We found a possibly injured pigeon last night but today it's not moving

Hello. Last night we found a pigeon on our back porch, still alive walking around but unable to fly. We got some seed for it and went inside, it is currently December where I'm at. This morning when we checked on it, it was kinda stiff, but still standing it's head still up and it's eyes closed. We finally found a box for it and an old shirt to try to warm it up just in case it's still alive but we're not sure if it is or not.