The expression "rare as a hen's tooth" comes from the fact that chicks in the egg have what is known as an "egg tooth" on their beak which helps them break out of the shell. They lose it almost immediately after hatching. Hence the expression.
It’s almost exclusively the males, or toms, and they’ll gobble to attract a hen. But hens make noise too, just usually not gobbles. They can yelp, cackle, and whistle.
The expression "rare as a hen's tooth" comes from the fact that chicks in the egg have what is known as an "egg tooth" on their beak which helps them break out of the shell. They lose it almost immediately after hatching. Hence the expression.