Thick-billed raven, Simien Mountains, Ethiopia (© Ignacio Yufera/FLPA/Minden Pictures)

Perched high in the mountains of Ethiopia, Eritrea and Somalia, the thick-billed raven holds the title of the world's largest raven. At more than 70 centimetres in length and weighing around 1.5 kilograms, it is about a quarter heavier than the common raven. Its enormous, arched bill—pale at the base and close to 9 centimetres long—is the largest among perching birds. These ravens live mostly between 1,500 and 3,400 metres above sea level, found across farmland, rocky cliffs and even rooftops in mountain towns.