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8 May 2008

Darwin's Finches

Rob Morrison: Australia is known for its unique, even bizarre animals. But far away in the Galapagos Islands is a collection of animals that's equally unusual. Sonia Kleindorfer is an Australian researcher who knows them all well. Sonia studies evolution, not just in Australia but also halfway across the world in the Galapagos, helping to save some of the world's most famous animal species from extinction. So what takes an Australian scientist so far away from home?

Dr Sonia Kleindorfer: Australia is really a very big island. It has a number of islands off of its mainland, and islands are fantastic places to watch evolution happen. I'm very interested in the process of evolution, and so I compare my work in Australia with the work I do on the Galapagos, because the two systems inform my thinking. The Galapagos Islands are a group of volcanic islands off of the coast of South America. They've never been connected to the mainland, which makes them very special. There are about 50 islands. They vary in size. And islands are fantastic places to observe evolution happen because they are geographically separate and each island and each area is somewhat different. And so the animals become adapted to those particular conditions, like the tortoises.

You have tortoises with very round shells and high shells or flatter shells. And they can be found on either high or low islands. The boobies - some boobies have blue feet and others have red feet. The iguanas - on some islands they are very dark and on others they look like Christmas trees. But Darwin's finches take pride of place.

These little birds are related, but differ in their beaks and behaviour depending on where they are found. They helped Charles Darwin develop his theories of evolution. And since then, scientists all over the world have studied them to understand how species evolve.

The Charles Darwin Station is a big research station on the islands. They work closely with the Galapagos National Parks to manage the wildlife. And I work closely with both organisations so that our hands-on science can inform conservation management. I work on Darwin's finches.

There are 13 species of Darwin's finches and my group studies about four different species that are part of what we call the 'tree finch group'. We have several research projects that are all tied together by the underlying threat of introduced organisms to the Galapagos.

One is understanding the impact of an introduced fly that is threatening Darwin's finches. The fly will lay its eggs and larvae into the nostrils of the finch on the day that it hatched, maybe one to two days after it hatched. And it spends one life stage inside the nostril of the bird and then drops to the base of the nest where it will continue to suck the blood for the remainder of the nestling period. About 20% to 80% of the birds die.

Our research is aimed at understanding the biology of the fly - but also how we can control its spread, because it's considered the biggest risk to the survival of Darwin's finches now. During the breeding season, we go out and we look for nests. The finch nests are very conspicuous. They're very large and bulky. So they're easy to spot. We've developed a technique to spray the nests with pyrethrin, which is a plant-based insecticide. We know that the pyrethrin kills the larvae but it doesn't harm the finch nestlings. Those are important measures in the short term, but long-term conservation of Darwin's finches will need more.

We need to understand the genetic structure of the population because we want to introduce sterile insects that will mate with the females but not produce offspring. It's called the 'sterilised insect technique'. That's another good link with Australia, because Australia has developed the sterilised insect technique to fight the fruit fly problem.

If this infestation goes unchecked, Darwin's finches are at serious risk of extinction. We have already documented one local extinction of the warbler finch on Floreana Island. It is suspected that other finch populations are at extremely high risk now. But there are two islands that don't have the fly. And these islands have very restricted tourist numbers and access. This suggests that controlling human movement on the islands is very important to control the spread of disease and introduced organisms.

Visiting the Galapagos is transformational to anybody who goes there. And yet the very act of visiting it is actually changing it and may ultimately lead to the extinction of what we treasure on those islands. If we were to lose Darwin's finches, we would lose a window of opportunity to understand how life evolves on the planet. They are the best example to look at this question in the wild.