Richmond Birdwing butterfly: knowledge of ecology aides recovery

The male Richmond Birdwing butterfly, on the way back from local extinction thanks to ecological knowledge and community work (Image: Dr Don Sands)

The Richmond Birdwing butterfly (Ornithoptera richmondia) is one of Australia’s biggest and most spectacular butterflies. Just 100 years ago, these butterflies were abundant throughout greater Brisbane.

Today they are gone. Not entirely extinct, but no longer in Brisbane. The reason is more than just building a city. It’s a story of habitat loss, isolation and invasive species.

We can give them the chance to return and we’ll explain how here.

Female Richmond Birdwing butterflies are large butterflies. They have a 15 cm (6 inches)  wingspan and the males 13 cm (5 inches). Like many species in nature, they are sexually dimorphic – the boys look different to the girls (there are complex reasons for this which we will cover in a later article). They are different sizes and strikingly different colours.

The males have beautiful and iridescent green hind wings. Their forewings are jet black with a striking iridescent green leading-edge. The females are drab, dark grey or brown wings – no fancy bits! It’s obvious who is screaming, “Hey babe I’m over here”.

Many birds also exhibit sexual dimorphism and it’s often the males which are the more colourful.

Healthy Richmond Birdwing populations used to be found from Grafton in New South Wales to Maryborough in southern Queensland. Unfortunately this butterfly is now listed as vulnerable (Nature Conservation Act 1992). It can only be found in two areas: between Caboolture and Kin Kin in Queensland, and Nerang and Wardell in New South Wales. Having fragmented, isolated, small populations doesn’t help their genetic diversity, and some colonies are inbreeding – the result is sterile eggs. Inbreeding in the wild really does matter (thanks to conservationbytes.com for that one!).

The Richmond Birdwing is fussy about where it lays its eggs. It prefers the native vines Pararistolochia praevenosa and P. laheyana and will lay no more than three round, green-yellow eggs. When they hatch the caterpillars battle with each other to the death, leaving only one victor per vine. The victor will feed on the vine until they pupate and metamorphose into adult Richmond Birdwing butterflies to start the cycle over again.

The Richmond Birdwing vine is the native vine on which the Richmond Birdwing butterfly lays its eggs (Image: Dr Don Sands)

The vines and the butterflies have a close ecological relationship however, vines are often considered weedy things and land clearing for farming and urban development has meant the removal of the vine. Both vine species, which are vital for the butterfly, are now listed as rare (Nature Conservation Act 1992). Rarity of course contributes to the isolation and subsequent decline of Richmond Birdwing populations.

As if isolation and loss of breeding habitat are not enough, the Richmond Birdwing also contends with an invasive vine species – the Dutchman’s pipe (Aristolochia elegans).

What’s the problem here?

This introduced weed looks so similar to the native vines that it fools the Richmond Birdwing into laying its eggs on the weed. Unfortunately the leaves are toxic and kill the caterpillars when they hatch. It’s triple whammy!

The invasive and toxic Dutchman’s pipe vine. The butterflies mistake this for their preferred native vine. (Image: Dr Don Sands)

This is a classic example of how the clearance of native habitat for human development, and the introduction of exotic plants can lead to the demise of native species and the alteration of native ecosystems.

Thankfully an increasing awareness of Australia’s ecology (and possibly because of the Richmond Birdwing’s beauty) has empowered community action. Community groups, such as the Richmond Birdwing Recovery Network, and schools are organising replanting programs. Starting with habitat restoration they are removing introduced Dutchman’s pipe and planting the native vines. This will help connect isolated populations, restore gene flow and increase the supply of food plants.

You can also contribute to restoring southeast Queensland’s ecology by planting the Birdwing’s native habitat vines in your backyard. Imagine seeing one of Australia’s biggest and most beautiful butterflies, or showing your children how it develops in your own backyard!

Try asking your local garden centre for the Richmond Birdwing vine (Pararistolochia. praevenosa and P. laheyana). Alternatively, subscribe to the TalkingNature.com e-mail list (opposite the butterfly, on the right towards the top of this page) or RSS feed for updates because we will be trying to distribute some of these seeds soon.

References

Queensland Environment and Resource Management

Queensland Museum