A bird once numbering in the billions was gone within a few decades

Passenger pigeons were likely the most numerous bird in North America, with single flocks reported to darken the sky for hours and estimated in the billions. Commercial hunting and habitat loss drove the population to collapse so fast that the last known individual, a captive named Martha, died in the Cincinnati Zoo in 1914 -- one of the fastest total extinctions of an abundant species ever recorded.

— Smithsonian National Museum of Natural History, Passenger Pigeon — extinction confirmed 1914