Wow, 2 million is a lot of bats...and bat shit! No wonder the smell was so bad. I like the sound of 'cauldron of bats' too, it just sounds more fitting. I really love the shot of the bat looking straight at the camera (8ith pic up, I think), though all of the shots are great. I have a few bats that live on my property and they fly out at dusk every night. It's nice to have them here, eating up those skeeters :D
It's likely a combination of poop and other secretions as well.
Cauldron of bats sound indeed fitting and unique. There are a lot of groups of animals called colonies already 🤨
Nice! They know they’re safe in your area that’s why they live there. So cool! I also just learned that they eat insects like mosquitoes as well so that is sooo cool!!