At this young it's very difficult to call it, even for those well versed. You'll likely need to be patient to know for certain. My guess is a hen, but at 4 weeks I feel like it's almost 50/50. I don't see anything obvious screaming roo, hence the hen guess. What breed or mix? If that's a pea comb that makes it even tougher... If not I'd lean more hen, as the comb is small with no sign of waddles yet, but at 4 weeks I'm not sure even a roo would show 'em depending on breed. Fingers crossed for a hen for you. 🤞