Alkonost

The Alkonost is the bird of paradise in Slavic mythology. It has the body of a bird with the face of a woman. The name Alkonost came from the name of Greek demi-goddess Alcyone transformed by gods into a kingfisher. The Alkonost reproduces by laying eggs on the sea-shore then putting them into the water. The sea is then calm for six or seven days at which point the eggs hatch, bringing a storm. For the Russian Orthodox Church Alkonost personifies God's will. She lives in paradise but goes into our world to deliver a message. Her voice is so sweet that anybody hearing it can forget everything. Unlike Sirin, another similar creature, she is not evil.
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[Other] In Russian legends Alkonost is "the bird of paradise", a miraculous bird with a human face. Alkonost lays eggs on the sea-shore, then puts them into the water, becalming the sea for six or seven days; and on the sixth or seventh day Alkonost's nestlings hatch and a storm begins. Alkonost has a very loud voice; those who hear it will forget all they know and wish. For Orthodox Church Alkonost personify God's Will.