Bairstow, a veteran of the 2013-14 tour when England were whitewashed 5-0, said he would welcome the return of suspended all-rounder Ben Stokes but was confident the squad would do England proud at the Gabba regardless.
"Content, relaxed, excited," the 28-year-old told reporters at Brisbane airport when asked to sum up the mood in the camp.
"We're ready to go, we're excited about the prospect of the first test.
"We know that we've worked hard leading up to this test match but it's about how we front up on the first morning of the first test at the Gabba when everyone's watching.
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"(But) if you can't get up for an Ashes series, if you can't get up for England against Australia, what can you get up for?"
Vice captain Stokes has been suspended since being arrested on suspicion of causing actual bodily harm outside a Bristol nightclub in September.
A report in Britain's Daily Telegraph on Saturday said that police would make a decision over whether to charge Stokes this week, potentially leaving him clear to join the England squad before the second test in Adelaide.
"It would be amazing if Stokesy comes out here, he's a fantastic cricketer," said Bairstow.
"We don't know what's going on there, it's completely out of our hands. We're hoping it's resolved sooner rather than later because at the end of the day we want the best cricketers playing in the Ashes.
"That's the series that we want."
The first test starts at the Gabba on Thursday.
(Reporting by Nick Mulvenney; Editing by Amlan Chakraborty)
