The term "passenger pigeon" refers to a species of bird that was once abundant in North America, but is now extinct. The passenger pigeon was known for its large flocks and migratory behavior, traveling hundreds of miles each year in search of food. They were also important to Native American tribes as a source of food and their feathers were used for various purposes such as insulation or stuffing pillows. However, due to overhunting and habitat destruction, the passenger pigeon became extinct with the death of its last known individual in 1914.