Feral Cat (Felis catus)

Feral Cats (Felis catus) are the single deadliest predator on birds, killing an estimated 1.3 to 4 billion annually in the United States alone—that’s faster than the average extinction driver. They have contributed to at least 63 species extinctions worldwide, more than Water Hyacinth (#9) has caused, though cat culling programmes face fierce public opposition. With a 30% higher kill rate than the runner-up among mammalian invaders, feral cats remain a uniquely controversial invader due to their domestic origin.