After planning to let nature take its course, wildlife officials moved a stranded Emperor penguin from a New Zealand beach to a zoo Friday after its health appeared to be worsening.

The young penguin had been eating sand and small sticks of driftwood, which it tried to regurgitate. First seen on a North Island beach Monday, the penguin appeared more lethargic as the week progressed, and officials feared it would die if they didn't intervene.

The rare venture north by an Antarctic species captured public imagination, and experts initially said the bird appeared healthy and well-fed and intervention was unnecessary. They became concerned enough to step in Friday.

Three experts lifted the penguin from the beach into a tub of ice and then onto the back of a truck. The bird was docile enough they didn't sedate it for the 65-kilometre journey from Peka Peka Beach to the Wellington Zoo, said one of the participants, Colin Miskelly, a curator at Te Papa, the Museum of New Zealand.

It made sense that a penguin might mistake sand for Antarctic snow, which Emperors eat for hydration, Miskelly said, but he had no explanation for the bird eating wood.

Miskelly said experts at the zoo were considering sedating the penguin and putting it on an intravenous drip as they tried to nurse it back to health. Ideally, the bird would heal enough that it could be released into the wild.

Miskelly noted no facilities in New Zealand were designed to house an Emperor penguin long-term. It's the tallest and largest penguin species and can grow up to 122 centimetres high and weigh more than 34 kilograms.

Christine Wilton, the local resident who discovered the penguin Monday while walking her dog, was back at the beach Friday to say goodbye.

"I'm so pleased it's going to be looked after," she said. "He needed to get off the beach. He did stand up this morning, but you could tell that he wasn't happy."

Zoo spokeswoman Kate Baker said veterinarians would give the bird a full health check. The zoo clinic has a salt water pool which has been used in the past to nurse smaller varieties of penguins, she said.

Often sick birds require rehabilitation for a month or two before being released, Baker said, adding that some creatures with severe injuries remain in captivity.

Experts believe the penguin is about 10 months old. It stands about 80 centimetres high. Experts haven't yet determined whether it is male or female.

Emperor penguins typically spend their entire lives in Antarctica, the coast of which is about 3,200 kilometres from the North Island beach where the penguin was stranded. It has been 44 years since an Emperor penguin was last spotted in New Zealand.