At what age should brown kiwi (Apteryx mantelli) eggs be collected for artificial incubation

We recorded the fate of brown kiwi (Apteryx mantelli) eggs collected from Northland forests for artificial incubation at Auckland Zoo. The hatchability of eggs of different ages were combined with known rates of egg losses in the wild to derive models which predicted that optimal hatching success (>64%) was when the oldest egg in a brown kiwi nest was 41-57 days old at the time the eggs were collected. Collection before this interval risked egg failure resulting from unknown developmental problems associated with artificial incubation of freshly-laid eggs, whereas later collection of clutches risked failures in the wild before the eggs were collected. Robertson, H.A.; Colbourne, R.M.; Nelson, A.; Westbrooke, I.M. 2005. At what age should brown kiwi (Apteryx mantelli) eggs be collected for artificial incubation? Notornis 53(2): 231-234.