A certain sign – apart from crowing – that a chick is male are shiny pointy saddle feathers. They can appear from 12 weeks of age onwards but in some breeds they may take up to 20 weeks to appear.
These pointy feathers become very obvious when using a piece of paper.
Pullets (see picture below) only have rounded feathers.
In henny feathered breeds like the Sebright the males don’t grow shiny pointy feathers.
The presence of these shiny pointy feathers is a sure sign it is a male but their absence doesn’t guarantee it’s a female.