How do you get a bird to land on your arm?

Persuade the bird that 1) you're not going to grab it and eat it; 2) it can find food there. Depending on how wary the bird is normally, it's going to require a small amount of food and a large amount of patience. One tip: if one does land, or seems about to, don't swallow; to a small animal, that means you're moistening your mouth for a bite.