racing pigeons and hawks

Can anyone offer advice? I recently saw a rather disturbing sign on the back of a pigeon transporter: "Where have all the songbirds gone? Hawks eat them one by one..." seeming to assert that 'hawks' are responsible for the demise of the British songbird and the racing pigeon. It quotes the web address of the racing pigeon royal association. Now, I'm no expert but that seems a little contentious to say the least. The sign implicitly advocates some kind of action but of course fails to specify. Is the RSPB aware of this assertion?  I'd be very interested to know what you think.