The main predators of the mangrove finch are cats, fire ants, paper wasps, and especially destructive black rats and parasitic flies. The black rats (Rattus rattus) are predators that account for 54% mortality rate of the mangrove finch during egg incubation, while the larvae of the avian vampire fly (Philornis downsi) add an additional 14% mortality rate of newly hatched chicks.
The mangrove finch is vulnerable to attacks from cats, fire ants, paper wasps, and especially the destructive black rats and parasitic flies. The black rats are a major factor in the high mortality rate during egg incubation, while the larvae of the avian vampire fly also pose a threat to newly hatched chicks.