.

Then, a group of scientists with the New Zealand Wildlife Service (now the Department of Conservation) set up a black robin recovery project on the islands. When Old Blue mated with one of the remaining males, "Old Yellow," her eggs were placed in the nests of Chatham Islands tit females, which became foster parents to the robin chicks. This project produced many new young, and soon a portion of the new Chatham Islands robin population was moved to Southeast Island. By 1999, the two locations, Mangere and Southeast Island, were home to about 259 Chatham Island robins, and plans were underway to open more critical habitat for the species. In these areas, there are no predators and the habitat is restored.

The spectacular recovery, from 5 birds to 259 birds in about 15 years, is still overshadowed by the fact that all of the new population stems from a single breeding pair, Old Blue and Old Yellow. Because of this, the gene base (the number of biological units that pass on hereditary traits) of the species is very low. So far, this has not been a problem for the new and growing populations, but because all the birds in the species will have similar weaknesses, a newly introduced predator or disease could drastically reduce the populations again.