Why Did The Passenger Pigeon Go Extinct? @Grrlscientist explains:

As extinctions go, the extinction of the passenger pigeon is truly a stupendous human achievement, unparalleled in recorded history: thanks to our penchant for relentless killing combined with large-scale habitat destruction, these iconic birds’ population crashed from billions to zero in just fifty years. But how could these birds decline so rapidly? Surely, people did not murder every last one of them, did they? Shouldn’t mind-bogglingly huge and wide-spread populations protect a species from extinction? Why didn’t some pigeons survive in remote areas?

It’s a fascinating story about genetic diversity, behavioral adaptivity, and more. But in the end, as the article says, the extinction of the bird was “entirely our fault.”