Gibberbird

Description

The gibberbird has a distinctive visage which is characterized by a grey crown, yellow forehead, face and underbelly with a black to grey-brown rump. The bill is a dark brown to black with grey-brown feet. The iris of the eye is a distinguishing shade of bright yellow.

Unlike other chats, the gibberbird only has slight sexual dimorphisms between the male and female. Females differ very slightly and can sometimes be distinguished by more brown plumage, especially around the throat, face and neck. They can also have a heavier breast band and a generally duller appearance in comparison to the males.

Juveniles appear similar to adults, with a brown back, crown and wings, with a pale yellow throat.

The gibberbird is monomorphic in terms of length and weight. Generic measurements have been found to range from 125 to 130mm in length and 14 to 20g in weight.

Habitat

Giberbirds are often observed in sparsely vegetated stony deserts with a scattering of grasses such as; Astrebla and Enneapogon. As well as low chenopod shrubland, which is mainly dominated by plants species such as Sclerolaena and Atriplex on higher grounds. In the stony deserts north of South Australia, gbberbirds can often be encountered in low, open shrubland or grassland of Atriplex vesicaria, Frankenia Serpyllifolia and Astrebla pectinata.

Distribution

The gibberbird is endemic to Australia and is known to inhabit the sparsely vegetated stony regions of gibber desert areas in arid regions. This habitat can include very open shrub land or grasslands. The extent of distribution for the gibberbird has been denoted as the far central Northern Territory, south-west Queensland to north-west New South Wales and across the north-eastern region of South Australia. This species is particularly common on the sparsely vegetated stony plains of Lake Eyre basin, NSW and the adjoining regions.

The gibberbird is primarily a sedentary species with no records of migration patterns, however there has been some local movements outside of breeding season, assumedly for resource attainment, especially in times of drought or flood.

Threats and human interactions

It is possible that the gibberbird is one of the few species that has actually benefited from the introduction of stock, both through the modifications of its habitat and the increased availability of insect larvae during the winter season.

Diet

The gibberbird primarily feeds upon a range of invertebrates including spiders, caterpillars, moths, cicadas, grasshoppers and other insects. Gibberbirds are indiscriminate, opportunistic foragers and have been known to feed on blow fly larvae dropped from fly-blown sheep. These are obtained by turning over clay clods with their bill to expose the sheltering maggots. Smaller larvae are consumed whole while larger larvae are bashed on the ground several times before swallowing.

The majority of foraging occurs while walking on the ground but the will occasionally take to the air up to 1 meter above ground level while chasing flying insects. The gibberbird has also been observed running swiftly over short distances while chasing low flying insects.

Reproduction

The gibberbird has no set breeding period with nesting behaviour being observed year round, with particularly high incidences occurring after the first rains of the season.

The nest of the gibberbird is usually situated in a depression on bare ground or beside a clump of saltbush or grass. Usually the gibberbird will nest with other pairs, often within 90m of one another. If a nest is robbed, all pairs without eggs or without young will desert and seek out a new nesting site, regardless of the stage of their nest. Those with eggs or young will remain at the nest site.

The nest of the gibberbird is exceedingly deep (40 cm in depth, 60 cm in diameter), with the cup of the nest usually built into the ground and the rim extending above ground level.

Common nest materials include dried grass, twigs, bark and rootlets, but nests have also been observed to contain flower portions and anomalies such as horse hair or wool.

The average clutch size is between 2 and 4 eggs. Eggs are a pale pink to light flesh colour with reddish spots clustered around the larger end of the egg.

The gibberbird chicks are altricial, blind and naked upon hatching.

Voice

There is little information on the call of the gibberbird and further studies will need to be conducted to fill in the gaps of this species. However, from current studies it is known that the gibberbird has a sweet song that is thought to be utilised to call to a mate. This song has been described as ‘musical chatter’ and to hear it is a squeaky weet, weet, weet, projected during flight.

The alarm call of the gibberbird is a series of 5 or 6 high piercing notes which triggers nearby gibberbirds to seek shelter.

The display call of the gibberbird is a sharp whit-whit-whit performed during the ascending part of the display flight.