The white-browed treecreeper (''Climacteris affinis'') is the smallest of the Australo-papuan treecreepers and sole family member adapted to arid environments. The species foraging strategy involves climbing the trunks of trees in search of invertebrate prey on and under bark. Although some populations within the species range have declined, the species

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

conservation status is of

Least Concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

Taxonomy and evolution

The white-browed treecreeper (''Climacteris affinis'') is one of 7 species of Australo-Papuan endemic treecreepers (Family: Climacteridae). Prior to the development of molecular diagnostic techniques, the relationship of Climacteridae to other avian families was long debated.

Phylogenetic analysis In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

has since revealed the family to be most closely related to

bowerbird Bowerbirds () 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 ...

s and

catbird Several unrelated groups of songbirds are called catbirds because of their wailing calls, which resemble a cat's meowing. The genus name ''Ailuroedus'' likewise is from the Greek for "cat-singer" or "cat-voiced". Australasian catbirds are the ...

s (Family: Ptilonorhynchidae). Together these two families are thought to represent one of the most ancient linages of ‘

songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 500 ...

s’ (oscines, suborder Passeri), diverging early during the rise and radiation of

oscines A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5000 ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. The further split between Climacteridae and Ptilonorhynchidae is estimated to have occurred 58.7-35.2 million years ago. Within Climacteridae, two genera are recognised ''Climacteris'' and ''Cormobates''. Molecular analysis estimates the divergence between genera to have occurred during the

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

-early-

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

period. This estimate is further supported by the recovery of fossils referred to both genera within early

deposits in

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

, Australia. These ancient fossils all exhibit morphological features associated with

scansorial Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose num ...

(tree-trunk climbing), the primary mode of locomotion used during foraging by all extant species. The presence of these features suggest this foraging strategy to have evolved early within the family's evolutionary history. The genus name ‘''Climacteris''’ is derived from the Greek term meaning ‘the rung of a ladder’, and refers to the groups tree-trunk climbing habits. The species name ‘''affinis''’, Latin for 'allied', refers to the species resemblance to the

red-browed treecreeper The red-browed treecreeper (''Climacteris erythrops'') is a species of bird in the family Climacteridae. It is endemic to temperate and subtropical eastern Australia. It is found in mature eucalypt forests and woodlands in both coastal and mount ...

(''Climacteris erythrops'').

Subspecies

Two subspecies are recognised: * ''C. a. affinis'' Blyth, 1863 – Australia, east of

Spencer Gulf The Spencer Gulf is the westernmost and larger of two large inlets (the other being Gulf St Vincent) on the southern coast of Australia, in the state of South Australia, facing the Great Australian Bight. It spans from the Cape Catastrophe and ...

(rump uppertail coverts and tail grey) * ''C. a. superciliosus'' North, 1895 – Australia, west of Spencer Gulf (rump, uppertail coverts and tail brown)

Description and field identification

The white-browed treecreeper is 14–16 cm in length, has a wingspan of 22 cm and weighs 21gm. Adult male plumage is mostly dark grey above (crown, neck, rump and uppertail) excluding the mantle and scapulars of which are brown and black sub-terminal tail-band. Facial plumage includes black lores, white tapered eyebrow and black and white streaked ear-coverts. The chin is white and throat brownish grey. The upper breast is grey and lower breast, belly, flanks and vent streaked black and white. Undertail coverts are barred black and white. Females are similar to males but with rufous stripe bordering the upper edge of the eyebrow and dull white streaking, tinged rufous, on the centre of the upper breast. In both sexes the bill is black, around 1.5–2 cm long and is relatively straight and slender. The iris is dark brown and legs and feet black. Juveniles differ from adults with pale grey bill and both facial patterning and ear-covert streaking duller and less distinct. The white-browed treecreeper has moderately long wedge shaped wings and square tail. Flight pattern over longer distances is undulated, involving brief bursts of flapping within long glides, during which a buff wingbar is visible.

Similar species

The

brown treecreeper The brown treecreeper (''Climacteris picumnus'') is the largest Australasian treecreeper. The bird, endemic to eastern Australia, has a broad distribution, occupying areas from Cape York, Queensland, throughout New South Wales and Victoria to Po ...

(''Climacteris picumnus'') is similar in appearance to the white-browed treecreeper; however, the brown treecreeper's breast streaks are duller and ear-covert streaking confined to rear coverts. In addition, the brown treecreeper's short shrill ‘''peep''’ calls differ greatly to that of the white-browed treecreeper's long ‘''prrrpt''’ insect-like calls.

Distribution and habitat

White-browed treecreepers inhabit arid and semi-arid regions across southern Australia, excluding

Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...

. The two subspecies ranges do not overlap, ''C. a. affinis'' found east of the Spencer Gulf and ''C. a. superciliosus'' to the west. White-browed Treecreepers inhabit a range of woodland and shrubland communities, dominated by either ''

Acacia ''Acacia'', commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia. The genus na ...

Casuarina ''Casuarina'' is a genus of 17 tree species in the family Casuarinaceae, native to Australia, the Indian subcontinent, southeast Asia, islands of the western Pacific Ocean, and eastern Africa. It was once treated as the sole genus in the fami ...

'' or ''

Callitris ''Callitris'' is a genus of coniferous trees in the Cupressaceae (cypress family). There are 16 recognized species in the genus, of which 13 are native to Australia and the other three (''C. neocaledonica, C. sulcata'' and ''C. p ...

'' species, with both dense and open understory's. White-browed treecreepers are

sedentary Sedentary lifestyle is a lifestyle type, in which one is physically inactive and does little or no physical movement and or exercise. A person living a sedentary lifestyle is often sitting or lying down while engaged in an activity like soci ...

, pairs or groups actively defending relatively large territories (averaging 8.4

hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is a ...

s in some regions) throughout the year.

Ecology

Feeding

The white-browed treecreeper is a

(tree-trunk climbing) bark-foraging specialist, feeding upon a range of invertebrates (predominantly ants) gathered from on and beneath the bark of tree trunks and branches. The climbing technique employed by the species is described as ‘inching’ by which the lower foot is lifted and brought to the level of the upper foot prior to the upper being moved higher.Orenstein, Ronald. (1977). Morphological Adaptations for Bark Foraging in Australian Treecreepers (Aves: Climacteridae) (PhD). University of Michigan. Such a technique differs from some other

birds which lift their feet from the substrate simultaneously in a hopping or hitching fashion. Once white-browed treecreepers reach the uppermost portions of a tree they glide down to a lower position on a nearby tree to recommence climbing. The species also frequently forages on the ground among logs and leaf litter. White-browed treecreepers forage alone, in small family groups or during winter within mixed-species assemblages comprising other insectivores.

Feeding adaptations

White-browed treecreepers exhibit a number of morphological traits, primarily of the legs, feet and toes, thought to represent

bark-foraging

adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...

s. Such traits include increased toe length (increasing the span of the foot), long strongly curved claws (assisting the gripping of substrates), increased

syndactyly Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and diprotodontia, but is an unusual condition in humans. The term is from Greek σύν, ''syn'' 'together' and δάκ� ...

of the front toes and reduced pads on the sole of the foot (reducing contact of the plantar surface of the foot to the substrate). Additionally, ''Climacteris'' species are able to move the hind toe independently to that of the front toes due to a lack of some ligament within the foot. This enables finer adjustments of footings to be made.

Breeding

White-browed treecreepers' breeding season varies across its range, commencing as early as July in the western parts of its range to August in the east, and continuing until November. White-browed treecreepers breed both as unassisted simple pairs or in cooperatively breeding units consisting of a breeding pair and 1-3 male offspring from previous years. Non-breeding male ‘helpers’ provide assistance with all nesting related activities, other than incubation and brooding (conducted by the female alone). White-browed treecreepers build shallow saucer-shaped nests within tree hollows, made of bark fibres, grass, twigs and branchlets and line the nest with feathers, fur, vegetable down and wool. The female lays a clutch of 1-3 pinkish-white eggs speckled reddish and purplish-brown, which she incubates for 17–18 days. Nestlings take approximately 25–26 days to fledge upon which they remain dependent on their parents and associated ‘helpers’ for food for up to 37 days. Although up to two broods may be raised per season white-browed treecreepers have low productivity, with an average of only 1.58 young fledged per breeding unit annually.

Threats

Threats to the white-browed treecreeper include habitat loss and fragmentation due to land clearing. Such threats have resulted in population declines and range contractions within some regions including Victoria, Australia, within which the species is now listed as

Threatened Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensat ...

under state legislation. The white-browed treecreeper has also been recognised as a species highly exposed to the effects of

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

Conservation status

White-browed treecreepers are not listed as threatened on the Australian

Environment Protection and Biodiversity Conservation Act 1999 The ''Environment Protection and Biodiversity Conservation Act 1999'' (Cth) is an Act of the Parliament of Australia that provides a framework for protection of the Australian environment, including its biodiversity and its natural and cultu ...

. However, their conservation status varies from state to state within Australia. For example: * The white-browed treecreeper is listed as threatened on the Victorian

Flora and Fauna Guarantee Act (1988) The ''Flora and Fauna Guarantee Act 1988'', also known as the ''FFG Act'', is an act of the Victorian Government designed to protect species, genetic material and habitats, to prevent extinction and allow maximum genetic diversity within the Au ...

.Department of Sustainability and Environment, Victoria
/ref> Under this Act, an ''Action Statement'' for the recovery and future management of this species has been prepared.Department of Sustainability and Environment, Victoria
/ref> * On the 2007 advisory list of threatened vertebrate fauna in Victoria, the white-browed treecreeper is listed as vulnerable.

References

{{Taxonbar, from=Q549909

white-browed treecreeper The white-browed treecreeper (''Climacteris affinis'') is the smallest of the Australo-papuan treecreepers and sole family member adapted to arid environments. The species foraging strategy involves climbing the trunks of trees in search of inver ...

Endemic birds of Australia

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