‘Sunbathing’ is used by some birds as part of their routine feather maintenance and is most commonly seen by Garden BirdWatchers in Blackbirds and Robins. The birds invariably adopt a posture in which the body feathers are fluffed up and one or both wings are held out from the body, with feathers spread. It is thought that using the sun in this way does two things. It both helps the preen oil to spread across the feathers and drives parasites out from within the plumage. Some of these parasites feed on the feathers themselves and all are highly specialised, with many only found on a single species of bird.
The plumage of a bird is important, providing both insulation and flight, and individual birds spend a significant amount of time looking after their feathers. In Bird Table 59 there was an article on moult, and moult is clearly an important component of feather maintenance, with worn-out feathers replaced by new ones as part of a regular cycle. More routine maintenance happens on a daily basis and involves a combination of preening and bathing.
Preening involves manipulating individual feathers with the bill, often realigning the filaments that hook together to hold the feather in shape. Watch a Blackbird doing this in your garden and you will soon see how the bird works each feather in turn, carefully ‘nibbling’ the feather. Some species indulge in mutual preening; known as ‘allopreening’ this is usually seen in birds that are paired, the preening behaviour thought to strengthen the pair bond.
Most birds also indulge in bathing, either using water or dust/sand to clean the feathers. A garden bird bath can be a real draw in the hot summer months and it is worth watching how the different species bathe. Most stand in the water, often thrusting down and forward with their head to force water up onto their back. The aim is not to completely soak the plumage but to wet it sufficiently so that the plumage can be cleaned. Other birds will ‘shower’ by using the dew or raindrops that collect on vegetation, again wetting but not soaking the plumage.
Dust-bathing is less common in garden-visiting birds than water-bathing and is more often associated with species that live in dry habitats or in open landscapes. House Sparrows, pheasants and partridges, however, are very fond of dust-bathing, reflecting their dry-country origins and may be seen engaging in this as a communal activity. House Sparrows, in particular, work the dust into their plumage by using flicking movements of the wings.