less dramatically (but very noisily), my chicken-keeping neighbors abruptly had a rooster one morning. Who crowed all day, every day. That's when I learned some hens can spontaneously change into roosters.
Sex-reversal in birds (genetically male/female but appear female/male) is surprisingly common. Best detail: A genetically male bird called a laughing kookaburra had recently laid an egg. (1/2)
‘Sex reversal’ is surprisingly common in birds, new study suggests
Survey of five Australian avians finds numerous discordant individuals, including a genetically male bird that had laid an egg