It's amazing how many scams there are, and unless you know what people look like you don't know it's a scam. Somebody was claiming to be selling their military Macaw named Cash in Winnipeg, MB a while ago. The picture was of Dave Womach... pretty sure he's not selling Cash in Canada...
So a quick report and it was removed. All you can do is let the people running the website know and advise the person who owns the birds if you know them personally. People usually use pictures of people from other countries, of course somebody from Canada is going to be going on a UK site to check the classifieds so it's highly unlikely that they will get caught.