NEW ZEALAND WRENS: Acanthisittidae

PHYSICAL CHARACTERISTICS

New Zealand wrens are very small, compact birds. They have straight or slightly upturned, slender, and pointed bills, which are about the same length as the head. Their wings are short and rounded. These birds have large, stout legs with strong, gripping feet and long, slender toes. The third and fourth toes are joined at their base. These birds have almost no tail. Their soft plumage, feathers, consists of greens, browns, and white. Adults are 3 to 4 inches (8 to 10 centimeters) long, with females substantially larger than males, although males are more brightly colored than females.

GEOGRAPHIC RANGE

New Zealand wrens are found on the North and South Islands, and some of the other surrounding islands of New Zealand.

HABITAT

New Zealand wrens are found in forests, beech forests, scrublands, and alpine, high mountain, areas, especially when large amounts of insects are available. They are usually found from sea level to 1,150 feet (350 meters) in elevation.

DIET

The diet of New Zealand wrens consists mostly of insects. They forage, search for food, alone, as a bonded male and female couple, or as a family group. They forage by crawling along the bark of trees and among the leafy parts of trees in search of insects and small arthropods, invertebrate animals (animals without backbones) with jointed limbs. They sometimes forage on the ground.

BEHAVIOR AND REPRODUCTION

New Zealand wrens are weak fliers, with soft songs and calls. When landing on a perch from a short flight they often bob their body up and down. Their breeding season is from August to March. They are monogamous (muh-NAH-guh-mus), having only one mate, birds that form long-lasting pair bonds. The mating pair builds a complex nest in tree and rock crevices, narrow cracks or openings, in tree hollows or behind loose bark, in holes within tree trunks, earthen banks, walls within human-made structures, and fence posts, and sometimes on the ground in protected places. The nest consists of loosely woven materials such as moss, roots, leaves, ferns, and plant debris. There is a side entrance into the nest, which is often lined with feathers. Females usually lay two to five white eggs. Males feed nesting females and both parents feed their young. After the young leave the nest, they remain with the parents for several weeks.

NEW ZEALAND WRENS AND PEOPLE

With very few predators, animals that hunt them for food, in their customary habitats, most New Zealand wrens are not able to cope with new predators, such as those introduced by humans. It is also difficult for most of them to adapt to modifications within their environments.

MALE HELPERS FIND FUTURE MATES

Researchers have found that most rifleman adult helpers were unpaired males that later in the breeding season became paired with female offspring from a nest they had earlier helped to feed and protect. Although studies have not proven this, many experts believe that finding a female mate is easier when unmated males help out with taking care of young birds. Riflemen are a species of New Zealand wren.

CONSERVATION STATUS

Two species of New Zealand wrens are listed as Extinct, no longer existing. The two remaining species are fairly common and protected by laws.

RIFLEMAN (Acanthisitta chloris): SPECIES ACCOUNT

Physical characteristics: Riflemen are the smallest living bird species in New Zealand. They have greenish upperparts and whitish undersides with yellow wash on the sides. Females are generally duller than males and are brown striped. Males have a bright yellow-green back while females have a back that is striped with darker and lighter browns and flecked with red-brown spots. Both sexes have a slightly upturned bill, with the female bill being a little more upturned. They have white bellies and white markings above the eyes. Their wings have a yellow bar with a white spot at the end of the bar and yellowish rumps and flanks. Males are generally smaller than females, with adults about 3 inches (8 centimeters) in length and weighing between 0.2 and 0.3 ounces (6.3 and 9.0 grams).

Geographic range: Riflemen are found on both main islands (North Island and South Island) of New Zealand, except for the northern portion of the North Island. They are also found on Stewart Island, just off the southeastern coast of South Island, and the Great Barrier and Little Barrier Islands.

Habitat: Riflemen are located in various habitats including forests, scrublands, farmlands, and disturbed and regenerating habitats. They adapt easily to new environments composed of plant species not native to their normal habitats.

Diet: Their diet consists of insects, spiders, and other small invertebrates, animals without backbones. Males take prey from tree leaves while females find food within tree bark. The female's slightly more upcurved bill helps the female pry and loosen bark away from trees. They often work their way up and around tree trunks in a spiral route that takes them from the base of a tree up to 20 to 30 feet (6 to 9 meters) off the ground.

Behavior and reproduction: Riflemen are lively, diurnal, active during the day, birds. Their call is a sharp, high-pitched, cricket-like "zipt" or "zsit" that is sounded either singly or in a rapid series of separate notes. Most of their activity consists of foraging in trees, going from one tree to another, usually in an established route. Riflemen are not very strong fliers, so, they limit their flights to short ones from tree to tree, and rarely go out of their small familiar territory. They rarely go to the ground. Sometimes when perching on a branch, riflemen will quickly flick their wings.

Riflemen are monogamous birds, forming long-lasting pair bonds. Their breeding season is from August to January. Males do most of the construction of the nest. The typical nest is a rather complex structure in a tree crevice, sometimes with a dome-like roof and inside lined with spider webs and mosses. Females lay two to four white eggs. About ten days before and during the egg laying process, males will bring food to females up to nine times an hour. Both parents usually raise two broods, young birds that are born and raised together, each year. The incubation period, time that it takes to sit on eggs before they hatch, is nineteen to twenty-one days. The nestling period, time necessary to take care of young birds unable to leave nest, is twenty-three to twenty-five days, but can last up to sixty days. Eggs weigh about 20 percent of the female's weight, and are laid every other day. Males incubate during the day and females incubate at night. Hatchlings are born in an undeveloped condition, so they take longer than most birds to develop into a stage where they can fly away.

Parents often use one to three adult or juvenile helpers to help feed nestlings and fledged offspring, those able to fly. For a first clutch, group of eggs hatched together, helpers are not usually related to the parents. They help to feed and defend the chicks, and to clean the nest. Some helpers only help with one nest, but others divide their time between several nests. With helpers, parents often have less work to do. Fledged young birds from the first brood often help to feed the chicks of the second brood. The nest for the second brood is often started before the first brood has left the first nest. This nest is smaller, loosely built, and unlined. Males do not bring food to females before and during the second egg-laying period. The second clutch of eggs is usually one egg less than the first clutch.

Riflemen and people: There is no known significance between riflemen and people.

Conservation status: Riflemen are fairly common and protected by New Zealand laws and a strong conservation program. They are the most successful species of the New Zealand wrens. ∎

FOR MORE INFORMATION

Books:

del Hoyo, Josep, Andrew Elliott, Jordi Sargatal, Jose Cabot, et al., eds. Handbook of the Birds of the World. Barcelona: Lynx Edicions, 1992.

Dickinson, Edward C., ed. The Howard and Moore Complete Checklist of the Birds of the World, 3rd ed. Princeton, NJ and Oxford, U.K.: Princeton University Press, 2003.

Forshaw, Joseph, ed. Encyclopedia of Birds, 2nd ed. San Diego, CA: Academic Press, 1998.

Harrison, Colin James Oliver. Birds of the World. London and New York: Dorling Kindersley, 1993.

Perrins, Christopher M., and Alex L. A. Middleton, eds. The Encyclopedia of Birds. New York: Facts on File, 1985.