Richmond birdwing

A hand-span of black, gold and iridescent green, the Richmond birdwing is one of Australia’s largest butterflies and, for all that glamour, a rainforest animal through and through: the hostage of a single plant. Its caterpillars can eat the leaves of essentially one species — a native rainforest climber called the birdwing vine, Pararistolochia praevenosa — that threads up through the lowland and hinterland scrubs the butterfly haunts. Where the vine grows, the great butterfly can breed. Where it doesn’t, it cannot, because a caterpillar that eats a single plant cannot follow the forest anywhere the vine has not gone.

The specialist’s bargain, worn on the sleeve: a whole magnificent insect staked on one thread it cannot do without. So when the lowland scrub was felled, the vine went with it and the butterfly’s range fell away in step, the splendid thing undone by the loss of a climber most people would never have noticed threading through the tangle overhead.

Then came a crueller turn. Dutchman’s pipe (Aristolochia littoralis, once sold as A. elegans), a South American climber widely planted in gardens for its curious flowers, looks and smells enough like the real birdwing vine to fool an egg-laying female into settling on it. Its leaves are poison to the caterpillars, which hatch onto a plant that kills them. So across the cleared country the birdwing faced two blows at once: its one food plant disappearing, and a lethal impostor taking the eggs it still managed to lay, emptying the butterfly’s future one clutch at a time.

The way back turned the problem on its head. Nobody saved the Richmond birdwing by mass-rearing butterflies and letting them go; that would only have loosed more insects into country that still could not feed them. The effort went into the vine instead: propagating and planting Pararistolochia praevenosa back across its old range, through gardens and schoolyards, along farm fences and roadside gullies and remnant creeks, knitting the food plants into a connected web again, and pulling out the exotic Dutchman’s pipe wherever it drew eggs to their death. That patient, unglamorous work, carried on for two decades through schools, parks and bush-regeneration groups, ranks among the most heartening grassroots efforts on the coast.

And the birdwing repays the effort of reading the country rather than the creature. A strong flier, quick to find new vines, it comes back largely on its own once the food is rebuilt and the trap removed. Put the vine back across enough of the country and the butterfly follows.

Break the one link a specialist depends on and the specialist falls, however magnificent. Mend that link, patiently, garden by garden and gully by gully, and it climbs back. Not always. But sometimes.