In 1969, Michael and Kathy Willis said they bought a piece of land covered in gorse and broom on the outskirts of Christchurch.
There was no roading or urban development nearby, but their dream was to one day open a zoo.
"I had looked forward to that moment since I was young, so when it finally came to fruition it was quite surreal," Michael said.
"It was quite scary at the time, people called me a crazy dreamer."
"When mum and dad opened Willowbank, they didn't even have an entrance building, they just sat in an old Land Rover with a shoe box as a till and put an ad in The Press advertising 25 cents an adult and 10 cents a child," said son Mark Willis, who is now co-director with his sister Kirsty.
Willowbank was the first to open a glass-free nocturnal house for kiwi in a natural environment and has worked with many conservation projects.
The milestone birthday has had Mark and sister Kirsty reflecting on their far-from-ordinary childhood living at a wildlife reserve.
"We named him Lewis and he did everything with us. Mark would take him for walks on a lead and down for a swim, and he even used to sleep in my bed.
"Then he grew bigger teeth and bigger claws so playing started becoming a bit painful after a while."
"We genuinely feel that we've only got this far because of the support from the community so now we want to give something back," Mark said.
"Right from the very beginning we've had help from other people, people who brought into our dream, and for that we'll be forever grateful," Kathy said.
