Very tame Buzzard (I think). Visiting my garden daily

I have a Buzzard who visits my garden daily since Christmas Day.

it is very tame as in I can walk up to it and it will only fly off when I am 5ft away. It appears healthy but as it is cold and fluffed up hard to say about it’s weight. 

I am concerned it may be unwell or a captive bird that has made my garden home.  I want to  do what’s best for it but this is a garden visitor far removed from what I know about. Any advice greatly appreciated.