I just got chickens in my current playthough, and I started them in my under-Elder base. I created a room for them directly under the alter fire and sealed it up to the roof (floor of the alter).

Just after the eggs hatched, I got a bat raid. I had saved up all game for those eggs, and had about 200 coin to spare. I was so afraid that the bats would find some way to get in, but I ran out to lead the bats outside, dealt with them, and ran back in to check my chicks. They were fine!

Yeah that's a good idea, you could even use burial mounds in BF or even crypts in swamp if so inclined

Some troll caves are better than others. as hey have between 0 and 3 chests,based on my experience. Burial chambers can have more chests (up to five?) but they are not at the same place.

I mean, indoor locations also make good treasure rooms.