Family CASUARIIDAE Kaup, 1847

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Introduction

Casuariidae (cassowaries and emus — large non-flying ratites) were recognised as a combined family for a relatively short period (Christidis & Boles 2008). Prior to this recognition two distinctive families were established (Casuariidae — cassowaries and Dromaiidae — emus). Even today there is conflict in the recognition of the partition (Marchant & Higgins 1990; Dickinson 2003) of the two, although DNA analysis and interpretation of the family has confirmed this amalgamation as part of the order Casuariiformes. This order was recently accepted as distinct from Struthioniformes (e.g. Christidis & Boles loc cit.) The family is centred in Australia with outlying members of the genus Casuarius occurring in New Guinea and some of its satellite islands. There are six species in two genera, four of which are Australian, albeit two now extinct. The subspecific status has been confused by the over-splitting of the group. Much remains to be done in this area of taxonomy.

Species of the Casuariidae are seen in either large gregarious flocks (emus) or as singles, pairs or small family groups (all species), vocalisation is generally restricted to communication between pairs and consists of loud drumming, especially in times of potential danger or possible nest predation. A varied habitat selection is apparent (forest, woodland, shrubland, grassland etc.; cassowaries tend to frequent heavily vegetated tropical forests, occasionally utilising adjacent open areas; emus utilise a variety of habitats ranging from forest to open grassland and herb field, from the arid interior to the coastal plains. All species are primarily omnivorous with the principal foods being of herbivorous nature.

The species exhibit polyandry, with emus maintaining pairs until breeding commences. Breeding behaviour varies within the two distinctive groups, the role of incubation and care of the young being conducted by the male alone. Pairs are not maintained. Females often mate with several males within a season; nesting occupies the cooler months (autumn and winter). A nest site consists of a slight depression sometimes with vegetation such as grass, twigs and/or leaves. The eggs are large and elliptical, being unmarked apart from the rare incidence of nest staining. The surface texture is rough and the base colour green; in cassowaries this is a pale green while in emus the colour deepens to a dark green and in some to almost black. Clutch sizes range upwards from four, larger clutches possibly indicating more than one female’s involvement. The young are precocial but dependant on the adult male for warmth and protection.

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General References

Christidis, L. & Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. Melbourne : CSIRO Publishing 288 pp. [57-58]

Dickinson, E.C. (ed.) 2003. The Howard & Moore Complete Checklist of the Birds of the World. London : Christopher Helm 1039 pp. [35]

Heupink, T.H., Huynen, L. & Lambert, D.M. 2011. Ancient DNA Suggests Dwarf and 'Giant' Emu are conspecific. PLoS ONE 6(4):e18728. doi:10.1371/journal.pone.0018728. pp. 7

Marchant, S. & Higgins, P. (coordinators) 1990. Handbook of Australian, New Zealand and Antarctic Birds. Melbourne : Oxford University Press Vol. 1 Pt A 735 pp. 53 pls. [47-67]

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