Members of the public had reported seeing the birds on moving cars, and then trying to fly away.
"They are 1-year-old, teenagers, still having fun."
They also seemed to copy each other.
"[Car surfing's] a bit of a problem."
There was little DoC could do about it, other than educate people to not encourage the birds around people and their cars, Mr Stewart said.
The Kea Conservation Trust said some of the inexperienced birds were not gaining height as they attempted to fly off the moving vehicles.
It asked motorists to slow down until they were sure kea were not attached to the car roof.
- The Greymouth Star