How old are they? If they are under 2/3 months, it may be a little difficult for the untrained eye, but once they start interacting with each other as they mature you will see.
The males are usually more aggressive and defensive of their territory. They have deeper voices, are larger, have bigger crops and coo loudly and will proudly walk and display themselves with dances when they find or think they have foud a hen. With hens it can be a little more difficult as they are softer spoken and not as aggressive, they can be bullies too, when they are young, but you know you have a hen once they lay that first egg.
The males are usually more aggressive and defensive of their territory. They have deeper voices, are larger, have bigger crops and coo loudly and will proudly walk and display themselves with dances when they find or think they have foud a hen. With hens it can be a little more difficult as they are softer spoken and not as aggressive, they can be bullies too, when they are young, but you know you have a hen once they lay that first egg.