A remnant population of the Floreana mockingbird onChampion island, Galápagos

Champion and Gardner are the only two satellite islands of Floreana in the Galapagos archipelago that support populations of the Floreana mockingbird, Nesomimus trifasciatus. The population on the much larger island of Floreana became extinct approximately 125 years ago. We studied the Champion population in every year from 1980 to 1991. Since the island is small (9.4 ha) we determined the demographic stability of the population by repeated censusing of the whole population. The number of breeding adults varied from 16 to 24 with a mean of ∼20. Using a standard population genetics formula we calculate that the Champion population has lost half of the original level of selectively neutral heterozygosity since presumed immigration from Floreana ceased more than a century ago. The short-term future of the Champion population is likely to be secure providing that goats and rats are not introduced, as these have caused much devastation on Floreana and probably resulted in the extinction of the mockingbird population there.