Mr Hamer said 649 of the 1018 were aged between 0-9, suggesting parents were speaking te reo to their children. However, he warned gains would be affected by intermarriage, residential and occupational dispersal and a lack of official support.
"Given the influence of the many factors that promote language shift away from te reo Maori, this increase is unfortunately unlikely to be sustainable," Mr Hamer said.
Glenis Philip-Barbara, chief executive of Te Taura Whiri i te Reo Maori, the Maori Language Commission, said she took a more optimistic view.
"I think it's a good thing when more Maori speak Maori. I think that that's positive. When you're living in a community that's not your own of course you're going to want to strengthen that connect to home."
Asked if she was concerned about the impact of Maori migration on the language domestically, she said while it could depopulate language communities, one of the "silver linings" might be that people who become passionate about the language overseas might return "with an increased desire to roll their sleeves up and participate in this collective project of ours to regenerate the language - hei reo korero [to speak Maori]."
Lessons a long way from Otara
Sheryl Wiki says complacency stopped her from learning Maori when she lived in New Zealand.
Ten years ago the former Work and Income New Zealand worker, now 40, moved to Sydney from Otara. Soon after she discovered that a school - Te Reo Maioha - was offering Te Ataarangi courses for beginners.
While she'd taken classes 18 years ago, she hadn't kept them up. Ms Wiki said she was happily surprised to find an offering in Australia.
"It boosted my urge to do it. How often were you going to go overseas and find anything Maori?"
She is still involved at the school, supporting teachers and has a fluent father who also lives in Australia.
"It's about holding on to our identity, holding on to who we are. We were created as a unique people in the world and our reo is part of that. We [Australian Maori) probably put more effort into it because it's harder for us to get it."