Takeaway: Have you ever seen a bird that seems to have lost many of its feathers? This is likely moulting, a natural process that helps birds stay healthy and fly efficiently.
Feathers are critical for birds not only for flying–they are also used to regulate body temperature. They can trap heat in cold weather or shed warmth when it’s hot. They also contain oil secreted by the preen gland that makes them waterproof so they do not become waterlogged and heavy. Feathers are also essential for flight, display, and camouflage.
But what happens when birds lose their feathers–especially on their head? If you’ve ever seen a scruffy-looking or nearly naked bird in your smart bird feeder and wondered if it was sick or injured, you’re not alone. But that haggard-looking bird is likely moulting, a natural process that helps birds stay healthy and fly efficiently.
Let’s look at moulting in more detail to understand what it is and why it happens.
What Is Moulting?
Moulting is when a bird sheds its old feathers and grows new ones. Feathers wear down due to sunlight, preening, weather, and everyday use. In order to remain healthy, birds periodically shed old feathers so new ones can grow.
Most birds moult once or twice a year. It generally takes place in a controlled, orderly fashion. Feathers are lost and regrown gradually so the birds can continue to fly, forage, and evade predators. But in some extreme cases it happens all at once–keep reading to learn about that less-common process.
Why Do Birds Moult?
Birds moult for several reasons:
- Feather maintenance: Old, worn feathers can be brittle, meaning they lack proper shape, aerodynamic properties, and wing area.
- Seasonal needs: Some birds have different coloured feathers for breeding and non-breeding seasons.
- Growing up: Juvenile birds moult their baby feathers as they become adults.
- Health and hygiene: Old feathers can be damaged or have parasites.
What Is Catastrophic Moulting?
While most birds moult in stages, some undergo catastrophic moulting. In this event, large groups of feathers, or even all of a bird’s feathers, shed at once, making the birds temporarily flightless. While it sounds (and looks) bad, it’s a normal part of their life cycle.
Moulting in UK Birds:
- Blue tits look ragged in late summer: Blue tits replace their feathers even as they raise their chicks.
- Blackbirds can lose all their head feathers at once: In a classic case of catastrophic moulting, blackbirds temporarily become bald.
- Robins change color: Juvenile robins are speckled brown but moult into their red breast come autumn.
- Starlings get a makeover: After their late summer moult, starlings emerge with iridescent purple and green feathers.
When Do Birds Moult?
Birds usually moult once or twice a year. The main moulting period is in the late summer or fall, after the breeding season has taken place. Some birds may also moult in the spring to replace head or body feathers.
- Timing depends on the species
- Habitat, season, and bird age/life cycle influence moulting patterns
- Different species of birds undergo partial and complete moulting
Are Bald Birds Sick?
If you see a bird in your garden that is bald or looks scraggly, don’t assume that it is sick or in trouble. If it is otherwise active, alert, and feeding, it’s probably just moulting.
If your bird feeder cam shows several birds moulting, you can:
- Provide food: Moulting takes a lot of energy! Fill your feeder with high-protein foods like mealworms or sunflower hearts.
- Provide water: A birdbath with clean, fresh water helps birds stay hydrated and cool when it’s warm.
- Give them space: Don’t stress these birds out by getting too close. Instead, enjoy them from your bird feeder camera.
Moulting may not be pretty, but it’s normal and important for the birds that use it. ture has all sorts of strategies for survival–even if they look strange to humans.