Chickens won't leave coop

[LargeTalonChickens]

Hi everybody first time chicken owner and poster. I come to these helpful forums today because my chickens are exhibiting some odd behavior (odd even by chicken standards lol). I've raised six baby chicks that hatched in May so they are roughly 3 months old. They've been living outside since the beginning of June in their coop/pen and everything has been aces they go outside all day and go inside at night. However, today, August 2nd, I went out to check on them and they were oddly all inside their coop still and it was 10am, which is extremely odd for them. I went to the pen door and they all came bustling out as they normally do and they started to scratch around their run as if it was a normal day. Later I came out around 1pm and they were all back in the coop. I don't have food or water in there as the food and water is outside. The weather has been a mild 75 degrees today and if they were getting a little overheated they normally go under the coop in the shade. The only thing I can think of is that something rattled them in the middle of the night. My coop is right next to the woods. There wasn't any sign that a predator tried to break in. My coop is 4 ft off the ground and only accessible by a ramp. I do keep the coop door open because the ramp leads out to their pen which is surrounded by hardware cloth that goes 1 ft under ground on all sides, it also has hardware cloth as a roof so it is extremely hard for any kind of predator to get in. I also have a motion light that should startle any would be predators as well. Any thoughts on this strange behavior?

 

[oldhenlikesdogs]

Mine stay in when they see something that frightened them, could be something like a hawk, snake, or even a low flying plane can cause panic, especially in younger birds.