The black-shouldered kite hunts by quartering grasslands for small creatures. This can be from a perch, but more often by hovering in mid-air. It is diurnal, preferring to hunt during the day, particularly in the early morning and mid to late afternoon. When a mouse or other prey is spotted, the kite drops silently onto it, feet-first with wings raised high. Prey is seized in the talons, it can either be eaten in flight or carried back to a perch. Birds will have a favoured feeding perch, beneath which accumulate piles of pellets or castings.
Black-shouldered kites take suitably-sized prey, including grasshoppers, rats, small reptiles, birds, and even (very rarely) rabbits, but mice and other mouse-sized mammals account for over 90% of its diet.