In classical Greek mythology, Halcyone, daughter of Aeolus, was married to Ceyx, King of Thessaly. On a voyage at sea, Ceyx fell overboard and drowned. Halcyone turned into a kingfisher when she saw his corpse. Her lamentations awakened the gods who then turned Ceyx into a kingfisher, and Ceyx and Halcyone mated. Their nest of bones and shells floated on the open sea as Halcyone brooded over her young. Aeolus, her father and the god of wind, quieted the sea for seven days on either side of the winter solstice to protect this union. Milton immortalised these “Halcyon” days in the Hymn of the Nativity when he wrote “While birds of calm sit brooding on the charmed wave.”

In reality, only one species of kingfisher is pelagic and none nests on the sea, but they have evolved other interesting traits, most notably ocular adaptations that are deserving of recognition.

Evolution has found specialised adaptations to fit specialised niches. Coloured oil droplets, located in the inner segments of cones, can be found in lungfish, diurnal reptiles, turtles, and birds. Amphibians, snakes, crocodiles, and placental …