Grallistrix can be loosely translated as "owl on stilts". The genus received this name due to the long legs and presumably terrestrial habits which they evolved in the absence of mammalian predators on their island homes. They fed on smaller birds such as Hawaiian honeycreepers. While they were well able to fly, they may have stalked sleeping birds on foot, or raided seabird colonies at night.
When the islands were settled by humans since the late 1st millennium AD, the owls presumably rapidly succumbed to the depredations of introduced pigs and possibly Polynesian Rats, as well as habitat clearance for agriculture. They were never seen alive by scientists, being known only from plenty of subfossil bones.