Richmond birdwing butterfly
Common name: Richmond birdwing
Scientific name: Ornithoptera richmondia
Family: Papilionidae (swallowtails)
Conservation status: This species is listed as Vulnerable in Queensland (Queensland Nature Conservation Act 1992). It is ranked as a critical priority under the department's Back on Track species prioritisation framework.
The Richmond birdwing is one of Australia's largest butterflies with a wingspan of up to 16 cm in females and 13 cm in males.
Males and females differ in appearance. Females have dark brown or black wings with extensive white, cream or, in the hindwing, yellowish markings. The upper forewing of males is black with a distinctive iridescent green leading edge, while the upper hindwing is predominantly iridescent green with black spots. The underside of the male's forewing is black with extensive green or blue-green markings whereas the hindwing is largely blue, green and yellow with obvious black spots.
Larvae develop through five stages (instars), moulting their skins between each stage. The mature (fifth instar) larvae can grow up to 58 mm long and are variable in colour, ranging from black to pale grey-brown. Larvae have a series of prominent, fleshy spines running along their outer dorsal (back or upper) surface and a similar but shorter row of spines along the outer ventral (lower) surface. The bright green or bluish-green chrysalis or pupa is 40 mm long. It bears a lateral projection and two small dorsal projections on the thorax.
The larvae are cannibalistic and usually solitary (although only one larva is typically found on an individual food plant, higher larval densities may occur in some situations, e.g. on planted vines in backyards).
Eggs are roughly spherical, approximately 2 mm in diameter and bright yellow or brownish-yellow. They are laid on the undersides of soft leaves of the food plant.
Habitat and distribution
The Richmond birdwing butterfly lives in subtropical rainforest where its larval host plants grow. Its distribution once extended from Maryborough in southern Queensland to Grafton in New South Wales. Today its distribution is fragmented, with the species occurring in two main areas: in the north from Cootharaba on the Sunshine Coast to near Caboolture and in the south, from Ormeau and Mount Tamborine in the Gold Coast hinterland to Wardell in north-east New South Wales. The Richmond birdwing occasionally occurs and breeds in the Brisbane area.
The Richmond birdwing lays eggs singly or in small clusters (up to three) on native Pararistolochia vines (P. praevenosa at low to moderate altitudes, i.e. <600 m, and P. laheyana at high altitudes, i.e. above about 600 m), on which the larvae are entirely dependent for food. The caterpillars only leave these plants to complete their development to pupal and then adult stages. The birdwing butterfly vine P. praevenosa is only patchily distributed and in low abundance.
Pararistolochia praevenosa is listed as Near Threatened under the Nature Conservation Act 1992 whereas P. laheyana is listed as Least Concern.
In 1870 the Richmond birdwing was reported as being abundant in the streets of Brisbane. Today, its rainforest habitat has been extensively cleared with less than one per cent of the original area still in existence. Permanent populations of the Richmond birdwing no longer exist in the Brisbane area. Similarly, habitat loss and fragmentation has caused the butterfly’s distribution to shrink back from its former northern and southern extents. As remnant colonies become isolated, the resulting inbreeding leads to a variety of negative effects, which may include reduced reproductive rate, the laying of sterile eggs, abnormal larval development, premature death, pupation failure, a reduction in size of adults and a loss of vigour, ultimately causing local extinction. The impacts of habitat loss, fragmentation and inbreeding are likely to be exacerbated by climate change.
While Richmond birdwings naturally lay eggs on the two native host plant species, they are also attracted to lay on the introduced Dutchman's pipe Aristolochia elegans. However, the leaves of this invasive vine are toxic and kill the larvae when they are eaten. The introduced Dutchman's pipe is common in gardens and as a weed in bushland, creating host plant confusion for egg-laying adult females and a 'death trap' for any larvae that hatch out.
In 2008, the department, along with David Fleay Wildlife Park and the active community group, the Richmond Birdwing Conservation Network (RBCN), began a joint project to help conserve the species using a captive breeding and release strategy. Under the breeding program, Richmond birdwings from geographically separate sources have been mated with the aim of producing more genetically diverse offspring. These captive-reared progeny have been reintroduced at selected sites to help restore wild populations. Following the first releases in 2010, evidence of natural breeding by the butterfly and more than a dozen flying adults were seen in the Kin Kin and Cootharaba areas of the Sunshine Coast for the first time in almost two decades. Since the program was initiated, more than 350 Richmond birdwing individuals, mostly larvae and pupae, have been reintroduced across nine sites in south-east Queensland.
This reintroduction program complements other important components of RBCN’s enthusiastic efforts to conserve the Richmond birdwing, namely the reinstatement of corridors and stepping stones of the food plant P. praevenosa to link existing remnant habitat and isolated butterfly populations, the removal of Dutchman’s pipe, and mapping of the current distribution of the butterfly and its food plant.