It measures 40–50 cm (16–20 in) long with a 107–127 cm (42–50 in) wingspan.[5] This species ranges from 212 to 447 g (7.5 to 15.8 oz), with males averaging about 349 g (12.3 oz), as compared to the smaller female's 254 g (9.0 oz).[6] The basal half of the bill is red, the rest mainly black, and the lower mandible is much-elongated. The eye has a dark brown iris and catlike vertical pupil, unique for a bird.