With all this nice weather, I have spent a lot of time in the garden recently, enough time for the local Blackbirds to trust me, there are six of varying ages, feeding and drinking in our shaded ( Under a shrub) "Food Court" , a small water bowl with some pebbles in it, is bringing a lot of visitors, ............I wondered if anyone has seen this behaviour before ? Yesterday the youngest Blackbird, which has taken up residence in a nearby bush, surprised me, by suddenly falling flat on the ground, spreading it's wings and tail feathers, and lying still, after a few minutes, it got up and carried on as normal, about ten minutes later it repeated the same thing......... a quick search on the RSPB site reveals.................
"A male blackbird sits on my flower bed, spreading its wings and fanning its tail in the sun. Is it sick?"
"No, the blackbird is not sick, but you have observed some very interesting behaviour, known as sunning. This usually involves the bird adopting an unusual posture and deliberately positioning itself in sunlight. It may spread or raise its wings, fan its tail feathers, sit down, fluff the feathers on the head and back, and hold the head to one side, looking directly into the sun with one eye. In this country, sunning has been observed in blackbirds more often than any other species (Simmons, K.E.L. The Sunning Behaviour of Birds, Bristol Ornithologists Club, 1986"
No-one knows for certain the reasons birds do this and several theories have been proposed. However, sunning would appear to perform two separate functions: maintaining the bird's feathers in good condition, and helping to regulate it's temperature. There is even a suggestion that they do it simply because they enjoy it!
Precisely how sunning assists with the maintenance of feathers is not known, despite being widely studied. All birds have a gland on the rump, called an oil gland. The 'preen-oil' that this gland produces helps to keep the feathers flexible and hygienic. It has been suggested that the sun affects the preen-oil in the feathers in some beneficial manner, or that it helps to synthesize the Vitamin D from the preen-oil. This preen-oil also aids with waterproofing the birds' feathers. Additionally, the heat from the sun may stimulate activity in parasites within the feathers, making them more accessible when the bird starts to preen. Preening usually occurs directly after sunning.
Cont......
https://ww2.rspb.org.uk/birds-and-wildlife/bird-and-wildlife-guides/ask-an-expert/previous/sunning.aspxAnother article.....
https://www.theguardian.com/environment/2018/aug/16/country-diary-blackbird-entranced-by-the-sun-crook-durham