A remnant population of the Floreana mockingbird on Champion island, Galapagos

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 Florea na became extinct approximately 125 years ago. We studied the Champion popu lation 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 censu sing of the whole population. The number of breeding adults varied from 16 to 24 with a mean of similar to 20. Using a standard population genetics fo rmula we calculate that the Champion population has lost half of the origin al level of selectively neutral heterozygosity since presumed immigration f rom Floreana ceased more than a century ago. The short-term future of the C hampion population is likely to be secure providing that goals and rats are not introduced, as these have caused much devastation on Floreana and prob ably resulted in the extinction of the mockingbird population there. (C) 20 00 Elsevier Science Ltd. All rights reserved.