Kick the guard in the nuts, take the weapon and shove it into the birds brain
Kick the guards ass and use his fibula to whack the bird on the throat so she will open her mouth and pry it's mouth open with the dead guards fibula and jump out
Go back down to the stomach and grab the guy and throw him on top of the guard and if the guard used his spear on him he is now defenseless so beat him down and pry the birds mouth open with the bodies lying around (after stomping on her throat)