www.fundaciomiro-bcn.org:
The moon and the sun, the female principle and the male principle, night and day, forces that simultaneously oppose and complement, are constant references in Miró's work. Like the Sun Bird, the Moon Bird is also a severe form with a polished surface, and its overall appearance evokes certain primitive or votive figures.
The Sun Bird looks more like a bird, while the Moon Bird is closer to Miró's personages that belong to the terrestrial world. The former is more horizontal, more static, the latter more vertical and dynamic.