What is happening!? Cockerels everywhere?

[Crazy for Chickens!]

I had a chicken 4-her tell me of a way to sex chickens: hold them upside down by their feet (gently!). If they try to right themselves immediately, they are female. Males just stay inverted.

It worked for me, but.......I don't raise enough birds to really check it out. Has anyone else heard of this or is it an old farmer's tale?

This is just an old wives tale.