The Ascension frigatebird is a large lightly built seabird with brownish-black plumage and a deeply forked tail. It has a wingspan of around . The male has a striking red gular sac which he inflates to attract a mate. The female is slightly larger than the male and has a brown breast-band and sometimes a white belly. They feed on fish taken in flight from the ocean's surface (mostly flying fish), and sometimes indulge in kleptoparasitism, harassing other birds to force them to regurgitate their food.