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BiologyThis hawk is an active and versatile predator, feeding on invertebrates, small lizards, snakes, rodents, hatchling tortoises and sea turtles as well as the marine iguanas found on the Galapagos Islands. It also takes carrion and is often associated with human camps, where it takes food scraps (5). There are no natural predators of this species on the Galapagos, and they show very little fear of humans (3). Breeding may occur at any time of year (2). This species tends to form long-term groups consisting of one female and several males. The female mates with all of the males, and they all assist in chick rearing. This type of social structure is known as 'co-operative polyandry', polyandry meaning 'many males' (6). Nests are constructed in low branches, on an outcrop of larva or on the ground from sticks, and are lined with grass, bark, leaves and other available soft materials. They are used repeatedly for several years and become increasingly large, often up to 1.2 metres in diameter and three metres in height (3) (5). During courtship, pairs often rise to great heights and descend in criss-crossing flights (5). Mating occurs repeatedly during the day. Although up to two greenish-white eggs are laid, just one chick is usually reared (5). The incubation period lasts 37 to 38 days and the young are fully fledged at 50 to 60 days of age (3).