Though many invasive aliens are notorious for the harm they bring (pythons in Florida, cane toads in Australia, browntreesnakes in Guam), many others enhance the local nature scene.
The U.S. Fish and Wildlife Service says browntreesnakes have wiped out most of Guam's native populations of forest birds since being accidentally introduced to the island after World War II, probably after they stowed away on a ship or plane from their native range in Australia, Papua New Guinea and the Solomon Islands.