Extinction: The Story of the Passenger Pigeon
- Brief history of the events leading up to the extinction.
- http://www.eco-action.org/dt/pigeon.html

Passenger Pigeons
- Describes their breeding, and how they were hunted to extinction.
- http://www.amnh.org/exhibitions/expeditions/treasure_fossil/Treasures/Passenger_Pigeons/pigeons.html

The Passenger Pigeon
- Contemporary descriptions of flocks of living birds from prominent naturalists.
- http://www.ecotopia.org/about/pigeon.html

Encyclopedia Smithsonian: Passenger Pigeon
- Summary of the biology and extinction of the species, including a description of their exhibit of Martha, the stuffed remains of the last living specimen of the species.
- http://www.si.edu/resource/faq/nmnh/passpig.htm

Passenger Pigeon
- A drawing of what the birds looked like, and brief background information.
- http://www.songbird.org/birds/extinct/passpigeon.htm

Wikipedia: Passenger Pigeon
- Encyclopedia article that talks about the life and eventual extinction of this bird.
- http://en.wikipedia.org/wiki/Passenger_Pigeon