What is molting, the process of birds changing their feathers?

Have you ever seen bird feathers lying around in your daily life?

Every year around July or August, you can often see feathers lying on the ground in Copper Pheasant enclosure and the Japanese bird enclosure at Inokashira Park Zoo.

It could be a feather that has fallen out due to the bird flapping its wings, but it could also be a sign that the bird is undergoing molting, a process of replacing its feathers.

A tail feather of a male White-rumped Pheasant was found lying in the exhibit area.

Many birds replace their old feathers with new ones around summertime, after breeding and raising their young. Like our hair and nails, feathers cannot be repaired once damaged. Feathers have various roles, such as allowing birds to fly, maintain body temperature, and protect them from rain and wind, but they gradually deteriorate and lose their function through daily life. Therefore, it is necessary for birds to replace their feathers with new ones regularly.

Since losing all their feathers at once would make them unable to fly, most birds, with the exception of a few species, regrow their feathers gradually. During molting, the arrangement of feathers is disordered because the new feathers haven't fully grown in yet, making it difficult to fly properly. Also, molting requires a lot of energy, so during this time, birds remain still and quiet.

During the molting season in July and August, when we clean the exhibit area, we find various feathers falling every day. By looking at the shape and size of the fallen feathers, we can tell which parts of the bird's feathers are being replaced, such as "flight feathers" (the feathers on the wings used for flight) and "tail feathers" (the long feathers around the tail).

Also, when the birds start shedding their feathers, it signals that the breeding season is over and molting season has begun. For animal keeper, molting is one of the signs that indicates the changing of the seasons.

A male White-rumped Pheasant during molting (photographed July 6, 2026)

A male White-rumped Pheasant during molting (photographed July 21, 2026)

If you come across any feathers lying around the exhibit, be sure to take a closer look at the birds. Observing them while imagining which parts of their feathers are being replaced, or whether they are quietly spending their molting period, might give you a different perspective on the birds than usual.

[Inokashira Park Zoo]

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