Crowned hawk-eagles have been known to prey successfully on large primates such as adolescent mandrills and young bonobos, and one primate probably looks just like another from an eagle's perspective. When scientists saw a dramatic crowned hawk-eagle attack on a sub adult mandrill, they were amazed that the eagle had the baboon on the ground, holding onto its prey with its talons, and striking repeated blows at the mandrill's head with its beak. A long tail is a crucial trait; the ratio of tail length to wingspan can predict the maneuverability of eagles. The hunting technique of small rain-forest hawks combines an interesting mix of active and inactive behaviours: they sit motionless and inconspicuous, but intersperse the inactivity with occasional swift and soundless flights from tree to tree. Nocturnal raptors usually hunt from perches and at fairly close quarters, without the impressive variety of adaptations found in diurnal raptors.