So weird I should have read about something like this but by covering their wattles, you may confuse your girls on who is exactly who. I'll let you decide if it has any merit but the blog post cites a prior study.
http://scratchandpeck.blogspot.com/2010/05/same-only-different.html
excerpt from the post:
"
In Sy Montgomery's new book, Birdology,
she talks about a study that was conducted to see how chickens tell each other apart.
Scientists took a flock of chickens of a single breed and painted their feathers different colors, and the chickens still recognized their friends and flockmates.
But then they put little hats over their combs, and the chickens couldn't figure out who was who.
"
Might be fun to do anyway, lol.
http://scratchandpeck.blogspot.com/2010/05/same-only-different.html
excerpt from the post:
"
In Sy Montgomery's new book, Birdology,
she talks about a study that was conducted to see how chickens tell each other apart.
Scientists took a flock of chickens of a single breed and painted their feathers different colors, and the chickens still recognized their friends and flockmates.
But then they put little hats over their combs, and the chickens couldn't figure out who was who.
"
Might be fun to do anyway, lol.