Sorry, milum, I am unable to help. To the best of my knowledge, NZ's bats ( both species, the only native non-aquatic mammals up here) all live in the South Island, and I haven't been up there in years.

Well, I used to live up there, and I've seen bats coming and going. Never seen them swarming or circling, though.

Is this a bit like water going down the plug hole?

- Pfranz