Two penguins were killed by a dog in Wellington at the weekend, just two weeks after another of the birds was killed.
The latest attack was at Houghton Bay beach in an off-leash exercise area.
Wellington City Council is frustrated by the death, a spokesperson saying owners needs to supervise their dogs - even in off-leash areas.
It follows the killing of a little blue penguin by a dog which wasn't on a leash along the Wellington waterfront on June 26.
It only takes a number of seconds for a dog to kill a little blue, the world's smallest penguin species.
City Councillor Peter Gilberd, who holds the city's natural environment portfolio, says both attacks are a "stark reminder of the need to keep all dogs on a leash where required, and strictly monitored when not".
"It is frustrating that the message isn't getting through that people must maintain control over their dogs at all times - whether the dogs are on a leash or not."
Little blue penguins are protected by the Wildlife Act, which is administered by the Department of Conservation (DoC).
Mr Gilberd says DoC has the option to prosecute owners.
According to the council, during the months of May and June adult penguins come ashore to prepare nests which can be up to 1.5km inland.
Little blues are found all around the Wellington coastland, and they're vulnerable to dogs throughout the year.
Their populations are declining in areas where they're not protected from predators.