When And Why Do Birds Molt? What Is Molting?

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A molting cardinal.

Do you know much or anything about why or how birds molt?  When birds molt they can completely change their appearance with new colors for various reasons.

Many animals, including insects, reptiles, and birds molt.  It is obvious when a snake molts because it crawls out of its old skin.  For birds, molting may not always be as obvious of that, but it is just as important.  Here is all you need to know about what is molting in birds, and why and when they do it.

What is Molting?

As I talked about in an earlier post about what molting is and what animals do it – molting is the process of shedding the feathers, skin, or similar and replacing them with new growth.

For snakes, molting means that they lost their old skin.  The literally, crawl out of their old skin and have new skin.  For many insects, molting means crawling out of their exoskeleton and growing a new one.

What is Molting For Birds?

Molting in birds is not the same as for insects or snakes, like crawling out of their old skin or exoskeleton.  Rather, molting is when birds replace some or all of their feathers with new ones.

Complete molt – when a bird loses all of its old feathers and replaces them with new ones.

Partial molt – when a bird only loses some of its old feathers and replaces them with new ones.  For example, a bird may molt its flight feathers.

Why Do Birds Molt?

It is important because it keeps birds feathers in a good, healthy condition which is crucial for their flying.  Some of the other reasons that birds molt is that molting provides the bird with a new look or color.  After they molt their new colors will serve as a sign of the bird age, sex, or the time of year.

When Do Birds Molt?

It takes birds a lot of energy to molt and grow new feathers.  Due to this birds try to molt at times of year when there are not other activities occurring that need a lot of energy, such as building nests or migrating.  The two most common times of year for birds to molt is either before or after the breeding season.

birds molt

Another bird that is molting (A greenfinch).  Photo via Flickr.

How Often Do Birds Molt?

Most birds molt according to one of the following three main patterns:

One complete molt per year – many birds only have one complete molt per year.  There are many kinds of these birds, including chickadees, flycatchers, hawks, hummingbirds, swallows, and woodpeckers.

One complete molt and one partial molt per year – many other birds will molt all of their feathers after nesting.  Then before the next breeding season, they will have a partial molt.  At this time the males will grow bright colors in order to attract a mate.  Birds with this approach to molting include buntings, tanagers, and warblers.

Two complete molts per year – The final approach, which only a few  birds choose, it to make two complete molts every year.  These birds tend to live in areas that put a lot of damage on their feathers and so they need to be fully replaced.  Some of these birds include Marsh Wrens.