Бернардино де Саагун
In the 16th century, Friar Bernardino de Sahagún had reported that a red bird matching the description of the red warbler was regarded as inedible by the Aztecs. Researchers Patricia Escalante and John W. Daly isolated two alkaloids in preliminary investigations of the feathers. The presence of these alkaloids render the bird unpalatable; humans find it inedible.