You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
Kereru Discovery and Great Kereru Count co-ordinator Tony Stoddard said the New Zealand wood pigeons spent much of the winter in remote bush, but returned to urban areas in spring to feed on nitrogen-rich foods such as willow, and to breed.
Because Dunedin had had such a mild winter and start to spring, they have been back in the city for the past couple of weeks.
"They're already being spotted in Dunedin and nesting. It's really unusual because it's quite early."
Mr Stoddard was delighted with the early return and hoped it signalled the local population was continuing to increase.
Today marks the start of the annual Great Kereru Count, which continues until September 29.
"Following the count in Dunedin last year, we noticed the numbers had really increased - it's a really healthy population in Dunedin."
He said it was because of pest control projects in the Town Belt and the abundance of food sources around the city.
This year would be a particularly important one for counting kereru, he believed.
"Rats and stoat numbers are increasing to plague proportions in some places, which is devastating for kereru.
"Kereru are one of our few native species that lay just a single egg, which sits precariously on an open nest platform.
"While a fully grown adult kereru has the wing power to protect itself from predators, eggs and chicks are very vulnerable.
He said kereru played a crucial role in dispersing seeds of large native trees such as tawa, taraire and miro.
They were the only bird left in New Zealand that could distribute these large seeds over vast distances and help keep native forests growing.
Dunedin residents can record the number of kereru they see each day by downloading the Great Kereru Count app.