Ghosts in the attic

When we first started cleaning out the attic in anticipation of sistering the joists, we found a bunch of hay and chicken wire stuffed into the eaves. We just figured the hay was being used as old-school insulation, and the chicken wire was simply keeping it in place. Now that we have some floor decking down, and I can easily reach the eaves without risking death by falling, I began a more thorough cleaning of the area via ShopVac. The first time one of these:

It's a bat, in case my photography skills don't do the discovery justice.

got stuck on the end of the hose, I was startled. But I hit the hose on a piece of wood and down the bat carcass fell. I resumed my work, picking up at least 4 more bats and 1 small bird. Bats and little birds happen in attics sometimes, especially in really old houses. Keep in mind that I was alone in the semi-dark, working by the light of a single bulb.

Then this happened:

Oh, yes. That's a chicken. Or, it *was* a chicken at some point in the past 140 years. Notice how I didn't even bother to take the ShopVac hose away. I switched off the vacuum, got my camera, and called it a night. Here's a glimpse into my thought process:

1. Ack! A chicken!
2. Why is there a chicken in my attic?
3. How did a chicken get up here?
4. I'm pretty sure it didn't fly up here.
5. I don't know of any chicken-sized holes in the house it could've walked through.
6. Somebody put the chicken up here on purpose?
7. Well, that explains the hay.
8. I've never heard of people keeping chickens in their attic.
9. Why is there a chicken in my attic?
10. Fresh eggs?
11. There aren't any stairs or steps leading up to the attic, so getting eggs would be a huge hassle (especially with a 10' ceiling height upstairs).
12. WHY is there a CHICKEN in my ATTIC?
13. Forget it. I'm going home.
14. Really, though. Why is there a chicken in my attic?

Any ideas?