Soppy pigeon getting hurt

Hi,

A pigeon has been coming intermittently into our garden. He is extremely nervous, especially when our dog is around ,and has really sparse head and neck feathers. Today, a much slimmer, fitter pigeon cornered him, until the original pigeon hid in some leaves in the corner. The alpha pigeon followed him into the corner and starting pecking him whilst cooing. I am worried the meek pigeon will get injured further,as it only dawned on me today that his sparse feathers are because he is being attacked.

Any advice apreciated, thanks Blush