Skerns are flightless seabirds that have evolved a unique behavioral quirk in response to the problem of incubating eggs in this hostile environment. As well as being a hazardous time for the embryo chicks the parent birds also run the risk of exposure. The skern has solved the problem by laying its eggs in the warm volcanic sands of the islands and deserting them immediately afterwards. It is able to delay the time of laying until the temperature of the sand is exactly right. When a volcano shows signs of activity it immediately becomes the scene of frenzied activity. The birds scramble ashore, and with the aid of their temperature-sensitive beaks probe the sand for areas with the right condition for incubation. After laying their eggs 10-20 centimeters deep and covering them with sand they return to the sea, seeing neither their eggs nor their offspring again.