All over the world, pathogens and parasites introduced from other places represent a major threat to biodiversity. Small indigenous populations, such as Darwin’s finches on the Galapagos Islands, are particularly jeopardized. The Galapagos Islands are one of the few tropical archipelagos with a largely intact birdlife and, thus, an ideal workplace for the evolutionary biologist Sabine Tebbich: with the support of the FWF, she has been conducting field research there for more than 20 years, following the development of the Darwin’s finch population.