63. African Black-headed Oriole Another mainly yellow bird with a black head: why are so many birds coloured yellow? I don’t know. It’s not much good for camouflage, but if it’s a bright colour you want, yellow is a good one to go for. Perhaps arranging pigments just right to get that colour is less ‘expensive’ in evolutionary terms than other colours. Who knows? I managed to find a picture of Black-headed Oriole eggs: a very pale bluish white with dark spots. Why are eggs always egg-shaped, with a point at one end and rounded at the other? Actually, they’re not all like that. Some eggs, especially those of birds that nest in holes in trees or the ground, or in very deep enclosed nests, tend to be more evenly spherical. This is a clue. An egg laid there is very unlikely to roll out of the nest. But for those laid on the flat ground, as some are, or in rather shallow and open nests, there is such a danger. An egg of the traditional egg-shape, however, will roll not away but in a circle and return to where it came from (you can try this with a chicken egg). These birds; they think of everything. Birds of AFRICAMA House 130 Birds of AFRICAMA House 131