BOWERBIRDS: Ptilonorhynchidae

PHYSICAL CHARACTERISTICS

Bowerbirds are small- to medium-sized, stocky birds that are related to birds of paradise. They are known for the bower-building activities of males within some species. The bower is a shady, leafy, elaborate shelter that the male builds for courtship to females. Bowerbirds show a range of colors in their plumage (feathers) including bold patterns of yellow, orange, green, and lavender with gray or black in many species; plain brown or gray in other species; and a few species that are spotted. In the brightly colored species, males are brighter than females; while in the duller colored species, males and females look alike. There are about fifty to sixty plumage variations within bowerbirds. Some species have only one primary color that blends into their environment, while others have two primary colors, with adult males showing colorful plumages and females being drab. Nestlings (young birds unable to leave the nest) have pinkish, orange-pink, or pale flesh-colored skin. Plumages of juveniles and immature males are similar to those of adult females. Males take five to seven years to fully acquire adult plumage.

Bowerbirds have a stout, powerful bill, except for the thinner, longer bill of regent bowerbirds and the falcon-like mandibles (upper and lower parts of bill) of tooth-billed bowerbirds. The bill is dark brown to black but can be pale; slightly hooked at tip in all species; and can be slightly downcurved, straight, thin and weak, or heavy. Bowerbirds have a black, pale yellow, or orange-yellow mouth; strong legs and feet that are usually dark brown, olive-brown, olive, blue-gray, or black; and toes with hard scales.

Some species have a crest (growth on top of head) of elongated feathers, often brilliantly colored. In other species, the crest forms a complicated mane that hangs over the upper back. Adults are 8.7 to 14.6 inches (22 to 37 centimeters) long and weigh between 0.18 and 0.64 pounds (80 and 290 grams).

GEOGRAPHIC RANGE

Bowerbirds are found primarily on the mainland of New Guinea, but also in Australia and the offshore islands of both countries.

HABITAT

They inhabit rainforests, rainforest edges, moss forests, woodlands, open riverine (located near river) forests, borders between forests and grasslands, open woodlands, savannas (flat grasslands), and semi-deserts.

DIET

Their diet consists of fruits from trees and bushes along with arthropods (invertebrate animals with jointed limbs) and other animals such as insects, spiders, small snakes, worms, frogs, birds, and skinks (small insect-eating lizards). They also eat flowers, leaves, seeds, and sap.

BEHAVIOR AND REPRODUCTION

Depending on species, bowerbirds can be monogamous (muh-NAH-guh-mus; having one mate) or polygynous (puh-LIJ-uh-nus). Monogamous pairs defend a territory, while males do not help with nest building, incubation (process of sitting on eggs), or the raising of young, though they do help with feeding. Males of polygynous species defend only the nearby area of their bowers. They court and mate with many females, being able to supply many females and their young with large amounts of food in territories with plenty of fruits. Unlike any other bird families, a polygynous male clears a courting area where he builds a bower, a complex symmetrical structure of sticks, grasses, and other vegetation, and decorates it with various colorful objects.

The three types of nesting structures made by bowerbirds are: courts (cleared and decorated with leaves); maypole bowers (constructed of branches, sticks, saplings, and orchid stems along with an elaborate and decorated mat underneath it); and avenue bowers (made of two parallel, vertical walls of sticks or grass stems placed onto a foundation that is set on a ground court that may extend past one or both ends of the bower, making a platform). Courts and bowers are decorated with flowers, leaves, lichens (LYE-kenz), fruits, beetle wing cases, insect skeletons, snail shells, tree resin, bones, river-worn pebbles and stones, and tail feathers of parrots and plumes of adult males of certain birds of paradise. The incubation period (time to sit on eggs before hatching) is twenty-one to twenty-seven days. The nestling period (time necessary to take care of young unable to leave nest) lasts seventeen to thirty days. They live longer than most birds, many twenty to thirty years.

BOWERBIRDS AND PEOPLE

A few groups of native New Guinean and Australian aborigines have used the crests of some male species as clothing decorations, while some natives believe that male bowerbirds use the same techniques as male humans to find a mate; still other natives believe that some species steal human bones for their own ceremonial purposes. Eight species have been bred in aviaries (large enclosures or cages for birds).

CONSERVATION STATUS

One species of bowerbird is considered Vulnerable, facing a high risk of extinction, and one species is listed as Near Threatened, close to becoming threatened with extinction.

SATIN BOWERBIRD (Ptilonorhynchus violaceus): SPECIES ACCOUNTS

Physical characteristics: Male satin bowerbirds have iridescent (lustrous appearance) black plumage, bright lavender eyes, pale yellow bill, and light legs. Females are slightly smaller than males, with green, gray-green, brown, and buff colorings that help to camouflage them (blend into the environment). Adults are about 13 inches (33 centimeters) long, with females weighing between 0.38 and 0.57 pounds (170 and 258 grams) and males weighing between 0.38 and 0.64 pounds (173 and 290 grams).

Geographic range: They are found in eastern and southeastern Australia.

Habitat: Satin bowerbirds inhabit rainforests and eucalypt forests, clearly preferring forest edges and nearby woodlands with dense sapling understories. During winter months, they like more open habitats such as pastures and urban and suburban areas.

Diet: Their diet consists mostly of fruits but also some insects. They also eat flowers, leaves, herbs, nectar, seeds, and animals including cicadas, beetles, and other arthropods. Satin bowerbirds forage from the forest canopy during summer, but eat from the ground in winter.

Behavior and reproduction: Males clear off a circular area on the rainforest floor and build avenue bowers to attract females. They are usually built about 990 feet (300 meters) apart when along rainforest edges, but are spaced further apart in rainforest patches and woodlands. Decorative bluish and greenish yellow objects such as flowers, fruits, parrot feathers, snakeskins, snail shells, and human-made objects (such as pen caps) are often used. Bowers are used from late August/September through December (peaking in October). Adult males make their presence known with a clearly-whistled "quoo-eeew," various harsh and scratchy hisses (called "skraa" calls), and vocal mimicry, often sung within the understory above his bower.

Satin bowerbirds are polygynous. Breeding begins in August/September and continues through February (peaking in November/December). Nests are usually open cup-shaped structures built in trees or bushes, but sometimes in vines and mistletoe, normally at 7 to 130 feet (2 to 40 meters) off the ground. Nests are made with sticks and twigs and lined with green and dry leaves. Females lay one to three colored and blotched eggs. The incubation period is twenty-one to twenty-two days. The nestling period is seventeen to twenty-one days.

Satin bowerbirds and people: Male satin bowerbirds often remove people's jewelry, keys, and other items in order to decorate bowers.

Conservation status: Satin bowerbirds are not threatened. They are commonly to reasonably abundant birds in their current habitats, but have lost much territory to human land use. ∎

SPOTTED BOWERBIRD (Chlamydera maculata): SPECIES ACCOUNTS

Physical characteristics: Spotted bowerbirds look similar to song thrushes, being relatively plain in appearance. They are mottled brown with a lilac to pink bar across the back of the neck. This vivid bar, which easily recognizes them, is erected into a crest-like peak during times of anxiety or excitement. Adults are 10.6 to 12.2 inches (27 to 31 centimeters) long, with females weighing between 0.27 and 0.36 pounds (124 and 162 grams) and males weighing between 0.28 and 0.33 pounds (125 and 150 grams).

Geographic range: Spotted bowerbirds are found in the interior of Queensland south of 20 degrees south latitude, except the far west and southwest; interior of west and central New South Wales, except the far western border country; and extends a short way into the northwest corner of Victoria and just into South Australia along the Murray River system. They are found from sea level to about 1,640 feet (500 meters).

Habitat: Spotted bowerbirds are found among brigalow (Australian acacia tree that grows in semiarid regions) and open eucalyptus woodlands, with a preference for riverine woodlands.

Diet: They eat fruits, flowers, leaves, seeds, and arthropods. Nestlings are fed mostly grasshoppers.

Behavior and reproduction: Spotted bowerbirds build avenue bowers beneath low bushes or shrubs. The nests are made from grasses and are often 3,300 to 6,600 feet (1,000 to 2,000 meters) apart from each other. The walls are about 7.8 to 19.7 inches (20 to 50 centimeters) high. Up to 1,000 or more decorations such as berries, seedpods, pebbles and stones, bones, snail shells, and glass are attached to the bowers. Adult males occasionally make loud, harsh churrings and other notes (including vocal mimicry) in order to make themselves known.

Spotted bowerbirds are polygynous. Breeding occurs during July through March (peaking from September to February). Males make a sparse open cup-like nest in trees and bushes, often 10 to 40 feet (3 to 12 meters) off the ground. The loose bulky foundation for nests are made of dead twigs and sticks, with fine twiglets and (sometimes) dried grass stalks used for the nest. Males spend much time watching and tending to their bowers. Two to three eggs are laid. The incubation and nestling periods are unknown.

Spotted bowerbirds and people: People often cage spotted bowerbirds within avaries. The birds frequently steal items from homes, camps, and vehicles for decorating their bowers. People often kill them when they become pests within gardens and orchards.

Conservation status: Spotted bowerbirds are not considered to be threatened. They have declined in some areas because of illegal hunting and killing of the birds by humans, domesticated and feral cats, and foxes, and the widespread clearing and/or modification of habitat. Populations are listed as endangered, however, within the state of Victoria. ∎

FOR MORE INFORMATION

Books:

del Hoyo, Josep, A. Elliott, J. Sargatal, J. 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.