It's a real whodunit, a murder mystery that has the experts stumped.

The discovery of a dead kiwi on a busy Whangarei street has experts baffled.

There is one known kiwi population near the city in the Pukenui Forest, where 12 kiwi were released with transmitters and microchipped on March 17.

However, none of those birds are missing, although one strolled into the lounge of a Ngahere Drive home in Maunu on Easter Monday.

The discovery has led to reminders for people to watch out for the endangered birds on the district's roads.

The juvenile kiwi was found on Kamo Rd, between Wrack St and Kensington Ave, on Wednesday evening.

The person who found it thought it was injured, but when Robert Webb, from the Whangarei Bird Recovery Centre, arrived, it was dead.

Webb says the kiwi had died recently and been hit by a vehicle.

Webb took the bird to the Department of Conservation who confirmed the dead bird did not have any microchip or transmitter.

Pukenui Forest Trust ranger Bevan Cramp said the bird was not one of those released into the forest.

''We monitor ours daily to keep a track on them and make sure they don't go too close to urban areas. If they do, we pick them up and put them back into the forest.''

Cramp said with more efforts to protect the national bird, seeing kiwi in urban areas would become more common and people should take care on the roads at night.

Ngaire Tyson, co-ordinator with Kiwi Coast in Northland, said where the dead bird came from was a total mystery because there were no kiwi populations around the central city any closer than the Pukenui Forest birds.

Tyson said the death of any kiwi was sad and it appeared this one was almost certainly a wild bird because those released into the wild would have a microchip and/or transmitter attached.

''At this stage we don't know for sure if the bird was hit and killed on Kamo Rd, or killed elsewhere and then left on the road there.

''I don't think kiwi should be hanging around on Kamo Rd in Kensington. There are populations at Mt Tiger and the Whangarei Heads area is a kiwi stronghold, but none that close to the city.''

Tyson said the death was a warning for people to take care driving at night, even if they are in an urban area.

''Over coming years kiwi will be come in closer and closer to the city fringes and urban areas. That's going to become really common and people shouldn't wait until there's a kiwi death in their neighbourhood before they take steps to help, like tying their dogs up at night.

''Also put any possum traps at least 750mm above the ground. You don't want to learn there are kiwi in your garden by finding one dead in the possum trap you have laid on the ground.''