So he's observant enough to figure out that much. Not that he expected Casper to be stupid, but he's dealt with too many people not to have his expectations be at rock bottom. Congratulations for clearing the lowest bar ever.

Anyways, the confidence must mean he's prepared even for the possibility of being jumped by several beasts, so now the drifter is curious about exactly how strong the man before him is.

"Ah, but can you be sure a beast here would act the same as a beast from your world? It only takes one lapse in judgement."

Although, he did say we, so maybe the bird has some sort of combat ability as well...