Eggs of a non-chocolate variety are the focus of Kiwi Encounter incubation facility in Rotorua, after a clutch from Hawke's Bay came late and were smaller than usual.
The change was noticed in eggs sent from Forest Lifeforce Restoration Trust's inland Hawke's Bay Maungataniwha Kiwi Project in February and March, with similar results throughout the North Island.
Kiwi Encounter husbandry manager Claire Travers said the birds may not have been in peak condition, making them less keen to lay or sit.
"This could be a result of the very dry summer last year, which meant fewer invertebrates were available for them to eat."
While some eggs had decreased in size, Trust forest manager Pete Shaw said they had also produced the biggest on record.
"Despite the changes the Kiwi Encounter team is noticing, primarily in the second clutch, the first clutch of eggs from Maungataniwha this season resulted in the largest chick yet recorded at Kiwi Encounter."
The bird was named Fat Freddie after New Zealand band Fat Freddie's Drop and weighed 432g - nearly 100g more than an average kiwi chick at hatch.
This season, the inland Hawke's Bay Trust sent 43 eggs to Kiwi Encounter, 30 of which were viable; there are still a couple of Kiwi sitting on their nests.
After the incubation period, 27 chicks were sent to the predator-proof area at Cape Kidnappers where they will remain until they large enough to defend themselves in the wild - when they would be returned to Maungataniwha, or another partner conservation project.
The birds weren't related and their sires' territories did not share any similarities, however, new research was being done to determine whether habitat factors influenced offspring size or nest success.