"I think it's a good reminder that people need to keep their dogs secure. Who knows where they will end up and what damage they could cause," Ms Wiles said.
In each fairy tern - or tara-iti - breeding season, DoC employs rangers to monitor the nests, provide public education and work with the public.
"With less than 40 fairy terns left, we ask residents to be vigilant about their dogs," communications ranger Abigail Monteith said.
A Whangarei District Council spokeswoman said the incident is a reminder to dog owners to keep their dogs out of reserves, make sure they are under control at all times and registered.
"As a working dog this one would not usually have had to be microchipped [working dogs are exempt].
"However, all dogs that have been impounded must be microchipped before leaving the pound, even if they are working dogs.''
The owner was fined for not registering their dog then had to pay a late registration fee to bring the dog's registration up to date.
Consequences such as a hefty fine would hopefully act as a deterrent to other dog owners, DoC said.
There are only four known fairy tern breeding sites - at Waipu, Mangawhai and Pakiri, while the other is Papakanui on the Kaipara Harbour's south head.
In the breeding season, the birds lay eggs in exposed scrapes in sand just above the high tide mark.
The scrapes are often destroyed by high seas, sand drift, predators, pets and, unwittingly, people.
While the population of about 44 birds seems fairly stable, if still very low, the fairy tern was on the brink of extinction in 1983 when there were only three known breeding pairs.
