(CBS) — It was 100 years ago when the passenger pigeon became extinct. WBBM’s Steve Miller spoke with a Chicago author who chronicled the disappearance of the species.

“It’s rare when we know when the last of a species died,” said Joel Greenberg.

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Joel Greenberg is the author of “A Feathered River Across the Sky: The Passenger Pigeon’s Flight to Extinction.”

Don’t confuse them with the pigeons that we see every day in the city, those are different species.

"A Feathered River Across the Sky: The Passenger Pigeon's Flight to Extinction." by Joel Greenberg.

“A Feathered River Across the Sky: The Passenger Pigeon’s Flight to Extinction.” by Joel Greenberg.

Greenberg says the last passenger pigeon was named Martha, and she died in 1914 at the Cincinnati Zoo.

“Martha was almost certainly born in Chicago in the back yard of Prof. Charles Otis Whitman at the University of Chicago.”

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Martha spent her life in a cage, the last survivor of her kind.

“The passenger pigeon would darken the skies for hours at a time.”

That was in the early to mid 1800s and they were literally hunted into oblivion.

“They were the cheapest terrestrial protein available in North America. Game was unprotected.”

Greenberg says the demise of the passenger pigeon did bring about protections for wildlife.

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This week, a passenger pigeon specimen is being unveiled at the Peggy Notebaert Nature Museum.