The plumage of some birds changes noticeably during the course of the year, with bright feathers becoming temporarily drabber once the breeding season is over. By the following breeding season, the vibrant feathers are present once more, with no trace of the dull plumage they have replaced.
This process, known as molting, is an entirely natural part of a bird’s life cycle and is generally painless and harmless. But how and why do birds molt, and how often does it happen? Read on to learn more.
When birds molt, they shed their older, weaker and damaged feathers, and replace them with new, stronger ones, which help them fly more efficiently. Strong feathers are vital not only for flight, but play a major role in a bird’s ability to stay warm and dry in winter.
Molting cycles and frequency varies between different bird species, and may happen at various stages in a bird’s life. Not all birds undergo a radical molt with particularly noticeable changes to their plumage, but wear and tear of feathers is an issue that affects all avians, and worn out feathers do need to be replaced periodically.
Our guide to molting explains how it happens and why it is necessary. Keep reading to discover more about whether all birds molt and how long the process takes.
A Blue Jay going through a full molt
Molting is the process of replacing feathers, experienced by birds regularly during the course of their lives. The plumage of each bird species is adapted to its environmental conditions, and different birds will need to replace feathers for different reasons and at different points in their lives.
Adult birds do not keep the initial fluffy feathers they have as nestlings and fledglings forever. Even during the course of a year, an adult bird’s full set of feathers may be gradually replaced with one or more brand new full or partial sets each year. Types of molt include:
Male Common Blackbird going through a moulting cycle
When birds molt and new feathers develop, their post-molt appearance may not always be the same as immediately before they shed their previous plumage. Some bird species have what is known as an alternate, or breeding, plumage, which temporarily transforms their appearance each year. Others have the same coloration all year round, known as a basic plumage.
Close up of a male American Goldfinch molting into breeding plumage
Birds’ feathers are made from keratin, and when they become weak and worn – from flying, injury, or abrasion, for example – they cannot regenerate themselves. Weakened feathers make flight far less efficient and it becomes necessary for some, or all, of the damaged feathers to be replaced. This is a natural and unavoidable part of a bird’s annual life cycle.
The males of certain species molt ahead of the breeding season, acquiring a more vibrant set of feathers with the purpose of attracting a mate.
Once they have served their purpose, the colorful plumage is then shed, and replaced with a less conspicuous set of feathers, enabling the birds to enhance their chances of survival by blending into their surroundings.
A very ruffled molting male red-winged blackbird
How often a bird molts varies from species to species. Molts also occur as birds develop between fledging and juvenile stages to reach adulthood.
It takes a while for young birds to develop their adult plumage. For example, many smaller songbirds have shed their juvenile plumage and are indistinguishable from adult birds after around a year. Some seabirds may take significantly longer, with some gull species undergoing a series of molts before achieving their adult plumage after around four years.
Swallows, hummingbirds, and thrushes are among the species that undergo one full molt per year. During this time, they replace and renew all feathers with a fresh, healthy set.
Bird species that swap their distinctive plumage during the breeding season to a more drab appearance shortly afterwards complete one full molt cycle and one partial molt each year. These birds include American goldfinches, buntings, and warblers.
Even though females of these species do not have such a stark difference in plumage, they still undergo a partial molt ahead of the next breeding season.
Some species undergo two complete molts twice per year, particularly species that live and breed in areas where navigating dense vegetation is common, meaning their feathers take more of a battering than many other species and need refreshing sooner than others. Such birds include marsh wrens and bobolinks.
Marsh Wrens undergo two molts
Smaller birds take around five weeks to fully molt, while the feather-shedding period for larger birds can take up to 12 weeks. Migratory species complete their molt faster, which ensures strong enough flight feathers have developed to enable them to complete their lengthy journeys safely and efficiently.
For parrots, molting is a drawn-out process, taking up to two years to complete in some cases. At the opposite end of the scale, some ducks experience an accelerated molt, undergoing a full feather exchange within just two weeks.
All birds’ feathers become degraded and weakened through general wear and tear, and need to be replaced through molting cycles. Even birds that do not use their wings in flight, such as emus and ostriches molt, replacing feathers that have become damaged over time.
And for some birds, molting isn’t limited to feathers. After the breeding season, puffins shed the colorful outer scales that cover their beaks, replacing them with more muted gray-orange beaks during the winter.
Perched barn swallow going through a molt cycle
During a full molt, a bird’s worn flight feathers are shed and replaced with new ones. While the new set of feathers are growing in, there may be lengthy periods during which a bird is unable to take to the skies efficiently, if at all.
Gaps will appear in wing feathers and tail vital for flight. For some birds, this may happen gradually with only a few feathers at a time being lost. Birds that follow this molting pattern, such as crows and ravens, can still fly, although not as smoothly as usual.
For some waterbirds, such as Canada geese, molting means a period each summer of being unable to fly. After between four and six weeks on land, the new feathers are developed and strong enough to sustain flight.
Red-tailed hawk going through a molt with some missing feathers
During molting, pet birds may appear to be irritable and lethargic. Allowing a bird to rest undisturbed for longer periods will boost their health, and upping protein in their diet gives them strength and energy.
Another way to support a molting parrot or budgie is to gradually increase the room temperature, as a loss of feathers during molting may impact the bird’s ability to keep warm.
Molting itself is not painful, as the feathers that are being shed are already dead and become detached naturally. A bird may feel some slight discomfort as the replacement feathers are developing. These new “pin” feathers initially have a blood supply flowing to them while they are growing, and may be sensitive to touch.
It is usual for a bird’s molt to be completed ahead of the winter, so that they feel the benefit of a warm set of feathers in prime conditions for the coldest months. In winter, some bird species may undergo a partial molt of head and chest feathers, while the primary wing and tail feathers remain in place.
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