Animal play is notoriously difficult to describe, particularly in birds (Ficken 1977). Play is most common in the young of a species (Loizos 1966), a life stage when conflicting environmental pressures are reduced by parental care. In 11 of the 13 orders of birds for which play has been reported, the young are altricial (Ortega and Beckoff 1987). Beckoff and Byers (1981) classified avian play into three categories: locomotor play (primarily play in flight), object play, and social play. Play with objects, reported for eight avian orders (Ortega and Beckoff 1987), is widespread in wild populations of birds of prey (see Ficken 1977) and may involve manipulating prey animals or inanimate objects such as twigs or stones. During play, an object is often carried into the air, dropped, and then caught with the feet, with the act repeated many times (Ficken 1977). We report here on object play by the Northern Harrier (Circus hudsonius). Ours is not the first report of play in the Northern Harrier (Sumner 1931), nor of harriers playing with inanimate objects (Bildstein and
Hamerstrom 1980, Bildstein 1992). We describe repeated acts that constitute the first report of play by a Northern Harrier with an unknown inanimate object, and speculate on why this activity may lend fitness to an individual harrier.