Is this pigeon poorly?

hello Wave 

I feel a bird food mix and get a variety of birds. Recently this city pigeon has been coming and it sits for ages on our roof, usually all fluffed up with its head tucked in. 
it does eat when I put food out so I wondered if it is sitting waiting for food sometimes? I’m worried it could be ill. However I could be wrong, it might just be enjoying a chilled spot to relax (we’re in a quiet corner of central Glasgow)