Western gerygone | |
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Subspecies exsul | |
Scientific classification
![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Passeriformes |
Family: | Acanthizidae |
Genus: | Gerygone |
Species: | G. fusca
|
Binomial name | |
Gerygone fusca (
Gould, 1838)
| |
Subspecies [2] | |
| |
![]() | |
Distribution of the western gerygone: Lighter shaded area represents non-breeding migration. |
The western gerygone (Gerygone fusca) is a small, brownish-grey species of passerine bird, which is found in inland and south-west Australia. [3] It is an arboreal, insectivore of open forest, woodland and dry shrubland. [4] It is not currently threatened with extinction ( IUCN: Least Concern). [1]
The western gerygone is a member of the family Acanthizidae (Thornbills and Allies), which has been split from the family Pardalotidae (Pardalotes). [5]
It is a sister-species to the mangrove gerygone (Gerygone levigaster). [6] The close relationship of this phylogenetic pair is suggested by analyses of both morphological characteristics [7] and genetic loci. [8] Populations of a common ancestor of the two species are thought to have diverged after becoming fragmented by severe aridity during the Pleistocene. [9] These two species are now in secondary contact in the Carpentarian Basin, but occupy very different habitats and do not interbreed. [9]
The common name western gerygone and scientific name Gerygone fusca are recognized by the taxonomies of the International Ornithological Congress, [2] Clement's Checklist, [10] the Handbook of the Birds of the World [11] and Christidis and Boles. [12]
The western gerygone has plain, brownish-grey upperparts, with no prominent wing markings. [3] The underparts are whitish, with variable amounts of grey on the throat and breast. [3] The outer tail-feathers are conspicuously marked, with large, white patches at the base, a broad, blackish, subterminal tail band and white tips. [13]
It is usually found singly or in pairs, [14] in the mid to upper storey of trees and shrubs [4] and is often located by its characteristic, persistent song. [4] It can be very active when foraging. [15]
The western gerygone is similar in appearance to several other Australian gerygones, which don't usually share its habitat. [16] Its plumage can be distinguished from these species by the diagnostic large, white patches at base of its outer tail feathers. [3]
The western gerygone is the most widespread gerygone species and is endemic to Australia. [4] Its three subspecies show subtle differences in plumage and form geographically separate populations: [4]
Nomadic individuals may travel far beyond this species' regular geographic limits. [17]
Gerygone species are largely allopatric. [16] They are usually separated from each other by their geographic distribution, or by their preference for different habitats. [16] As it is the only gerygone of the Australian interior, the western gerygone does not overlap geographically with other gerygones throughout most of its range. [3]
There are two island populations. [9] Both are near Perth in Western Australia. [9] Rottnest Island was colonized by the western gerygone in the 1950s. [18] It was first observed on the island in 1955 and rapidly spread into all suitable habitat. [19] On nearby Garden Island, which is closer to the Australian mainland, the species has been present since European records began. [9]
The western gerygone occupies a wide range of wooded habitats. [9] These vary from open sclerophyll forests, dominated by a broad array of eucalyptus species, to sparse mallee and mulga shrublands. [9] It is often found along watercourses. [9] In elevated regions, it only occurs below 850 meters. [4]
Different populations of the western gerygone show different patterns of movement. [9] Those in south-western Western Australia are partial migrants. [9] They breed only in the south-west, but some individuals migrate inland or northwards during winter. [9] Populations in the Carpentarian Basin and on the Eyre Peninsula are sedentary. [9] Desert populations are partially nomadic, responding to inland rainfall. [9]
The western gerygone is insectivorous. [4] Its foraging techniques include probing into bark, gleaning from foliage, hovering outside foliage and aerial strikes from perches. [16] It may join other small birds in mixed-species feeding flocks. [15]
Breeding usually occurs between September and January, but has been recorded from August to March. [20] Courtship involves intricate chases between pairs. [4] Territories are maintained throughout the breeding season and territorial disputes involve agitated calls. [4] Males display by intensely fluttering their wings and tail, with their bodies tilted horizontally. [20]
The nest is a long, oval-shaped, pendent structure, with a hooded entrance near the top and a 'tail' at the bottom. [20] Both sexes build the nest. [20]
The clutch size is 2 or 3 eggs, (rarely 4). [4] The incubation period lasts 10–12 days, and only the female incubates. [20] The nestling period lasts 10–13 days, and both parents feed the nestlings. [20] Fledglings are fed by their parents for up to 15 days, until independence. [4]
The western gerygone's song is an irregular series of clear, high-pitched whistles, with a meandering melody. [3] Each note maintains a consistent pitch and there is a distinct change in pitch between notes. [19] Although the song isn't loud in volume, its persistence and distinctive tonal qualities are often recognizable from long distances. [4] Singing birds may turn their head in different directions with each note. [4]
Across different mainland populations, songs are fairly similar. [19] Singing is mostly confined to the breeding season and this species is far less conspicuous when it is not breeding. [4]
A distinct, new song has emerged in the western gerygone population which colonized Rottnest Island in the 1950s. [19] Unlike the mainland song, its notes are delivered in a strictly repeated melody. [19] (See sound files on right for comparison.) In 2003, it was estimated that more than a third of the western gerygones on Rottnest island sang the new song, including some individuals which sang both the new song and the typical mainland song. [19]
The island biogeography of birdsong is of interest to evolutionary biologists because of its relevance to speciation. [21] The novel western gerygone song on Rottnest Island is a notable example of both cultural innovation and cultural transmission by social learning. [19] It has occurred over a rapid period of time in a recently isolated population. [19] Sexual selection could eventually result in the typical, mainland western gerygone song on Rottnest Island being completely replaced with the novel song. [19] If secondary contact is subsequently established with the original, mainland population, breeding birds may no longer respond to each other's songs. [19] Behavioural reproductive isolation is a mechanism of evolutionary divergence. [22]
The western gerygone is common throughout much of its range, especially in Southwest Australia. [13] Extensive clearing of native vegetation in this region has led to a reduction in abundance. [23] Predation of western gerygones by feral cats is thought to be uncommon. [4]
The Australian inland reaches extremely high temperatures in summer. [24] Heat waves in these regions can result in sudden, dramatic, large-scale avian mortality events, with lasting ecological consequences. [24] The frequency of such events is predicted to increase dramatically in coming decades, due to climate change. This poses a threat to Australia's inland birds, potentially including some western gerygone populations. [24]
Despite a declining population trend, [1] the western gerygone's conservation status is categorized as least concern by the IUCN [1] and by most Australian state legislation. [25] This species occupies a wide variety of habitats across a large geographic range, [1] which encompasses numerous protected areas, including large, secure national parks. [26]
Western gerygone | |
---|---|
![]() | |
Subspecies exsul | |
Scientific classification
![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Passeriformes |
Family: | Acanthizidae |
Genus: | Gerygone |
Species: | G. fusca
|
Binomial name | |
Gerygone fusca (
Gould, 1838)
| |
Subspecies [2] | |
| |
![]() | |
Distribution of the western gerygone: Lighter shaded area represents non-breeding migration. |
The western gerygone (Gerygone fusca) is a small, brownish-grey species of passerine bird, which is found in inland and south-west Australia. [3] It is an arboreal, insectivore of open forest, woodland and dry shrubland. [4] It is not currently threatened with extinction ( IUCN: Least Concern). [1]
The western gerygone is a member of the family Acanthizidae (Thornbills and Allies), which has been split from the family Pardalotidae (Pardalotes). [5]
It is a sister-species to the mangrove gerygone (Gerygone levigaster). [6] The close relationship of this phylogenetic pair is suggested by analyses of both morphological characteristics [7] and genetic loci. [8] Populations of a common ancestor of the two species are thought to have diverged after becoming fragmented by severe aridity during the Pleistocene. [9] These two species are now in secondary contact in the Carpentarian Basin, but occupy very different habitats and do not interbreed. [9]
The common name western gerygone and scientific name Gerygone fusca are recognized by the taxonomies of the International Ornithological Congress, [2] Clement's Checklist, [10] the Handbook of the Birds of the World [11] and Christidis and Boles. [12]
The western gerygone has plain, brownish-grey upperparts, with no prominent wing markings. [3] The underparts are whitish, with variable amounts of grey on the throat and breast. [3] The outer tail-feathers are conspicuously marked, with large, white patches at the base, a broad, blackish, subterminal tail band and white tips. [13]
It is usually found singly or in pairs, [14] in the mid to upper storey of trees and shrubs [4] and is often located by its characteristic, persistent song. [4] It can be very active when foraging. [15]
The western gerygone is similar in appearance to several other Australian gerygones, which don't usually share its habitat. [16] Its plumage can be distinguished from these species by the diagnostic large, white patches at base of its outer tail feathers. [3]
The western gerygone is the most widespread gerygone species and is endemic to Australia. [4] Its three subspecies show subtle differences in plumage and form geographically separate populations: [4]
Nomadic individuals may travel far beyond this species' regular geographic limits. [17]
Gerygone species are largely allopatric. [16] They are usually separated from each other by their geographic distribution, or by their preference for different habitats. [16] As it is the only gerygone of the Australian interior, the western gerygone does not overlap geographically with other gerygones throughout most of its range. [3]
There are two island populations. [9] Both are near Perth in Western Australia. [9] Rottnest Island was colonized by the western gerygone in the 1950s. [18] It was first observed on the island in 1955 and rapidly spread into all suitable habitat. [19] On nearby Garden Island, which is closer to the Australian mainland, the species has been present since European records began. [9]
The western gerygone occupies a wide range of wooded habitats. [9] These vary from open sclerophyll forests, dominated by a broad array of eucalyptus species, to sparse mallee and mulga shrublands. [9] It is often found along watercourses. [9] In elevated regions, it only occurs below 850 meters. [4]
Different populations of the western gerygone show different patterns of movement. [9] Those in south-western Western Australia are partial migrants. [9] They breed only in the south-west, but some individuals migrate inland or northwards during winter. [9] Populations in the Carpentarian Basin and on the Eyre Peninsula are sedentary. [9] Desert populations are partially nomadic, responding to inland rainfall. [9]
The western gerygone is insectivorous. [4] Its foraging techniques include probing into bark, gleaning from foliage, hovering outside foliage and aerial strikes from perches. [16] It may join other small birds in mixed-species feeding flocks. [15]
Breeding usually occurs between September and January, but has been recorded from August to March. [20] Courtship involves intricate chases between pairs. [4] Territories are maintained throughout the breeding season and territorial disputes involve agitated calls. [4] Males display by intensely fluttering their wings and tail, with their bodies tilted horizontally. [20]
The nest is a long, oval-shaped, pendent structure, with a hooded entrance near the top and a 'tail' at the bottom. [20] Both sexes build the nest. [20]
The clutch size is 2 or 3 eggs, (rarely 4). [4] The incubation period lasts 10–12 days, and only the female incubates. [20] The nestling period lasts 10–13 days, and both parents feed the nestlings. [20] Fledglings are fed by their parents for up to 15 days, until independence. [4]
The western gerygone's song is an irregular series of clear, high-pitched whistles, with a meandering melody. [3] Each note maintains a consistent pitch and there is a distinct change in pitch between notes. [19] Although the song isn't loud in volume, its persistence and distinctive tonal qualities are often recognizable from long distances. [4] Singing birds may turn their head in different directions with each note. [4]
Across different mainland populations, songs are fairly similar. [19] Singing is mostly confined to the breeding season and this species is far less conspicuous when it is not breeding. [4]
A distinct, new song has emerged in the western gerygone population which colonized Rottnest Island in the 1950s. [19] Unlike the mainland song, its notes are delivered in a strictly repeated melody. [19] (See sound files on right for comparison.) In 2003, it was estimated that more than a third of the western gerygones on Rottnest island sang the new song, including some individuals which sang both the new song and the typical mainland song. [19]
The island biogeography of birdsong is of interest to evolutionary biologists because of its relevance to speciation. [21] The novel western gerygone song on Rottnest Island is a notable example of both cultural innovation and cultural transmission by social learning. [19] It has occurred over a rapid period of time in a recently isolated population. [19] Sexual selection could eventually result in the typical, mainland western gerygone song on Rottnest Island being completely replaced with the novel song. [19] If secondary contact is subsequently established with the original, mainland population, breeding birds may no longer respond to each other's songs. [19] Behavioural reproductive isolation is a mechanism of evolutionary divergence. [22]
The western gerygone is common throughout much of its range, especially in Southwest Australia. [13] Extensive clearing of native vegetation in this region has led to a reduction in abundance. [23] Predation of western gerygones by feral cats is thought to be uncommon. [4]
The Australian inland reaches extremely high temperatures in summer. [24] Heat waves in these regions can result in sudden, dramatic, large-scale avian mortality events, with lasting ecological consequences. [24] The frequency of such events is predicted to increase dramatically in coming decades, due to climate change. This poses a threat to Australia's inland birds, potentially including some western gerygone populations. [24]
Despite a declining population trend, [1] the western gerygone's conservation status is categorized as least concern by the IUCN [1] and by most Australian state legislation. [25] This species occupies a wide variety of habitats across a large geographic range, [1] which encompasses numerous protected areas, including large, secure national parks. [26]