The bison live peacefully with most animals on the ranch, but, when a pair of geese decided to land near the herd, one young female wasn't having it.
She persistently walked both geese off the field. The geese mounted no opposition.
Why exactly the bison chose to chase the geese off is a question I can't answer for certain, but it seemed a very fitting behavior for a bison to do that. I know she wasn't threatened by the geese and they probably weren't annoying her. My guess is that she chased the geese for amusement.