I found this poem:
Yo soy la blanca paloma
que en el cardal de la loma
canta con tristes asentos,
penas que llevan los vientos;
yo soy la blanca paloma.
I realy want to listen the entire song in the cartoon!
The song comes from an opera: Calandria, Comedia de Costumbres Campestres, written by Martiniano Leguizamón (1858-1935). Actually, is present in Act VI, "El bailecito".
There is a short piece of sheet music in the opera script in the virtual Cervantes Library.