I visited The Pond at Elephant Head run by Bill Forbes.  Flash and camera triggers are set up on the flowers, which the bats eagerly feed upon.  At a small pond flash triggers are set up and the camera is set to take continuous shots until the battery runs out.  The trick to this photography is in the set up which Bill largely takes care of.  

The lighter colored bats, most of the ones drinking, are Pallid Bats, Antrozous pallidus.  The other are Mexican Long Nosed, Leptonycterus nivalis. 

The treat for this kind of photography is twofold:  enjoying a glass of wine watching the flashes trigger, and seeing what you got!

The pond is located in Amado, Arizona and a Google search will provide all the details if your interested in setting up a shoot.