"I was up late one night watching TV alone in the living room when I was about twelve. I heard my dog growling in the kitchen. Sometimes he does it when he sees something in the backyard - a cat, a squirrel, a plastic bag blowing in the wind, the moon, whatever.
So I go to investigate and see him standing at the door with the hair on his back standing way the heck up. Like the way I've only ever seen it when he's about to get into a fight. Or wants to. So I creep over and look out. I see nothing. After watching for a minute or two, I figure it was probably a raccoon that's left by this point, so I open the door to let the dog out.
He steps out a few feet and stops in front of me, looking off towards the shed in the back corner of the yard. It's the middle of the night, and only the back porch light is on, which isn't enough to really light up the whole yard. I look off towards the shed, scan around it, nothing. Then my eyes drift upwards, towards the tree that hangs over the shed. There's some dark, undefined shape up in the tree, and the instant my eyes fix on it, it quickly 'floats' up like a wisp of smoke being blown away, and disappears in the backdrop of the night sky. No sound whatsoever, no flapping of wings, not even the rustling of branches.
My dog goes freaking mental and starts barking at it. He's still right in front of the door, so I reach forward and grab his collar, yank him inside and book it the heck out of the kitchen. I try to wake my mom up, blabbering about some dark cloud in the tree, but she's fast asleep.
To this day, I have no idea what it could've been."