BIRD FAMILIES OF THE WORLD
 
 
a web page by Don Roberson
 
 
WHISTLERS & ALLIES Pachycephalidae
Whistlers, shrike-thrushes, shrike-tit, and allies
  • 52 species in Australasia
  • DR personal total: 24 species (46%), 4 photo'd

The Pachycephalidae are a diverse family of landbirds within Australasia. Genetic analysis is on-going, and the parameters of this family has been very unstable in recent years. For example, Crested Shrike-tit of Australia (left in a dramatic photo by Trevor Quested) is a distinctive bird with isolated populations frequenting open woodlands in east, southwest, and north Australia, has variously been considered a pachycephalid or a member of its own family, the Falcunculidae [Wattled Ploughbill Eulacestoma nigropectus of New Guinea has sometimes been assigned as a close relative in that family's brief existence]. The relationship of the shrike-tit was settled by Norman et al. (2009); using nuclear DNA they found it to be sister lineage to the core pachycephalids. So it is a whistler.

Not only has the family level assignment been debatable, but whether Shrike-tit is one species (as accepted by Sibley & Monroe 1990 and most field guides, e.g., Simpson & Day 1996, Morcombe 2000) or three species (adopted by Schodde & Mason 1999 and Dickinson 2003) is also an open question. The three groups differ in size, back color, and underpart pattern. In all three, males have black throats and females olive-green. Our headline photo is of a female.

Although colorful, Crested Shrike-tits can be unobtrusive. Singles or small family parties forage mostly high in the canopy and can be easily overlooked unless their calls — a soft, piping, mournful whistle — are learned [Simpson & Day 1996 suggest the pneumonic 'knock-at-the-door']. Sometimes their presence is revealed by the sound of tearing bark. Morcombe (2000) writes: "The function of the heavily built, deep bill is soon apparent if one of these birds is observed foraging. Strong pieces of bark are levered up by sliding the bill under, then rotating head and body to exert a twisting force through the flat blade of the bill." In this manner hidden insects and grubs are uncovered.

The "core" pachycephalids are the genus Pachycephalus — 39 species of whistlers — and the genus Colluricincla, 7 species of shrike-thrushes. Norman et al. (2009) found that these genera were paraphyletic. Two of the Pitohuis — Rusty Pitohui "P." ferrugineus and White-bellied Pitohui "P." incertus — should be moved to genus Pachycephalus, and so should the Morningbird of Palau, "Colluricincla" tenebrosa. Such changes would give us 42 species of Pachycephalus whistlers.

Pachycephalus whistlers are primarily forest birds in the mid or upper canopy, ranging from dull species to some bright ones, such as Golden Whistler (right), a widespread bird of many subspecies across Australasia and southwestern Oceania (this photo is from southwest Australia).

Whistlers have adapted to a wide variety of woodlands. The two pitohuis just mentioned, plus Black Pitohui "P." [=Melanorectes] nigrescens, are birds of thick tropical jungles in New Guinea (the first two in steamy lowlands, the Black in montane cloud forests). Gilbert Whistler (left) is a specialty of dry gum eucalypt woodlands of southern Australia. Island Whistler P. phaionotus inhabits mangrove swamps in the Moluccas and west Papuan islands; Vogelkop Whistler P. meyeri exists only in high montane forests in the Vogelkop Mountains on western New Guinea. Quite a number of whistlers are local endemics to remote mountains or south sea islands. This is a group that has diverged and filled many niches across Australasia and southern Oceania.

Many whistlers are much more easily heard than seen, and this can be especially true of the Colluricincla shrike-thrushes of Australia and New Guinea. Some are found in thick jungle; others, like Sandstone Shrike-Thrush C. woodwardi, are confined to arid sandstone cliffs in north-central Australia. The impressive vocalization of Grey Shrike-Thrush (right) are a common sound in Australian woodlands, but getting views (or photos!) can often be a challenge. This photo actually catches one in mid-song.

One of the most impressive attributes of some whistlers is the presence of a poisonous toxin in their skin and feathers. A powerful neurotoxin, chemically similar to that found in Central American poison dart frogs, is present and has long been known to native peoples in New Guinea, who avoid eating pitohuis. Dumbacher et al. (2008) found that the presence of neurotoxic alkaloids has evolved several times in New Guinea birds, and it may even be widespread in corvoid birds (Jønsson et al. 2008). It appears most potent in the true Pitohuis — Variable Pitohui P. kirhocephalus and Hooded Pitohui P. dichrous, which now have proven to be closely related to Old World oriole [Oriolidae]. They have evolved conspicuously orange-and-black plumage as a warning, similar to patterns of colorful "warning" evolved in Monarch butterflies. There are now questions as to whether other birds have evolved Müllerian mimicry in response (Dumbacher & Fleischer 2001).

The toxins come from eating poisonous melyrid beetles (Choresine), and the toxins are stored in the skin and feathers. They have been detected in Black "Pitohui" and in Rusty "Pitohui," which are not true pitohuis but are whistlers; in Rufous Shrike-Thrush Colluricincla megarhyncha of New Guinea; and in Blue-capped Ifriti Ifrita kowaldi, a New Guinea endemic that is not within the whistler family (Dumbacher et al. 2008, Norman et al. 2009).

The full outlines of the Whistler family is not yet known. Some have recently thought Wattled Ploughbill Eulacestoma nigropectus was closely related to Shrike-tit, and even separated out these two genera as their own family Falcunculidae (Dickinson 2003) but the most recent molecular evidence does not support this hypothesis (Norman et al. 2009). Where the unique Wattled Ploughbill goes in the big scheme of things is still not certain.

In contrast, the new evidence suggests that Crested Bellbird Oreoica gutturalis of Australia, plus Crested Pitohui "Pitohui" [=Ornorectes] cristatus and Rufous-naped Whistler Aleadryas rufinucha are closely related and are not within the Pachycephalidae (Norman et al. 2009). They are tentatively assigned to a new family, the Oreoicaeda.

We now know that Mottled "Whistler" Rhagologus leucostigma of New Guinea is not a whistler, but is within a clade that includes woodswallows and African bush-shrikes, but its exact position is not yet known (Norman et al. 2009). More dramatically, Olive-flanked "Whistler" Hylocitrea bonensis of montane Sulawesi is not a whistler, but is a member of the bombycillid radiation — it is related to waxwings, Palmchat and Hypocolius (Spellman 2008) — and is current best placed in its own family.

And then there are still mysteries. Is the unique New Zealand genus Mohoua — the species Whitehead, Yellowhead, and Pipipi — among the whistlers? Or should it be considered yet another new family? This is not currently known. Norman et al. (2009) found Mohoua to "have no obvious links to any pachycephaline genera" but beyond that the relationships are muddy. The same goes for the New Guinea genus Daphoenositta (Pink-faced "Nuthatch"). There remains much to learn about the whistlers and their allies.


Photos: Trevor Quested photographed the Crested Shrike-tit Falcunculus frontatus on Mt Wilson, New South Wales, Australia in March 2004. The Golden Whistler Pachycephala pectoralis was in Dryandra Forest, Western Australia, on 4 Aug 2008. The Gilbert's Whistler Pachycephala inornata was on Gulpa Island, New South Wales, Australia, on 31 Dec 1997. The Gray Shrike-Thrush Colluricincla harmonica was at the Stirling Range Resort, Western Australia, on 11 Aug 2008. All photos © Don Roberson, except the Shrike-tit © Trevor Quested and used with permission; all rights reserved.

More photos by Trevor Quested can be seen on his website.

Bibliographic note: There is no "family book" covering the Pachycephalidae, but good photographs and information about Australian and New Guinea species are found in Frith (1979) and Coates (1990), respectively.

Literature cited:

Barker, F.K., A. Cibois, P. Schikler, J. Feinstein, and J. Cracraft. 2004. Phylogeny and diversification of the largest avian radiation. Proc. Nat. Acad. Sci. 101: 11040-11045.

Coates, B.J. 1990. The Birds of Papua New Guinea. Part II. Dove Publ., Ltd., Alderley, Australia.

Dickinson, E.C., ed. 2003. The Howard & Moore Complete Checklist of the Birds of the World. 3d ed. Princeton Univ. Press, Princeton, N.J.

Dumbacher, J.P., K. Deiner, L. Thomposn, and R.C. Fleisher. 2008. Phylogeny of the avian genus Pitohui and the evolution of toxicity in birds. Molec. Phylog. Evolv. 49: 774–781.

Dumbacher, J.P., and R.C. Fleischer. 2001. Phylogenetic evidence for colour pattern convergence in toxic pitohuis. Müllerian mimicry in bird? Proc. R. Soc. Lond. B 268: 1971–1976.

Jønsson, K.A., R.C.K. Bowie, J.A. Norman, L. Christidis, and J. Fjeldså. 2008. Polyphyletic origin of toxic Phiohui birds suggests widespread occurrence of toxicity in corvoid birds. Biol. Lett. 4: 71–74.

Frith, H. J., consulting ed. 1979. The Reader's Digest Complete Book of Australian Birds. 2d revised ed. Reader's Digest Services, Ltd., Sydney.

Morcombe, M. 2000. Field Guide to Australian Birds. Steve Parish Publ., Archerfield, Australia.

Norman, J.A., P.G.P. Ericson, K.A. Jønsson, J. Fjeldså, and L. Christidis. 2009. A multi-gene phylogeny reveals novel relationships for aberrant genera of Australo-Papuan core Corvoidea and polyphyly of the Pachycephalidae and Psophodidae (Aves: Passeriformes). Molec. Phylog. Evol. 52: 488-497.

Schodde, R., and I.J. Mason. 1999. Directory of Australian Birds. Passerines: i-x, 1-851. CSIRO Publishing, Canberra.

Sibley, C.G., and J.E. Ahlquist. 1990. Phylogeny and Classification of Birds: A Study in Molecular Evolution. Yale Univ. Press, New Haven, CT.

Sibley, C. G., and B.L. Monroe, Jr. 1990. Distribution and Taxonomy of Birds of the World. Yale Univ. Press, New Haven, CT.

Simpson, K., and N. Day 1996. Field Guide of the Birds of Australia. 5th ed. Viking, Victoria, Australia.

Spellman, G.M., A. Cibois, R.G. Moyle, K. Winker, and F.K. Barker. 2008. Clarifying the systematics of an enigmatic avian lineage: what is a bombycillid? Molec. Phylog. Evol. 49: 1036-1040.

 
 

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