The Brown Falcon is a small to medium-sized raptor (bird of prey). Birds range in size from 41 to 50 cm, with the female larger than the male. The Brown Falcon has a range of plumage colours, from very dark brown to light brown above and off-white below. Generally, the upperparts are dark brown and the underparts are pale buff or cream. The sides of the head are brown with a characteristic tear-stripe below the eye. Birds from the tropical north are very dark, with a paler face and undertail, while those from central Australia are paler all over.
Brown Falcons breed at most times of the year, but more commonly in June to November in the south and November to April in the north. The nest used by the Brown Falcon is normally an old nest from another hawk species, but the species may build its own stick nest in a tree. Occasionally birds nest in open tree hollows. Both sexes share the incubation of the two to six (normally three), eggs, and both care for the young, although the female performs the bulk of these duties, while the male supplies most of the food. The eggs hatch after about 30 days, and the young birds leave the nest after another 40 to 45 days.
The Brown Falcon ranges throughout Australia, and north to New Guinea. It is found in all but the densest forests and is locally common throughout its range. The preferred habitat is open grassland and agricultural areas, with scattered trees or structures such as telegraph poles which it uses for perching. Around outback towns, the birds become quite tame and will allow quite close approach. Birds may stay within the same areas throughout the year or may move around locally in response to changes in conditions. Paler birds are normally associated with inland areas, but all the colour varieties are fairly scattered throughout the range. The Brown Falcon is normally silent at rest, but gives some cackling and screeching notes when in flight. Brown Falcons are normally seen alone, searching for food from an exposed perch. When prey is sighted, the bird swoops down and grasps it in its claws (talons). Less often the species will hunt by hovering or gliding over the ground, often at great heights.
Brown Falcons feed on small mammals, insects, reptiles and, less often, small birds.