As a specialist predator of passerines, particularly honeyeaters, but also feeding on insects, the square tailed kite takes the majority of its prey from the outer foliage of tree canopies (3). This species is a known nest robber, snatching eggs and nestlings directly from the nests of smaller bird species, occasionally even taking the entire nest (8). The square-tailed kite may also feed on reptiles and small mammals (4). Hunting regularly, twice a day in the morning and afternoon or evening, this species covers large distances (3), searching for its prey from the air. The square-tailed kite is an agile species that, despite its long wings, is well adapted to hunting in woodland, gliding slowly either above or just below the canopy (7).
Square-tailed kites form monogamous pairs, reportedly for life (3). However, this species is more often solitary outside of the breeding season (7). Female square-tailed kites lay eggs from July until December, and breeding pairs nest solitarily. Nests are constructed 8 to 34 metres above the ground, usually in the fork of a living woodland or forest tree. The nest itself is generally 50 to 85 centimetres across, 25 to 60 centimetres deep and lined with green leaves (8). Clutch size of the square-tailed kite is between one and three eggs which are incubated by both sexes for around 37 to 42 days, and the minimum nestling period is nine weeks after hatching. However, fledglings may beg for food from adult birds for more than a month after leaving the nest (3).
The square-tailed kite is a highly mobile species, and populations in the south migrate to the tropics during the winter months (4).