Worried about this pigeon. Please help.

Hello

There is this pigeon who visits my garden in the morning for a feed. I've noticed he makes this noise and it is concerning me. I noticed this 3 days ago and thought it was gone but he's back doing it again. He stops making the noise when eating but as soon as he stops and wanders, he does the noise again. You'd have to listen real close to your phone speaker up loud to hear as he was on the roof at this point (but obviously only if you can't hear it at first). 

Is it anything to worry about? Any advice on how to contain to get help if so?

Thanks 

Sharon