Family PACHYCEPHALIDAE Swainson, 1831

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• Pachycephalidae Swainson, 1831.

Introduction

Pachycephalidae, the family of whistlers, shrike-thrushes and their allies, have a core distribution in Australia and New Guinea. Many of the 60 known species in 12 genera occur from southern Asia, to the Philippines, though the Indonesian archipelago and into the south-west Pacific island chains. There is some endemicity in the Australian fauna which includes 16 species in four genera, representing 44 ultrataxa or 27% of the world species. The family occurs throughout the continent and has colonised many offshore islands.

Pachycephalids have adapted readily to a wide number of environmental situations and representatives of the group can be found in most habitats. Feeding is carried out through scansorial, arboreal and terrestrial activities. The birds are insectivorous and glean, pounce, probe and snatch their prey. Small groups are often encountered while solitary birds are not unknown. Many are migratory or nomadic whereas others are sedentary by nature.

The songs and calls of this family are both loud and melodious; the songs are generally the first indication of their arrival in southern regions. Nests of most species are coarsely woven, unadorned cups of twigs and bark wedged into the forks of trees or shrubs and crevices; the nest of the shrike-tit differs in being smooth and cobweb-walled and placed high within the canopy of tall trees. The two or three eggs vary between and within genera and are usually white or buff to pale brownish olive, they are blotched, spotted or dotted with reddish brown and/or greyish black.

Diagnosis

'In structure, whistlers and shrike-thrushes are corvoid, though one of the few corvoid families to vary in possessing Pocock's (1966) process "D" on the carpo-metacarpus: it is developed uniquely in the shrike-thrushes and shrike-tits but not others. At the head of the humerus there is a single trabeculated fossa, part of a wider depression there; the internal tuberosity is narrow and low, and the furrow for attachment of the dorsal arm of the M. humerotriceps well developed. The internasal septum is lightly and variably ossified, not as much as in monarchs (Dicruridae) but much more than in Australasian robins (Petroicidae), and nasal bars are slender except in Aleadryas and some species of Pitohui. The palatines are also generalised with narrow medial shelves and acute, nipple-like transpalatine processes, and maxillo-palatine processes are usually broad and flat; but the tip of the vomer is more variable, either simply rounded-truncate with up-curled margins or with small nipple-like horns (whistlers) or with large and up-curled compoundly-lobed horns (shrike-thrushes). Lacking lachrymals (except Rhagologus and Pitohui dichrous group), the etethmoid plate is large (and ventrally thickened in Aleadryas), with a broadly flared, laterally rounded wing reaching the jugal; bar, unlike that in the Australasian robins; the ectethmoid foramen is reduced to a single small aperture in the mesethmoid region because fusion between ectethmoid and frontal is so extensive. Temporal configuration is also characteristic, if divergent in several genera (Rhagologus, Pitohui). The fossa is usually rather small and oblately rounded (Pachycephala and Colluricincla), and its flanking processes attenuate, particularly the postorbital which is directed downwards to overhang the shorter zygomatic in Aelodryas, Oreoica and Falcunculus; in Eulacestoma the postorbital is shorter and projects forward.'

Diagnosis References

Pocock T.N. 1966. Contributions to the osteology of African birds. Ostrich Suppl. No. 6: 113-123

Schodde, R. & Mason, I.J. 1999. The Directory of Australian Birds : Passerines. A Taxonomic and Zoogeographic Atlas of the Biodiversity of Birds in Australia and its Territories. Collingwood, Australia : CSIRO Publishing x 851 pp.

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