Mr Leach, a visitor from Glasgow, Scotland, stopped at Arthur's Pass on Wednesday to take in the views at a rest area along State Highway 73.
He left the windows down as he snapped photos of the scenery, including one of an unusual bird on the ground near his vehicle. Little did he know he'd become a target for the local criminal element.
"A Canadian couple walked by and said: 'We've just seen that bird take something out of your campervan'," Mr Leach laughed.
"It took all the money I had. I was left with $40 in my pocket."
The unsuspecting tourist had stashed his travel cash - about $NZ1300 (about $A1100) - in a small cloth drawstring bag and left it on the dashboard, where the bird apparently found it while rummaging through other items.
The kea grabbed the bag and made a clean aerial getaway.
Fortunately, Mr Leach had old friends nearby, Paul and Lyn Fisher of Normanby, who lent him cash to tide him over.
Hoping to recover his money through travel insurance, Mr Leach sheepishly reported the incident to Timaru police.
"The man I dealt with was very serious for the first few questions," Mr Leach said.
"Then he said, 'Do you mind if I just stop to laugh?' "
Mr Leach said he had never heard of the mischievous kea before his visit.
"The birds are now lining their nests with £50 notes."
Keas are known for being highly intelligent and strong, but also highly mischievous, with a reputation for opening rubbish bins, damaging furniture and vandalising cars.