Mimus trifasciatus survives in low numbers on Champion and Gardner-by-Floreana, 2 islets in the Galápagos.
- Black rats, Rattus rattus:
- probably caused the extinction on Floreana
- are present on islets near the 2 breeding islands and there is a risk of accidental introduction.
- Unusually dry La Niña years:
- correspond with higher adult mortality
- are increasing in frequency. This is thought to be driving the current decline.
- Diseases. Floreana mockingbirds are affected by:
- Philornis downsi, an invasive parasite
- avian pox virus. This is thought to be responsible for the increased mortality on Champion during the 1982-1983 El Niño event.
- The smooth-billed ani Crotophaga ani:
- is known to prey on other bird species on the archipelago
- has been seen on Champion
- Loss of genetic diversity:
- caused by the loss of immigration from the now extinct Floreana population.
- has raised concerns for the long-term survival of the 2 remaining populations.