How old are they? What breed?
Chickens are not very "brave", anything flying over heard freaks them out, it's instinctive (flying predator). If they're cooped, they should be safe & sleep. Mine are housed at night, free range during the day although spend a good time in my patio lounging...
I know what you mean. I raise my chicks with the light on all the time until they're about 6 - 8 wks, the first time I turn the light off they freak out. So now what I do is turn the light off when the sun's still out, letting sunlight dim as the sun goes down. The gradual lights out is...