"Ríu Ríu Chíu" is known from the 1556 songbook called what?

“Ríu Ríu Chíu” is known from the 1556 songbook Cancionero de Upsala. The collection was printed in Venice by Girolamo Scotto under a much longer Spanish title and contains Renaissance villancicos for two to five voices.

The song appears as the collection’s fortieth piece among its Christmas villancicos. The book is also called Cancionero del Duque de Calabria or Cancionero de Venecia, so those names can cause confusion, but Cancionero de Upsala is the standard answer expected in this question.

Only one copy of the 1556 edition is known to survive. It was rediscovered in 1906 in the library of Uppsala University by Spanish diplomat and music scholar Rafael Mitjana, which explains the songbook’s familiar name and the spelling “Upsala.”

The carol’s authorship is less certain than its source: it is often attributed to Mateo Flecha the Elder, who died in 1553, but the piece is also described as anonymous. The repeated “ríu ríu chíu” may imitate a bird call, perhaps a nightingale or kingfisher.