Ceyx was shipwrecked and died the tragic death that his wife feared. The gods appeared to Alcyone in a dream in the image of the drowned Ceyx, and told her of his death. Alcyone ran to the seashore and found Ceyx's body drifting slowly towards her. Stricken with grief , Alcyone jumped into the sea to meet his body, but the gods took pity on her and before she could be overcome by the waves she was transformed into a kingfisher. Ceyx was changed into a bird as well, but their love was unchanged. They are always seen together, flying or riding the waves.
Zeus forbade the winds to blow for seven days prior to and seven days after the winter solstice and every year at this time the sea lies still and calm; no breath of wind stirs the waters… for this is when the kingfishers brood over their nests floating on the sea. After the young birds are hatched the charm is broken, but each winter these days of perfect peace come, and they are named after Alcyone, or, more commonly, "Halcyone days."
Adapted from "Mythology" by Edith Hamilton, 1942