As you try and make your way accross the river to the road to Bastion Falls you come accross a giant vulture. You then remember a thing Frank once told you:
“Like Reverend Grant always says, Wilson: some creatures only speak the language of the gunshot…”
You must go back to the church. Nest to the door is a shotgun that Reverend Grant put just in case. Pick it up and return to the vulture. Cock the gun and shoot it into the air. This will scare away the vulture and allow you to pass.