Friday, February 17, 2012

WA Endemic Subspecies - An Annotated List: Part 2: The Pilbara and Arid Zone

This is the second of three checklists of bird species and subspecies endemic (or nearly so) to the state of Western Australia, featuring taxa of the Pilbara and arid zones of the state, an area more defined by what it is not – the heavily forested south-west or geologically distinct Kimberley – than what it is. This vast region comprises several geographic divisions, namely the Pilbara, Gascoyne, Mid West and Goldfields – but in biogeographic terms is usually treated as part of an even larger bioregion, the Eyrean Region covering most of central Australia,

At first glance the area seems poorly endowed with endemics. It contains only one WA endemic species, Dusky Gerygone, and even this is also found in the Kimberley. However a look at subspecies level reveals some interesting patterns of endemism:
* A cluster of subspecies centred on the Hamersley Ranges betrays their status as a drought refuge during ancient climatic fluctuations. Most notable here is the rock-loving race whitei of the Striated Grasswren, which remains a promising candidate for splitting as a full species.
* A long gap in the distribution of coastal mangroves along the length of 80 Mile Beach has apparently existed long enough to allows subspeciation in several mangrove-dwelling birds (Torresian Kingfisher, Dusky Gerygone, White-breasted Whistler), but interestingly not in others (Mangrove Golden Whistler, Yellow White-eye)
* The larger islands off the mid-west coast, namely the Abrolhos; Dirk Hartog, Bernier and Dorre Islands in the Shark Bay area; and Barrow Island, all support one or more endemic subspecies, many of them Vulnerable.
* Several endemic taxa inhabit the Nullarbor Plain, the greater part of which lies in Western Australia - most notably, Nullarbor Quail-thrush, which has very recently been resurrected as a full species.
* Finally, several species spanning the vast Eyrean interior have managed to diverge into eastern and western populations in the absence of any obvious barrier. Most important here is the recently split (and very nearly endemic) Western Quail-thrush (formerly race marginatum of Chestnut-breasted Quail-thrush), but also notably ‘Western’ Whiteface castaneiventris, which has diverged quite strongly from eastern birds despite continuous distribution across the interior.

For those that missed it, a handy 2-page checklist of WA endemics can be downloaded here.

Species endemic to WA – Pilbara and Arid Zone
Dusky Gerygone Gerygone tenebrosa christophori (also in Kimberley G. t. tenebrosa)

Species almost endemic to WA - Pilbara and Arid Zone (range extends into adjacent states)
Naretha Bluebonnet Northiella narethae
Western Quail-thrush Cinclosoma marginatum

Subspecies endemic to WA – Pilbara and Arid Zone
Spinifex Pigeon Geophaps plumifera ferruginea 
Peaceful Dove Geopelia striata clelandi 
Bar-shouldered Dove Geopelia humeralis headlandi
Blue-winged Kookaburra Dacelo leachii occidentalis
Torresian Kingfisher Todiramphus sordidus pilbara

Little Corella Cacatua sanguinea westralensis
  [Pheasant Coucal Centropus phasianinus highami

Western Bowerbird Chlamydera guttata carteri
Black-tailed Treecreeper Climacteris melanura wellsi
Striated Grasswren Amytornis striatus whitei*
Western [Thick-billed] Grasswren Amytornis textilis textilis
Rufous Fieldwren Calamanthus campestris rubiginosisC. c. wayensis
White-browed Scrubwren Sericornis frontalis balstoni

Weebill Smicrornis brevirostris ochragaster
Southern Whiteface Aphelocephala leucopsis castaneiventris
Australian Magpie Cracticus tibicen longirostris

Black-faced Cuckoo-Shrike Coracina novaehollandiae subpallida
Mangrove Golden Whistler Pachycephala melanura melanura  (also Kimberley)
White-breasted Whistler Pachycephala lanoides carnarvoni
Mangrove Robin Peneonanthe pulverulenta cinereiceps (also Kimberley)
Horsfield’s Bushlark Mirafra javanica woodwardi
Yellow White-eye Zosterops luteus balstoni (also Kimberley)

Subspecies endemic to WA – Midwest offshore islands
Painted Button-quail Turnix varius scintillans
Lesser Noddy Anous tenuirostris melanops

White-winged Fairy-wren Malurus leucopterus leucopterus, M. l. edouardi
Variegated Fairy-wren Malurus lamberti bernieri
Southern Emu-wren Stipiturus malachurus hartogi
Rufous Fieldwren Calamanthus campestris hartogi, C. c. dorrie 

Subspecies almost endemic to WA - Pilbara and Arid Zone (range extends into adjacent states)
Galah Eolophus roseicapilla roseicapilla

Naretha Bluebonnet Northiella narethae
White-plumed Honeyeater Lichenostomus penicillatus carteri

Notes on subspecies
[Except where stated, subspecies descriptions follow Schodde & Mason Directory of Australian Birds [1] (=S&M) for passerines, and Handbook of Australian, New Zealand and Antarctic Birds [2] (=HANZAB) for non-passerines]

Painted Button-quail (race scintillans)
Endemic to the Abrolhos Islands. Notably smaller; also plumage differences, with more white on the back, wings and belly. Vulnerable.

Lesser Noddy (race melanops)
The two recognised subspecies are widely separated (the nominate race breeds on Seychelles and Maldives), but physical differences are slight, mainly on measurements, though “said to be” lighter in plumage [2]. The subspecies breeding on Ashmore Reef is unknown but is probably also melanops. Vulnerable.

Spinifex Pigeon (race ferruginea
Red above and below, ie. lacks white belly and has only an indistinct black breastband. Johnstone & Storr [3] state that intermediate forms in the southern Kimberley “make it difficult to recognize subspecies”; they also describe an isolated population at Cape Range with paler plumage. Despite numerous clinal forms, HBW/BirdLife International controversially split this as a full species - see this dedicated blogpost on the topic.

Spinifex Pigeons of the Pilbara race ferruginea - note the completely rufous belly and indistinct dark breastband visible in the right-hand photo.

Peaceful Dove (race clelandi)
Overall larger and paler; slightly reddish/fawn cast to nape, back and scapulars. Disputed; recognised only as a “reddish form” by Johnstone & Storr [3] but retained as a subspecies by HANZAB.

Peaceful Dove of the clelandi population - sufficiently distinct to warrant subspecific recognition?

Bar-shouldered Dove (race headlandi)
Smaller, with pinker underparts and paler upperparts than nominate humeralis. Restricted to the Pilbara region, isolated from Kimberley populations by a break in distribution between Anna Plains and Cape Keraudren.

Galah (race roseicapilla)
Found all through the WA arid zone, but endemic to WA according to Johnstone & Storr [3]. Larger; generally paler but with a pink (not pale pink) crest; less of a ‘capped’ appearance; eye ring is whitish or grey and more warty or ‘crusty’ [2]. A fairly recent invader into the south-west of the state, still extending its range.

Galah, E. r. roseicapillus, at Sandstone in the mid-west.

Little Corella (race westralensis)
Found throughout the Pilbara and Gascoyne; more orange in the lores and neck feather bases, and possibly a more yellow underwing. A disputed taxon; HANZAB treats it as an isolated population of eastern form gymnopis, though recognising “some merit” in the split of westralensis.

Torresian Kingfisher (race pilbara)
Compared to the other Australian subspecies, pilbara is smaller; duller coloured (especially on the head); slightly smaller bill; thinner collar. 

Collared Kingfisher, race pilbara.

Blue-winged Kookaburra (race occidentalis)
A buff-breasted form; finer black streaks in the crown also give a much whiter cap. Restricted to the Hamersley region between Gascoyne and De Grey rivers [5].

Blue-winged Kookaburra, race cliftoni - note the relatively fine dark streaking on the crown, giving the bird a paler-headed appearance. 

  [Pheasant Coucal (race highami)]
A disputed taxon, “tentatively recognised as a large subspecies” by Storr [6], but not by HANZAB. Worth mentioning here because it is restricted in range (Pilbara coast and watercourses between Ashburton to De Grey Rivers) and probably declining.

Black-tailed Treecreeper (race wellsi)
“Allied Treecreeper”
This distinct Pilbara form is slightly smaller; more rufous on the breast (especially females); more white barring on the undertail coverts.

Western Grasswren (race textilis) [Thick-billed Grasswren (race textilis)]
Larger; darker brown above, paler below; and a longer tail compared to modestus. The taxonomy is “unsettled” according to Schodde & Mason, but two 2010 studies appear to confirm from both morphometrics [7] and DNA [8] that textilis and modestus should be split, a change already adopted by the IOC. Thus the Shark Bay population will become the nominate form of ‘Western Grasswren’ when textilis and myall (found in SA) are split from the much duller plumaged modestus, which will retain the Thick-billed name. Vulnerable; much-reduced from its historic range.

Striated Grasswren (race whitei)
“Rufous Grasswren”
Probably the next grasswren split to watch after Thick-billed/Western, and already split by Clements/eBird in 2016. Larger and richer chestnut-red over the dorsum, and rich buff (not cream) on the flanks; females also have a diffuse rufous wash instead of the typical chestnut patch (the ‘sexual mark’) on the flanks. Its distribution abruptly abuts that of nominate striatus, but whitei is ecologically restricted to stony spinifex-covered hillsides, while striatus lives on the sandplain heaths below. Nominate striatus grades very broadly between two forms, a browner south-eastern mallee form and a rufous (but still white-bellied) central sandplain form approaching whitei in colour but not size, actually grading smaller towards the northwest. A large genetic study of grasswrens [8] found that the rufous inland form of striatus is surprisingly genetically distinct given the broad ecophenotypic gradient, enough to justify its reinstatement as subspecies oweni. Rather annoyingly, molecular studies to date have not included whitei, which for the moment remains a tantalisingly likely future split.

White-winged Fairy-wren (races leucopterus and edouardi)
“Black-and-white Fairy-wren”
A distinctive black and white form exists on two islands separated by over 500km: leucopterus on Dirk Hartog Is. off Shark Bay (which due to a quirk of history is actually the nominate race), and edouardi on Barrow Is. The forms are distinct (eg. longer tail on female  leucopterus; cinnamon tinge in female edouardi), suggesting they possibly evolved independently, though the alternative (that they are survivors from an extinct black and white mainland race) has been discussed. Both forms are listed as Vulnerable. There have anecdotal reports of black & white forms on the mainland adjacent to Dirk Hartog Island, but these have never been substantiated, as all specimens have shown them to be only deep blue-black [9]. Rod Smith also reported melanistic mainland birds at Red Bluff near Kalbarri [10].

Variegated Fairy-wren (race bernieri)
An isolated form from Bernier Island near Shark Bay. Darker blue-violet head on males compared to birds from the adjacent mainland and Dirk Hartog Island. Vulnerable.

Southern Emu-wren (race hartogi)
A smaller, paler (greyer and reduced streaking) island form from Dirk Hartog. Also distinct for its much paler blue chest, lighter flanks, and less bold black streaking on the crown [5]. Vulnerable.

White-browed Scrubwren (race balstoni)
Has a much more finely ‘spotted’ breast and paler flanks than maculatus. Coastal distribution south to about Jurien Bay, beyond which some intergradation (ie. pigmented underparts) with maculatus occurs.

Rufous Fieldwren (races rubiginosis, wayensis, hartogi and dorrie)
A number of subspecies are endemic to the mid-west: west coastal form rubiginosis is much redder than south-western C. (c.) montanellus, especially over the crown and dorsum; inland form wayensis, found on salt lakes between Meekatharra-Sandstone and the Great Sandy Desert, also has bright rufous crown but lacks streaking. Distinct island subspecies also occur on Dirk Hartog (smaller, paler) and Dorre (longer tarsus) Islands; both are listed as Vulnerable.

Approximate distributions of the WA races of Rufous Fieldwren, Calamanthus campestris. The south-west form montanellus is treated as a separate species (Western Fieldwren) by some authorities, notably the IOC (after Schodde & Mason).

Weebill (race ochragaster)
A ‘pallid’ form, noticibly lighter than southern or Kimberley birds. Lacks fine streaking on the throat. Intergrades with the southern form around the upper Murchison.

Dusky Gerygone (race christophori [also in Kimberley G. t. tenebrosa])
An endemic WA species with two separated subspecies; christophori is larger and has a more russet cast to the back compared to the Kimberley form.

Southern Whiteface (race castaneiventris)
“Western Whiteface”
Paler brown, with a whiter throat, forehead and breast, but richly rufous flanks.

White-plumed Honeyeater (race carteri)
Both WA subspecies are yellower than eastern birds, particularly carteri which has a canary yellow face and bright yellow underwing coverts.

White-plumed Honeyeater, race carteri, showing the yellower face characteristic of western birds.

Western Quail-thrush [Chestnut-breasted Quail-thrush (race marginatum)]
Recently split as a separate species by the IOC list on the basis of convincing molecular work [11], C. (c.) marginatum is richer rufous generally; the male’s back is the same rufous colour as the breast; females have a greyer breast. Range extends approximately to the NT/SA/WA border so virtually endemic to WA.

Western Quail-thrush, photographed on Kirkalocka Station. Until recently included within Chestnut-breasted Quail-thrush, recent work indicates the western race warrants recognition as a separate species.

Black-faced Cuckoo-shrike (race subpallida)
A very pale form, with a silvery grey back and whitish belly. 

Mangrove Golden Whistler (race melanura [also Kimberley])
Males of this subspecies have a narrower dorsal collar and breast band, but it is more distinct for the females, which have a white not golden belly. 

White-breasted Whistler (race carnarvoni)
Both WA forms are larger than NT birds and have a broader chestnut collar. Compared to lanioides of the Kimberley, carnarvoni has greyer tail coverts and the female is browner/buffier with little yellow on the breast. Ranges from just south of Carnarvon to the start of Eighty Mile Beach.

Female White-breasted Whistler, race carnarvoni.

Australian Magpie (race longirostris)
A small, ‘black-backed’ form with a proportionally long, slender bill; the ‘thighs’ are white. The eggs have “spottings…instead of streakings or smears in the Western Magpie [dorsalis]” [9]. Confined to the Pilbara and possibly the edges of the Kimberley (Broome); intergrades with dorsalis through the Murchison region. 

Mangrove Robin (race cinereiceps [also Kimberley])
Smaller and paler, with less black on the lores. Taxonomy at subspecies level is “unresolved”[1].

Western Bowerbird (race carteri)
A smaller and more richly russet form, darker particularly in the underbelly [5]. It is restricted to narrow gullies in hillsides of the Cape Range NP, though there is some evidence of intergradation in historical skins of adjacent guttata. Interestingly the remaining Pilbara and centralian populations of this species, both guttata, have only minor differences despite considerable isolation across the Simpson Desert. 

Horsfield’s Bushlark (race woodwardi)
A plain rufous form, ie. cinnamon-coloured with only fine dark streaking. The colour is reported to be influenced by adaptation to the colour of the local soil, hence is unsurprisingly reddest here in the iron-rich Pilbara.

Yellow White-eye (race balstoni [also Kimberley])
The validity of Yellow White-eye subspecies “has been questioned”, but DNA studies have confirmed the eastern and western forms to be sufficiently distinct. This western form, which extends a little way around the Kimberley coast, has the same plumage but is overall duller, and smaller-billed. An unrecognised greyish variant is also reported to occur around Dampier-Port Hedland. 

[1] Schodde R & Mason I (1999) The Directory of Australian Birds: Passerines. A taxonomic and zoogeographic atlas of the biodiversity of birds of Australia and its territories. CSIRO Publishing.
[2] Marchant S. & Higgins PJ, et al. (eds) (1990-2006). Handbook of Australian, New Zealand and Antarctic Birds. (7 vols). Oxford University Press, Melbourne.
[3] Johnstone RE and Storr GM (1998-2004). Handbook of Western Australian birds (2 vols). Perth, Western Australian Museum.
[4] Christidis L & Boles WE (2008). Systematics and Taxonomy of Australian Birds. CSIRO Publishing, Canberra.
[5] Nevill S (2008). Birds of the Greater South West Western Australia. Simon Neville Publications.
[6] GM Storr (1984) Birds of the Pilbara Region, Western Australia. Records of the WA Museum, suppl 16.
[7] Black AB et al. (2010). A taxonomic framework for interpreting evolution within the Amytornis textilis-modestus complex of grasswrens. Emu 110: 358-363
[8] Christidis L et al. (2010). Plumage patterns are good indicators of taxonomic diversity, but not of phylogenetic affinities, in Australian grasswrens. Amytornis (Aves: Maluridae). Molecular Phylogenetics and Evolution 57: 868-877
[9] Serventy DL & Whittell HM (1976). Birds of Western Australia. Perth: University of Western Australia Press.
[10] Smith R (1989). Melanistic tendencies of White-winged Fairy-wren. Western Australian Bird Notes 49, March 1989.
[11] Toon A et al. (2012). Evolution of arid zone birds in Australia: Leapfrog distribution patterns and mesic-arid connections in quail-thrush (Cinclosoma, Cinclosomatidae). Molecular Phylogenetics and Evolution 62: 286-295.

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