Juan de la Cruz (1542-1591)

Las condiciones del pájaro solitario son cinco.
La primera, que se va lo más alto;
la segunda, que no sufre compañía, aunque sea de su naturaleza;
la tercera, que pone el pico al aire;
la cuarta, que no tiene determinado color;
la quinta, que canta suavemente.

The conditions of a solitary bird are five:
First, that it flies to the highest point.
Second, that it does not seek after company, not even its own kind.
Third, that it aims its beak to the wind.
Fourth, that it has no definite color.
Fifth, that it sings very sweetly.