"Ahu" are stone platforms on which many moai sit. There are 313 known ahu and 125 of these carry moai. The biggest, Ahu Tongariki is 220 m (720 ft), and had the most (15) and tallest moai.
The male Mallard has a glossy green head, grey wings and belly, while the female has a brown-speckled plumage. Mallard ducks have a moulting season, they are vulnerable during this time as the moulting stops them flying.