Rousserolle d'Australie

Taxonomie

The taxonomic classification of the family Sylviidae is unstable and requires further enquiry. At present, it includes Old World warblers, Old World babblers and allies, which comprises 680 species in 119 genera, a diverse group of small to medium passerine birds. Genus Acrocephalus sits within the subfamily Acrocephalinae, which encompasses 223 species in 36 genera. Within subfamily Acrocephalinae, the Australian reed warbler is recognised as belonging to a monophyletic group consisting of Palearctic and Australasian region species. However, recent mitochondrial DNA analysis infers that pacific reed warblers (Acrocephalus spp.) can be divided into two main clades; Micronesian (except Guam), two Polynesian, southern Marquesas and Australian species in one clade, and remaining Polynesian taxa in the other clade. This analysis results in dividing the main Pacific group into a Micronesian group and a Polynesian group. The closest relative of the Australian reed warbler was previously recognised as the Pitcairn reed warbler (Acrocephalus vaughani), endemic to South Polynesia. Most recent phylogenetic analysis, however, finds the closest relative to the Australian reed warbler is the Caroline reed warbler (Acrocephalus syrinx).<p>There are two recognised subspecies:

Nom scientifique

Acrocephalus australis

Autorité

(Gould, 1838)

Ordre

Passériformes

Famille

Acrocephalidae

Genre

Acrocephalus

Répartition et habitat

Australian reed warblers are found in a wide range of natural and man-made wetlands including fresh, brackish and saltwater environments. Dense vegetation with vertical structures such as reeds (Phragmites), reedmace (Typha) and rushes (Juncus) are frequented in breeding and non-breeding season and Australian reed warblers are often observed perched sideways midway along a reed stem. This species is occasionally observed in shrublands and riparian woodlands surrounding water bodies where it can be observed foraging.

Migration

Complete migrants

Comportement

This species forages mainly individually but sometimes in pairs, in dense vegetation on insects and spiders and occasionally molluscs and seeds. The Australian reed warbler forages amongst dense riparian vegetation and in surrounding shrubs and woodlands where it can be seen gleaning arthropods from vegetation. This species is also known to sometimes forage on open mud near reeds and rushes.<p>This species forms a socially monogamous seasonal breeding pair; nest building and chick feeding are carried out by the pair for the season. The same male and female pairings are not typically repeated in following seasons. Australian reed warblers are known to be polygynous/polyandrous and engage in extra-pair copulations. Unlike all other Acrocephalus species which are sedentary, the Australian reed warbler migrates seasonally. The Australian reed warbler migrates to Southwest and Southeast Australia to breed from overwinter grounds throughout Eastern and Northern Australia. Males arrive at the breeding grounds from July to August onwards. Breeding season is from October to December in south-eastern Australia and September to December in southern Australia. Both males and females build the nest; however, the females contribute more than the males. The nest is a deep cup (6.4 – 9 cm diameter and 7 – 18.5 cm height) made from dead and fresh vegetation usually supported by fresh and dead reed stems found between 30–200 cm off the ground or water surface. Incubation is carried out by the female for 13 – 15 days and clutch size is between 2 and 4 eggs. Chicks are fed by both the male and female in the nest for a period of 10–13 days and parents continue to feed fledglings outside the nest until they are more than 28 days old. Australian reed warblers have a nesting success of 58%, and nest predation is the major cause of nesting losses.<p>Males arrive at breeding sites before females to establish a breeding territory. During breeding season, it is believed that males use song to establish and defend their territories as well as to advertise their fitness to other males and to females. Males use song extensively throughout the breeding season and can be observed singing from a perched position on breeding ground reeds with their fore crown feathers raised and throat feathers puffed out whilst singing. Whilst males and females build the nest used for incubating eggs and raising chicks, males build a different type of nest structure during courtship. These nest-like structures lack the strength and shape to be suitable for eggs and chicks, and are constructed prior to breeding commencement. This behaviour and the resultant nest-like structure is believed to be driven by mate selection, as well as the selection of a breeding territory during the formation of breeding pairs.

Conservation

Tendance de la population

stable