The dragon heads outside the caves are more than just scenery. Normally the formations have no eyes. But when a Dragon Egg spawns in a nest somewhere on the island, all of the dragon rock formations will have clear crystal eyes for that day.
Dragon Rock Statue on a day a Dragon Egg has spawned
The crystal eyes will remain all day long even after an egg has been collected, but only as long as the player remains on Kozita. After leaving to Florens and returning, the eyes will no longer be there unless there was another egg that was previously not found (it is possible for more than 1 to spawn in a single day).