"We are carefully managing (the) supply of eggs due to the current industry challenges," McDonald's Australia said in a message to customers this week.
As a result, breakfast orders will stop at 10:30 a.m. instead of midday, it said.
"We are working hard with our suppliers to return this back to normal as soon as possible," it said.
Australian authorities say H7 avian influenza has emerged at nearly a dozen poultry farms across Victoria, New South Wales and the Australian Capital Territory.
The government said chickens at the infected farms have been "depopulated" -- a euphemism for extermination.
Scientists say the bird flu strain is genetically related to viruses detected in Australia's wild bird population and is not the H5 strain spreading elsewhere in the world.