Perception was easily accomplished, required little effort, and it never had to stand the test of reality.
Many people believe everything others say, even though what they see with their own eyes, should be enough to tell them otherwise.
No amount of telling is worth doing it once.
But this was no ordinary chicken. This chicken was evil manifest.
Wizards First Rule: People are Stupid
Everybody knows it. Wizards are supposed to have beards. It's common knowledge.