Also looks like heat lamp is held up by only the clamp. That's an almost guarantee of a fire - if you MUST use a heat lamp, chain it up - that clamp won't hold it. One bump from a chicken (and yes, very close to the roost) and it falls and up goes your coop.
I'm in upstate NY and have both pullets and adult birds outside with no heat. Been as low as -25 here (not this year, this year I think we hit +10 so far) and haven't lost a bird yet. if your birds are adults and have been outside with no heat, they'll be fine. Heat lamps tend to go boom and...