How a bird which often hangs around the coast knows when conditions are good inland is difficult to guess, but those ones knew something was going on. Vast flocks numbering in their thousands will, when the conditions are right, accumulate for nesting and breeding — sort of a pelican fertility festival.
Each pair will look after a couple of eggs and share the job of feeding and raising the chicks. The young don't have feathers when they hatch and so they are vulnerable to the bright sun. If you see a mature pair of pelicans, the big one will most likely be the male, and if they are nesting it's a good idea not to approach the nest. Many species of birds, including pelicans, will sometimes abandon their chicks permanently if they see people getting too close to it. That's why I only photograph nesting birds from a distance.
References
Reader's Digest Complete Book of Australian Birds
Reader's Digest Services Pty Ltd, 1979
Simpson & Day, 1993, Field Guide to the Birds of Australia
Viking O'Neil, Penguin Books Australia Ltd |

Immature Australian pelicans have brown feathers where the mature ones have black. And no, its head has not been put on backwards |