The unique bowerbirds of Northeastern Australia

PSA Journal, July, 2004 by Graeme Guy

The bowerbirds are a monophyletic family of passerines (perching birds) consisting of eighteen species in eight genera whose distribution is limited to New Guinea and Australia. All but three species are thought to be polygynous (male breeds with several females in the same season) with males providing no parental care. These polygynous bowerbirds have historically been divided into three groups: those that build no bowers, those who construct two parallel walls of sticks (avenue builders) and those whose bower is based on one or more vertical spires (maypole builders).

What are bowers? Bowers can be complex structures built by the males but are not used for nesting, only as a prelude to it. Bowers are generally associated with decorated display courts, and most species also decorate the structural components of their bowers. Without exception, they are built on the ground and act as a stage for the male courtship display. With their bowers, vocalizations, plumage and ritualized displays, bowerbirds have one of the most complex sets of display traits of any animal. Aspects of this intriguing behavior call be reasonably easily observed and photographed in areas of Queensland, Australia and are guaranteed to fascinate and entertain.

Avenue Builders

In the misty crests and hollows of the Lamington Range, several species of avenue building bowerbirds congregate. O'Reilly's Guesthouse, an eco-friendly complex at the end of the road and on the edge of the rainforest, is a recommended base for observing these species. Here you are greeted by a dawn chorus of 'whip-cracking' Whipbirds and meowing Catbirds and in the evening, the sun slides behind a craggy skyline with layer upon layer of variously blue-hued peaks in between. Crimson Rosellas and color-saturated Australian King Parrots mingle with the Lewin's Honeyeaters, Eastern Spinebills, Superb Blue Wrens, Golden Whistlers and Welcome Swallows around the settlement. As the evening light fades, out come the denizens of the night: Possums, Pademelons (a species of wallaby) and Sugar Gliders.

In the first light of morning, a number of pigeon-sized birds can be observed foraging in the meadows. These are male and female Satin Bowerbirds (Ptylinorhynchus violaceus). The male is a glossy blue-black with a violet eye and a semi-covered greenish-yellow bill. The female is a dull greenish and bluish grey with pale rufous wings, breast and a yellowish-white abdomen with darker scallops and blue eyes. The young males look superficially similar to females, and it takes a full seven years for them to acquire full male plumage. The bower consists of twigs painted with mixtures of berry-juice saliva and hoop pine leaves, tobacco bush berries and charcoal. The surrounding area is decorated mainly with blue items, often human-derived, as well as cicada cases, feathers, onion skins, flowers (blue and yellow) and berries. Dominant males gather sticks and ornaments from surrounding bowers including 'practice' structures made by immature males and defend them in order to gain the attention of passing females.

Intermingling with the Satin Bowerbirds are the fruit-eating Regent Bowerbirds (Sericulus chrysocephalus). The male of this species is a spectacular gold and black. The female is black-crowned with a scalloped back, yellow eye and black bill. This species exemplifies the inverse relationship between the intricacy of the display (and bower) and the spectacular nature of the plumage. The bright-plumed male Regent Bowerbird builds a scanty avenue often consisting of only a few twigs decorated with green berries, cicada shells and other objects often stolen from Satin Bowerbird bowers. Decorating objects are mainly yellow and orange, which makes an interesting comparison to the blue objects favored by the Satin Bowerbirds and the white objects favored by the Great Bowerbirds. The male will display when a female approaches his bower: prancing, twisting and prostrating himself, he will make good use of the bright yellow coloration and will also offer 'gifts' from his ornamental collection. Mating takes place in the bower, in other pre-cleared avenues or in adjacent branches.

Further along the Atherton Tableland, there were reports of a Great Bowerbird (Chlamydera nuchalis) romancing multiple females in his characteristic avenue-type bower. The well-constructed "bachelor pad" was located on the side of a small country road under a tree which hosted Cicada Birds, colorful Figbirds and Black-shouldered Kites resting after a hunting sortie. The relatively large Great Bowerbird sports rather a drab livery: grey head and breast without streaking or spotting. There is a crest of pink-lilac feathers, much reduced in females, that is hidden except during mating rituals. The bower was fastidiously constructed, complete with a 'roof.' The avenue, as well as the ground in front of the bower, consisted of a diverse array of objects with white being the dominant color: bleached snail shells, broken masonry, aluminum foil, sundry jewelry chains, stones, fruit, assorted ribbons, human hair ties and broken glass. Previous observations suggested that the favorite offerings to the female were aggregated near the entrance of the bower, and indeed this was the case in the bower under observation, as green fruit and shards of broken green glass were stashed by the left side of the entrance. This is thought to offer a contrasting color to the lilac crest and provide maximum visual impact. There was also a collection of pink ribbons in the same location. The custodian of this bower was very alert and fastidious. Every 10-12 minutes he would descend and do some housekeeping: shifting the shells, realigning the ribbons and draping the inside of the avenue with streamers of shredded paper. He would call from the bower entrance, from the ground around the bower and from the branches of an adjacent tree. He arrived one time accompanied by three females. Several of them scrutinized the bower from the branches before retiring. Later one female descended to the ground, the male strutted with lowered wings, picked up one of his green fruits and later the pink ribbon ...... she entered the bower from the back and observed his performance from within.... the male, satisfied she was impressed, slipped quickly around to the back entrance of the bower and mounted her. There was a flurry of feathers, a few squawks and the female shot out of the front entrance and disappeared into a nearby tree to reapply her 'makeup'. It was difficult to assess whether the mating was successful, but this was a prototypical maneuver by a male, avenue-type bowerbird.