Moulting: keeping up appearances

Over the next few months, you may see fewer manu/birds around or some looking a bit worse for wear. This is because many will be going through their post-breeding moult, which is when they shed and regrow new feathers in advance of winter. Feathers get worn out and damaged over time, and unlike hair, they do not continually grow even if they get damaged; they need to fall out or be removed in order to stimulate new feather growth. Damaged feathers can result in compromised ability to fly, thermoregulate, and mate.

Patterns and frequency of moult vary depending on species and age: some manu may have one or several moults throughout the year, and these may be partial or full body moults. Hihi juveniles, for example, undergo a partial moult after fledging; this is when males gain their breeding plumage.

They then undergo subsequent moults after each breeding season. Interestingly, there is evidence that hihi males will target specific foods during moult, in order to gain the carotenoid pigments responsible for their yellow plumage! On the other side of the spectrum, kiwi continually shed their loose, fur-like feathers throughout the year.

Manu will moult gradually and in a sequence across an area of their body to ensure there are no bald spots. However, it’s a taxing process, making manu more vulnerable to predation – which is why many of them lay low during this period. For example, pāteke males have two annual moults, one of which follows breeding and renders them flightless for a time. Hoiho/yellow-eyed penguins and other penguin species remain on shore for 3-4 weeks to undergo a full body moult; during this time, they will typically lose 3-4kg as they aren’t waterproof and therefore can’t go to sea to feed. Given their vulnerability during this period, it’s particularly important that we continue to look out for manu by trapping and keeping pets on leads or indoors.

Photo by Rory Wilsher