Sách nói: Passenger Pigeon

"For the last three years I have spent most of my leisure time in collecting as much material as possible which might help to throw light on the oft-repeated query, 'What has become of the wild pigeons?' ... I am merely a business man who is interested in the Passenger Pigeon because he loves the outdoors and its wild things, and sincerely regrets the cruel extinction of one of the most interesting natural phenomena of his own country. ... It is hard for us of an older generation to realize that as recently as 1880 the Passenger Pigeon was thronging in countless millions through large areas of the Middle West. ... They were slain by the millions during the middle of the last century, and from one region in Michigan in one year three million Passenger Pigeons were killed for market. ... The American people are wasteful. They are just beginning to learn the need of economy in the use of that which Nature has flung at their feet." (from the Introduction to The Passenger Pigeon by William B. Mershon, 1907)
On September 1, 1914, just seven years after Mershon's book was published, the last known passenger pigeon died at the Cincinnati Zoo.