Stuff.co.nz has an interesting article (and video) about 2011 kakapo chick "Solstice One" who has been suffering with poor health.

the chick might be suffering from "fatty liver", which can happen when rangers supplement the adult kakapo population's food sources. "It can be deadly – there was a chick a few years ago that died from it."

Kakapo have a 100 per cent herbivorous diet and rely on rimu fruit for much of their nutrition. In years when rimu trees fail to bear enough fruit, rangers give the birds pellets, but these can be too rich in protein and energy for the baby birds to tolerate.