Bowerbird

Bowerbirds (/ˈbaʊ.ərbɜːrd/) make up the bird family Ptilonorhynchidae. They are renowned for their unique courtship behaviour, where males build a structure and decorate it with sticks and brightly coloured objects in an attempt to attract a mate. The family has 20 species in eight genera. These are medium to large-sized passerines, ranging from the golden bowerbird at 22 centimetres (8.7 in) and 70 grams (2.5 oz) to the great bowerbird at 40 centimetres (16 in) and 230 grams (8.1 oz). Their diet consists mainly of fruit but may also include insects (especially for nestlings), flowers, nectar and leaves in some species. The satin and spotted bowerbirds are sometimes considered agricultural pests due to their habit of feeding on introduced fruit and vegetable crops and have occasionally been killed by affected orchardists. The bowerbirds have an Austro-Papuan distribution, with ten species endemic to New Guinea, eight endemic to Australia, and two found in both. Although their distribution is centered on the tropical regions of New Guinea and northern Australia, some species extend into central, western, and southeastern Australia. They occupy a range of different habitats, including rainforest, eucalyptus and acacia forest, and shrublands. The Ailuroedus catbirds are monogamous, with males raising chicks with their partner, but all other bowerbirds are polygynous, with the female building the nest and raising the young alone. These latter species are commonly dimorphic, with the female being more drab in color. Female bowerbirds build a nest by laying soft materials, such as leaves, ferns, and vine tendrils, on top of a loose foundation of sticks. All Papuan bowerbirds lay one egg, while Australian species lay one to three with laying intervals of two days. Bowerbird eggs are around twice the weight of those of most passerines of similar size – for instance eggs of the satin bowerbird weigh around 19 grams (0.67 oz) as against a calculated 10 grams (0.35 oz) for a passerine weighing 150 grams (5.3 oz). Eggs hatch after 19 to 24 days, depending on the species and are a plain cream color for catbirds and the tooth-billed bowerbird, but in other species possess brownish wavy lines similar to eggs of Australo-Papuan babblers. In accordance with their lengthy incubation periods, bowerbirds that lay more than one egg have asynchronous hatching, but siblicide has never been observed. Bowerbirds as a group have the longest life expectancy of any passerine family with significant banding studies. The two most studied species, the green catbird and satin bowerbird, have life expectancies of around eight to ten years and one satin bowerbird has been known to live for twenty-six years. For comparison, the common raven, the heaviest passerine species with significant banding records, has not been known to live longer than 21 years. The most notable characteristic of bowerbirds is their extraordinarily complex courtship and mating behaviour, where males build a bower to attract mates. There are two main types of bowers. Prionodura, Amblyornis, Scenopoeetes and Archiboldia bowerbirds build so-called maypole bowers, which are constructed by placing sticks around a sapling; in the former two species these bowers have a hut-like roof. Chlamydera, Sericulus and Ptilonorhynchus bowerbirds build an avenue type-bower made of two walls of vertically placed sticks. Ailuroedus catbirds are the only species which do not construct either bowers or display courts. In and around the bower, the male places a variety of brightly colored objects he has collected. These objects – usually different among each species – may include hundreds of shells, leaves, flowers, feathers, stones, berries, and even discarded plastic items, coins, nails, rifle shells, or pieces of glass. The males spend hours arranging this collection. Bowers within a species share a general form but do show significant variation, and the collection of objects reflects the biases of males of each species and its ability to procure items from the habitat, often stealing them from neighboring bowers. Several studies of different species have shown that colors of decorations males use on their bowers match the preferences of females. In addition to the bower construction and ornamentation, male birds perform involved courtship displays to attract the female. Research suggests the male adjusts his performance based on success and female response.