"I was up late one night watching TV alone in the living room when I was about 12. Heard my dog growling in the kitchen. Sometimes he does that when he sees something in the backyard - a cat, a squirrel, a plastic bag blowing in the wind, the moon, whatever.
So I went to investigate and saw 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 crept over and looked outside. I saw nothing. After watching for a minute or two, I figured it was probably a raccoon that's left by this point, so I opened the door to let the dog out.
He stepped 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 looked off towards the shed, scanned around it, and nothing. Then my eyes drifted upwards, toward the tree hanging over the shed. There was some dark, undefined shape up in the tree, and the instant my eyes fixed on it, it quickly 'floated' up like a wisp of smoke being blown away, and disappeared 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 started barking at it. He was still right in front of the door, so I reached forward and grab his collar, yanking him inside and booked it the heck out of the kitchen. I tried 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."