On rare occasion, I have had a bird squeak at five and six months old.
I recall last year at the combines shipping night, for an old bird race. I heard one squeaking in the trailer and wondered if someone accidently (or intentionally) put a young bird in the basket. But it would have had to have an old bird band. Which is possible.
We do not take trainers during old bird season, so it wasn't that situation.
I never was able to locate the bird by visual inspection through the openings in the trailer. Just heard it squeak now and then. I felt sorry for it because it sure sounded like a young bird.
