The Pied Wagtail is the distinctive British and Irish race of the White Wagtail, a common bird in the rest of Europe. Our birds are blacker than their continental cousins and are present all year round, whereas migratory White Wagtails occasionally pass through our gardens in spring or autumn.
This species is instantly recognisable with its black and white plumage and its long tail that always seems to be on the move.
Pied Wagtails are elegant birds in constant motion, darting here and there to pick up tiny insects from the grass. This behaviour makes them conspicuous in a garden or town centre, but in the more natural habitat of the shadows by a flowing stream they can be hard to spot.
Natural roost sites are generally in reed beds, where the water below the reeds helps to keep the birds warm and also means that ground predators are kept away. Pied Wagtails flock together to roost for a variety of reasons. A good warm place is hard to find so it makes sense to share it. Also there is safety in numbers and, amazingly, the roost acts as an information exchange. Birds which are having difficulty in finding food simply follow the birds that are in better condition in the morning.
Other roost sites include man-made structures. Hospitals are popular, having lots of enclosed courtyards with nice shrubs planted in them. These are sheltered and make excellent roost sites. Others include the cooling towers of power stations, machinery in sewage treatment works, factory roofs, heated greenhouses and large supermarkets. About 10% of our gardens, usually those with larger lawns or ponds, have them as regular garden visitors. This will go up to a third or more in cold winter weather.
Note the pronounced spikes in garden use in cold winters.