Join Gio Fitzpatrick and Neil Blake of the Port Phillip EcoCentre and learn why Gio has been building nest boxes for various birds and animals. Help build and install nest boxes for microbats. Microbats are small mammals about the size of a mouse. They are found throughout Melbourne, but you don’t often see them. Microbats eat about half their body weight in insects every night so they are great mozzie catchers.