Weighting in at just 173.5 grams, the smallest kiwi chick to hatch at Rotorua's Rainbow Springs Kiwi Encounter has emerged from its egg.

The chick weighs just half the size of its 369 grams sibling when it hatched yesterday.

The 173.5 gram kiwi chick.

Kiwi Encounter husbandry manager Claire Travers says the arrival is very exciting.

Kiwi Encounter has hatched more than 1300 North Island brown kiwi eggs through the years and this latest arrival is the smallest the team has ever nurtured, and is also believed to be the smallest of its species in New Zealand.

'The little chick hatched all on its own and there was a team of very excited staff yesterday morning, one staff member even turned up straight out of bed on her day off, she was so keen for a look.”

The 'tiny' egg weighed just 217.6grams on its arrival from the Southern Whirinaki Forest and is a single anomaly from this clutch, which has produced one other normal sized egg that hatched last week.

By comparison, the sibling egg weighed in at 442.1 grams, more than double the weight of 'mini', and weighed 369 grams at hatch.

Previously the smallest chick to date was McMurdo - his egg was 292 grams at the same age and he weighed 238.5 grams at hatch.

All going to plan this chick will be released to establish a founding population of kiwi at the Otanewainuku Kiwi Trust near Tauranga.