Nature Watch: Where do all the birds go at night?

Dec 24 2010 By Rhian Davies – RSPB Volunteer

As the gloom grows and the curtains are closed on the now deserted garden, have you ever wondered where birds go on these long winter nights?

Each evening, birds must find a roost that keeps them safe from predators and protects them from the worst of winter’s bite.

Birds are surprisingly well equipped to survive cold weather. Rain and snow is repelled by the outer feathers which are coated in waterproof oil. Underneath, are downy feathers which, when fluffed up, trap warm air like a duvet, keeping them insulated from the chilly surroundings.

Severe conditions however, can force birds to adopt sociable bedtime habits and so they will roost communally. Long tailed tits roost throughout the year in the family groups they live in. They perch on a twig, squashed side by side, with dominant group members sandwiched in the warmest middle spots. Wrens will cram into a nestbox to share body heat, with 61 being the record number of these tiny birds cosying up together! Sleeping this close to a roost mate though can ruffle a few feathers. Feathers risk being damaged, and disturbed and can lose their important insulation. As a result, it is rare for birds to roost in close contact. So why do birds roost communally, if not for warmth?

A popular theory is that there is safety in numbers. An individual blackbird in a flock of hundreds is less likely to be caught by a hungry predator, but large numbers of birds will attract more predators. The opportunity to gather tips on the best places to dine is now thought to be the main advantage of sharing a night time retreat. Birds can check the condition of others entering the roost and if they look well fed they know who to follow the next day. Knowledge like this during winter can be life-saving even if the night’s sleep is less peaceful than normal.

Some savvy species take advantage of heat sources created by humans. Pied wagtails are known to congregate in their thousands to roost in the sauna-like conditions of power station cooling towers. The most famous of our communal roosters, the starling, will commute into cities in the evening, where temperatures are typically higher than in the surrounding countryside. House sparrows build a nest for winter and often site them in buildings, next to warm air vents or on streetlights. Becoming a carpenter is time consuming and nests can be taken over by squatters, so roost construction is rare.

We may not be able to see the birds once the curtains have closed, but we are beginning to understand the complex organisation and behaviours they are capable of. If you want to find out more about how you can help birds in the freezing weather conditions visit http://www.rspb.org.uk/advice/helpingbirds/.