I've never had Ostrich burger but I do remember years ago that Sainsburys used to sell Ostrich steaks. Very tasty they were too and very low in fat and low in cholesterol.
I seem to remember the meat being a similar colour to beef.
I eat them again anytime.
Had crocodile steak and crocodile sisig at Davao Crocodile Park both pretty tastless and too tough for my liking.
The croc steaks I had in South Africa were much better if my memory is good.
Or maybe the extra pint of beer only made me think so