Who will shell out for my pre-17th century fossilised bird egg? Christie's Travel, Science and Natural History specialist James Hyslop examines a pre-17th century fossilised bird egg on display at Christies" auctioneers in London. The egg, which is 100 times the size of an average chicken egg, measures 21cm in diameter and 30cm in height. It would have been laid by an elephant bird, pictured, an extinct species from Madagascar. The egg is up for auction in the Travel, Science and Natural History sale on 13 April.