Our supplementary feeding programme has proved to be an effective way of ensuring that kākāpō are healthy enough to breed and increasing the number of eggs laid; we’ve found that females lay larger clutches when provided with a nutritional supplementary food.
On the other hand, if mothers are given too much supplementary food they tend to produce more sons than daughters, which is not desirable because our goal is to achieve more breeding females.
By carefully monitoring the weights of individual females and adjusting the amount of supplementary food provided accordingly, we’ve found that we can equalize the number of male and female chicks produced.
Breeding in kākāpō is triggered by unusually abundant rimu fruit crops that occur, on average, only every three years. More often than not the rimu crop fails to ripen, which necessitates hand-rearing most, or all, chicks to prevent their starvation. Hand-rearing is not only expensive and labour intensive, hand-reared chicks grow more slowly than those raised by their mothers (when sufficient rimu fruit is available).
Therefore, we ultimately would like to develop a supplementary food that not only increases clutch size but also allows females to successfully raise their chicks when the rimu fruit crop fails to ripen.
Current research, in collaboration with Yvette Cottam (Massey University), Prof. David Raubenheimer (Massey University) and Prof. Kirk Klasing (University of California), is focusing on developing a supplementary food that mimics the nutritional composition of ripe rimu fruit.