Jeremy,
Leon is talking about the huge Flying Fox bats we have! Their wingspan can reach 1.5m! And when they crap, you REALLY don't want to be under it!
I get flocks of hundreds fly over my house every night, dozens of which raid the giant Morton Bay Fig trees across the road from my place
I used to have a big mandarin tree in my backyard. One night I stepped out into the backyard for a stretch when one of these HUGE bats lept out of the mandi tree with its huge wings going "WOOP, WOOP, WOOP!!!" Heck, my backbone jellified instantly!!!
PS, added a photo of a lady holding a flying fox to give you an idea of just how big these beasties can get! A bit bigger than the little tacker you found, I'm sure