Sexing quails in winter

[Faraz1]

Hello, any ideas on how to sex my quails during winter. They are around 8 weeks now and I cannot see any foam forming on the vents.

any other ideas apart from isolating them one by one to see if they crow?

 

[Nabiki]

Give them extra light. They'll start to crow or lay if they're getting 14-16 hours of light/day.

 

[Faraz1]

Unfortunately giving them extra light is not an option. Any other ideas ?

 

[NY Coturnix]

post some pics and if they're feather sexible there are people on here that can identify.