The bustard is beautiful. I never saw one (unless I overlooked it in one zoo or another). The largest tom turkeys are not much bigger than 20 kilos. As for roosters, I'm not sure. They can be quite large, but by no means so heavy as bustards. Since they're also lean, I'd guess no more than 4 kilos, and that would be for the full-size breeds.
The old drawing I posted
comes from
Délos X, which is a century old. The vase it
comes from dated from the very beginning of the 6th c. BCE. The decorators loved doing cocks; there are hundreds and hundreds known.
Pat L.