I was thinking something more like just a picture of their heads.
Doesn't work on turkeys unless you have sex linked poults. I have seen it claimed but not proven that Narragansett female poults are lighter colored than Narragansett male poults. One person made the claim that his Bourbon Red poults looked different and followed them into adulthood with a correct prediction of their sexes.
I personally have raised a fair number of Bourbon Red poults and never saw any color or pattern difference in the poults. Guaranteed it doesn't work on Slate poults or Royal palms.
After all they are turkeys.