Rotamah Island had previously been a farming property, and the observatory was established in 'Overstrand', the homestead built in 1908.
In 1985 the observatory was visited by Prince Charles and Diana, Princess of Wales.
These factors give visitors easy access to both freshwater and marine habitats.
There is a small population of the introduced Hog Deer on the island.
In 2001 negotiations between Birds Australia and Parks Victoria, on renewal of the lease to the observatory, broke down and Birds Australia's association with Rotamah Island ended.