Im not sure why everyone is blaming this on the motion light.
My rooster starts talking very early in the morning. Like around 4 or 5. We don't have a motion light. However we DO have a set of neighbors that get up for the day around that time and another one coming home from work before dawn. They're turning on lights, letting pets out etc.
My chickens are very far away from the house but can apparently still hear us. The rooster starts talking about the neighbors before dawn and then everyone starts demanding breakfast and to be let out when they hear us get up. Thankfully we live in the country and no one cares.
So. Um, maybe it's NOT the motion light?
If you live close enough that the neighbors hear your chickens the chickens are probably reacting to something going on in the neighborhood every morning. Maybe someone is up getting ready for work? Turning their house lights on and moving around? Someone suggested covering the windows at night to block out light. That might help. Also maybe if you put a dish of scratch in their coop when they go to bed they'll just wake up and eat that? It's worth a try.
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I am thinking the same thing. Car headlights, someone turning on a porch light while their dogs to out etc.
I know my motion light triggers to leaves and branches blowing around.
Yes the birds could be reacting to the sudden loss of light as it goes off too.