Passenger Pigeon
North America
Extinct in 1914

Main causes: Hunting & Habitat loss

They were the humans of birds in terms of socialness. They flew together in such tremendous groups that they would literally block out the sun. Because of their colonial nature for migration and breeding, they were extremely easy for humans to hunt in mass numbers, and it's also why the last captive handful could not be successfully bred. The last passenger pigeon - Martha - did not lay a single fertile egg with any of the other few captives at the Cincinnati Zoo. The new Americans dropped their numbers from a couple billion to zero

The giant flocks of passenger pigeons contributed to the disturbance and regeneration cycles of the hardwood forests they used, like fires and destructive weather. These cycles are like a reset button for these habitats, forcing their affected areas to regrow engineered with increased biodiversity