The World No 3 initially looked firmly in control, but a blunder in the second-set tiebreaker helped hand the momentum to defending champion Novak Djokovic, who never gave it back.
US Open champion Murray, a set up and 2-2 in the tie-breaker, halted in the middle of a second serve to catch a white feather as it floated to the ground.
It broke his concentration and he double-faulted, helping Djokovic win the set. The Serb then reeled off the third and fourth sets for victory as Murray was increasingly hampered by foot blisters and a tight hamstring.
Afterwards, Murray conceded that stopping for the feather, from one of dozens of white seagulls flying around Rod Laver Arena, may have been a mistake.
“I mean, I could have served. It just caught my eye before I served. I thought it was a good idea to move it,” Murray said.
“Maybe it wasn’t because I obviously double-faulted. No, you know, at this level it can come down to just a few points here or there.”
Murray, 25, said his best chance for victory came at the start of the second set, when he let Djokovic off the hook by blowing three break points.