I have three straight run 15 week old RIR chickens? When a neighbor sexed them for me at 10 weeks I was told they were hens. About three weeks ago they all started crowing at sun up and at various times throughout the day. I live within city limits so Roosters are not allowed. I have looked at every picture I can find of RIR and mine look like hens, but sound like roosters.

There are no physical distinctions other than slight comb variations (just enough to tell them apart) So is it possible I have three roosters and no hens? Do hens crow when they are not laying?(I have heard and wad that they sometimes crow when they have laid but mine are not old enough to lay yet.)

Thanks in advance for any and all info.