From NPR Science Friday -- Ten miles off the west coast of Scotland, the Firth of Clyde flows around a small island shaped like a sugar loaf called Ailsa Craig. In breadth, it’s shy of a mile but rises steeply to more than 1,100 feet, carpeted with grass and heather. An abandoned watchtower recalls a time when people once lived on the island, though today it’s completely uninhabited. Devoid of rats but full of rabbits, the outcrop is also a bird sanctuary where species such as gannets, guillemots, and puffins breed on rocky cliffs during the spring. The island is for sale.