Nutrition aids breeding attractiveness
A study by the Zoological Society of London (ZSL) has revealed that the reproductivity of rare hihi birds is improved with a diet of carotenoids.
Carotenoids – the natural pigments found mostly in fruit and vegetables – enable males to develop more bright and colourful feathers, allowing them to outshine their rivals when breeding later in life.
Over the course of a year, scientists looked at the effects nutrition has on the New Zealand hihi, also known as stichbirds, after they are born. The birds were found to develop more attractive breeding features when they grew up on a diet high in carotenoids.
"We first hand-fed baby hihi birds either a carotenoid supplement – natural pigments used to colour yellow, orange and red – or a more complete dietary supplement," explained Leila Walkers, a ZSL and University of Cambridge PhD student who took part in the study.
"Then we looked at the effect this had on male breeding feather colour once those chicks had grown and moulted into their adult plumage."
The importance of a bright and colourful plumage is paramount in many bird species, including the hihi, as it demonstrates strong health to females. Due to their attractiveness, they are then more likely to be chosen for breeding.
Dr John Ewen, a ZSL research fellow, commented: "We saw that nestlings receiving more carotenoids were brighter as adults. This was a combined result of the carotenoid-rich dietary supplement they received, and the carotenoids they obtained as part of a natural diet fed to them by their parents."
The study has highlighted how sensitive birds are to experiences early in life and is part of a wider conservation effort to help rebuild the New Zealand coloured bird population. Almost all species of hihi requires food supplementation support in the wild.
Next, the scientists are hoping to further test the effects of mating success and to narrow down a diet that helps in producing hihi bird offspring.
The results have been published in the journal Proceedings of The Royal Society B.
The BSAVA has opened submissions for the BSAVA Clinical Research Abstracts 2026.
