The middle finger is called a bird because birds have a long association with taunting.
The same reason Americans do. Because it's only one finger (the middle finger) used when flipping the bird.
Pigeons have been trained to carry messages in the past.
parrot
Your middle finger.
No, a humming bird's wing will not hurt your finger.
robin
geese
it means to use your finger to sling the bird to hit the pig.
Falconry is the sport of hunting with a trained bird of prey.
jump
Place your finger against the front of the bird's legs and he will instinctively step up.