Like most owls, the Spotted Owl is a nocturnal predator, and everything about its form is adapted to that purpose. It uses its long, sharp talons to dispatch and hold prey and a strong, hooked beak to tear the bodies of its prey into pieces it can swallow. Its plumage is cryptic, designed to blend into the shadows of the forest understory so the owl can sleep peacefully during the day, undetected by larger predators or smaller birds that would disturb its rest.

The Spotted Owl finds its prey primarily by hearing and has the ears for the job. Its big, round face is a complex assemblage of feathers that gathers sound like a parabolic microphone, funneling it into large ear openings on each side of the face. Owl ears are unlike any others in the bird world, and not just because of their size. Many species, the Spotted Owl included, have asymmetrical ears, that is the right ear is a different size and shape than the left. In some species, such as the Boreal Owl, this asymmetry is built right into the skull, whereas in the Spotted Owl and its relatives it is restricted to the fleshy part of the ear opening. But the function is the same-the asymmetrical shape of the ears allows the owls to pinpoint the location of any sound in three-dimensional space.

The large, dark eyes of the Spotted Owl are also key to its success as a night hunter. Owl eyes are supremely adapted for low light conditions, with round lenses set close to the retinas to maximize light gathering. Like cameras operating in low-light situations, the owls obtain this sensitivity at a cost-the resolution of their eyes is rather poor. That is, they can see large objects very well at light levels in which we would be bumping into telephone poles without seeing them, but they lack the detailed vision that allows hawks and eagles to spot mice at great distances. But then, Spotted Owls use their ears to spot the mice, and only need night vision to find branches to perch on and to avoid hitting tree trunks while in flight.

Some owls, such as the Barn Owl, find their prey by coursing back and forth over fields all night, but the Spotted Owl is a sit-and-wait predator. Its strategy is to perch silently in the forest and listen intently. If it hears the scratching of woodrat toenails on a log or the thwack of a flying squirrel landing on a tree trunk, it launches itself towards the sound, homing in on the prey with the accuracy of a laser-guided missile. Its flight is silent, quietened by the special structure of the leading flight feathers and the velvety texture of all the wing feathers. It needs this silent flight to fly to the prey undistracted by the sound of flapping wings.

The Spotted Owl has another interesting characteristic it shares with almost all other raptorial birds, something that has nothing to do with sharp talons and beaks. The female is considerably larger than the male; females weigh about 625 and males about 550 grams. The reason for this reversed sexual dimorphism, as it is called by biologists, has been the subject of great debate for decades. It is almost surely linked to the strong division of labour in hawks, eagles and owls. In these species, the female performs all the nest duties such as incubation of the eggs and brooding of the young, while the male does almost all the hunting for the family. Perhaps the small size of the male allows him to eat less of the prey he catches so that he can pass more on to the growing family, or maybe it makes him more agile so he can catch flying and jumping prey more easily. Or maybe the female needs to be larger to let her produce and easily incubate a large clutch of eggs. The theories are almost endless.

As in all species, the structure and behaviour of the Spotted Owl is the result of millennia of evolution and interaction with its environment. Being a predator near the top of the food chain, it is perhaps more sensitive to changes in that environment than other species.