Martha (right), an extinct passenger pigeon, at the Smithsonian's Natural history Museum in Washington. The passenger pigeon was once the world's most plentiful bird. Sept. 1 is the centenary of the bird's extinction. Susan Walsh/AP hide caption itoggle caption Susan Walsh/AP The Two-Way The Flight Of The Passenger Pigeon, Now 100 Years Extinct September 1, 2014 Passenger pigeons were once the world's most abundant bird, but they were also the cheapest protein available. The last passenger pigeon, Martha, died exactly a century ago at the Cincinnati Zoo.