The shape of birds' eggs varies considerably, for reasons that are unclear.
The peculiarly elongated and pointed shape of the Common Guillemot's egg is thought to prevent it from rolling off the narrow cliff ledge it is laid on, but new research suggests instead that the shape has more to do with providing resistance against impacts and protection from faecal and other contamination.
"I have studied guillemots for over forty years and have never been convinced by the rolling explanation. It has been exciting coming up with new ideas and testing them," said Dr. Tim Birkhead, lead author of the Ibis study.
Explore further: Unique shell design gives guillemot eggs an edge for living on the edge
Ibis, DOI: 10.1111/ibi.12458