What is Moulting and Why do Birds Moult?
It's a strange thought to imagine garden bird species without feathers, but some do shed their feathers to allow new, healthier ones to grow.
Moulting is simply when a bird sheds their feathers to make way for another year of their adult plumage. Just like our hair, feathers get damaged, and these damaged feathers need to be replaced so that birds can efficiently keep their temperature right, fly, protect themselves and take part in courtship displays.
In this guide, we will go through why birds moult, when they moult and birds that you might spot that look a little bit strange.
Why do Birds Moult?
Moulting is the process in which birds shed old feathers and new feathers grow. Over time, body feathers become worn, damaged and inefficient, so they need replacing.
Replacing feathers helps maintain insulation, flight efficiency, and camouflage; its moulting is essential for survival, avoiding predators, and preparing for the next breeding season.
Some birds also moult to change to adult plumage or breeding plumage.
How Does a Bird's Appearance Change?
During moulting, birds tend to look scruffy, dishevelled and patchy as they can moult flight feathers, wing and tail feathers; they never lose all their feathers at once. Missing feathers can make birds look thin or even flightless temporarily.
It's also a time when young birds shed their juvenile plumage to reveal adult feathers, transitioning from dull-coloured to vibrant hues. Colour changes may also occur in adults, such as shifting from dull to bright breeding colours in males.
When is Moulting Season?
Most UK garden bird species moult in late summer or autumn, so it's post-breeding season. Seasonal changes and temperature can affect the exact timing at which moulting takes place. But the end of summer is when the weather is warmest and the bushes are at their fullest, so they have plenty of good weather and food to help them through this vulnerable time.
For some migratory species of birds, spring moult may occur before the breeding season. The actual moult can take up to several weeks, depending on the species and type of moult.
Garden Birds that Moult in the UK
Blue Tit
Undergoes a complete moult after breeding in late summer; often looks especially scruffy during this time.
House Sparrow
Moults into fresh feathers after breeding; males may appear duller until new plumage fully comes in.
Robin
Moults quietly and becomes very secretive; both adults and juveniles change into new body feathers.
Blackbird
Undergoes a partial moult in spring and a complete moult in late summer; tail and wing feathers are replaced.
Great Tit
Like blue tits, they experience a complete body and flight feather moult after breeding.
Goldfinch
Moults gradually and often keeps a tidy appearance, but may look slightly thinner during the moult.
Chaffinch
Completes its annual moult between July and September; males transition into brighter plumage for winter.
Greenfinch
The Greenfinch moults in late summer; males and females both lose some of their brilliant green feathering temporarily.
Starling
Undergoes a dramatic moult after breeding; new feathers give them a spotted winter look.
Dunnock
Moults discreetly and remains hidden during the process; gains a fresh, subtle plumage.
Wren
Replaces worn feathers after breeding; rarely seen moulting due to its secretive nature.
Collared Dove
Undergoes a long, gradual moult of wing and tail feathers to avoid flight impairment.
Woodpigeon
Has a prolonged moult period, sometimes almost year-round, replacing feathers bit by bit.
Song Thrush
Completes its moult by late autumn; juveniles moult into adult plumage in their first year.
How Often do Birds Moult
Most birds only moult once a year as part of their annual cycle, but some do undergo a partial moult more frequently.
Migratory species may also moult twice: once before and once after migration.
Are there any Seasonal Changes to Behaviour?
During the moulting season, you may notice you see less of the beloved local garden birds; this is because during this time, many species become more secretive and less active to avoid predators, as a bird's plumage protects them from a lot. If they have shed their flight feathers, foraging and feeding can become harder.
They'll also be less bird song, as they try to conserve energy to spend on growing feathers back. This does mean they may visit accessible bird feeders and bird tables, as when birds undergo a moult, they need high-energy food.
How Can You Help During the Moulting Period
The moulting period can be hard for birds, but there are some ways we can help!
On clean bird tables and bird feeders, provide high-protein foods, like mealworms and sunflower hearts, as this will help to aid feather growth. It's also best to keep a bird bath, or shallow dish, full of fresh water for drinking and bathing.
If you can, create shelter for the birds; this can be nest boxes or just leaving bushes untrimmed, as they like to have safe hiding spots during this time.
