Four tagged monarch butterflies out of 15,000 have flitted back to the suburbs they were bred in this spring, hopefully providing some insight into their winter behaviour in New Zealand, says the Monarch Butterfly Trust.
Small white labels were added to the hindwings of more than 15,000 monarchs during autumn by the trust's "citizen scientists", many of whom are children.
Four trust members, from Pakuranga, Hamilton, Tauranga and Nelson were "thrilled" to hear from neighbours that their monarch had been seen egg-laying in a nearby garden, said trust secretary Jacqui Knight today.
The orange and black butterfly is known for its spectacular migration. American monarchs can fly up to 3000km south to Mexico from as far north as Canada to wait out the winter in protected reserves. The survivors return north to start a new generation.
Ms Knight said before the trust started tracking monarchs, little research was being done to learn why they were retreating from urban New Zealand areas.
"Butterflies are pollinators - we need to know why they are becoming less common before they disappear altogether," she said.
Already there are major concerns for New Zealand's endemic forest ringlet, and the beautiful red admiral.
"I haven't seen any bees so far in my garden this spring. If the bees are retreating we're going to be even more dependent on our butterflies and moths for pollination."
Last summer during a visit, New Zealander Barrie Frost, from Queen's University in Canada, spoke highly of the efforts of New Zealand's "citizen scientists" who have been contributing to the study.
"The tagging programme is fantastic and beginning to yield very useful data. We hope that in future years we can find out if the butterflies return to the very same trees they roost in."
Butterflies were uniquely placed to act as indicators of environmental change, and "by tagging and following monarchs, we can use them as indicators of the status of our environment," Dr Frost said.
Ms Knight said several large clusters of monarch butterflies had been sighted in tree-tops around the country so far, mostly in parks where people walk and notice the movements among the branches on sunny days.
She urged people to look up while outdoors to spot tagged monarchs, and then lodge the information on their website.