Wellington City Council is urging dog owners to keep their pets under control while at the beach, after two little blue penguins were killed over the weekend.
The penguins were killed in an off-leash area at Houghton Bay beach.
Another blue penguin was killed by a dog on Wellington's waterfront last month.
City councillor Peter Gilberd said the deaths were "a stark reminder" that dogs must be monitored by their owners, and kept on the leash where required.
"It is frustrating that the message isn't getting through that people must maintain control over their dogs at all times, whether they're on a leash or not."
He said in this case the dog owner had acted responsibly by alerting the authorities.
"I don't think people have any ill will," he said.
"I think it's unfortunate, but it does show we need to learn from it."
He said it was important to stay vigilant, especially around the rocky areas built up to stop erosion where penguins were likely to be nesting.
"We don't see them, but the dogs smell them out, no trouble at all," he said.
Urban Ecology team leader Myfanwy Emeny said they had a lot of information on the movements of little penguins in the Wellington Harbour area because the birds had been tagged.
"We know that during the months of May and June, adult birds come ashore to prepare nests which can be up to 1.5 kilometres inland," she said.
Emeny said little blue penguins were vulnerable to dog attacks throughout the year.
Little blue penguins are protected under the Wildlife Act. The Department of Conservation has the power to prosecute in cases where the dog owner is at fault.