I spotted this Blackbird during a wander along the woodland trail in Cardiff’s Bute Park today, and it was concentrating so hard on its sunbathing that it didn’t notice me at first.
The sun was fierce, which I think accounts for the bird sitting with its mouth open, trying to cool itself down. As for the sunbathing itself, here’s the explanation from the British Trust for Ornithology website:
‘Sunbathing’ is used by some birds as part of their routine feather maintenance and is most commonly seen … 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.