Moonlarks, or suldreen in the Enlightened Language, are rare birds. Moonlarks lay their eggs in the oceans and allow for the tide to carry the eggs away. Baby moonlarks must fend for themselves in the world without a family. A parent is, however, always secretly watching out for them to make sure they're safe. They sing melodies of guidance or comfort that help the baby moonlarks, as while they are physically alone they are never truly so. Because of this nesting habit, the Black Swan named Sophie, Project Moonlark. she was tossed out into the sea of humans, other than Mr. Forkle secretly watching her. Alden borrowed two moonlarks from the Sanctuary to study their habits in Book 1. They live in habitats with water; Alden used the lake at his home.
Moonlarks have silver feathers, long legs like a crane, a neck like a swan, and a long tail like peacocks. They are described to be quite beautiful.
Sophie was dubbed Project Moonlark by the Black Swan. When Sophie was a baby, her family said that she was trying to pronounce her name, but instead of saying Sophie, she said Soybean. That ended up being a nickname throughout when she was living with humans. It turns out she was saying "Suldreen" or Moonlark in the Enlightened Language, neither Sophie or soybean.