Why do birders create State lists?

["Wendy" <>]

Often bioregions here can be very large here too.
You could look at local government / city council areas if you want to use
smaller areas, these are entirely political not ecological boudaries,
generally, though.
There are also Country Fire Authority areas which for example divide
Victoria into 5-6 large areas, 20-30 smaller ones. I am unsure of the system
in the other states. I doubt any local birders use fire regions as list
areas and locating the boundaries may be tricky.

I wish you well for your trip Down Under

Wendy