I was imagining the bird fighting back with your own spear...
But truly, the thing that sticks out to me is that the spear is rather balanced in the bird's neck. I imagine that if it had pierced a bit less, or a bit more, it could have thrown off the bird's center of gravity too much to achieve stable flight.
This is exactly classic survivorship bias, right? It's the kind of thing that usually works for the hunter (or they'd have learned not to do it), and the bird surviving to be observed far away is a combination of rare circumstances...
But truly, the thing that sticks out to me is that the spear is rather balanced in the bird's neck. I imagine that if it had pierced a bit less, or a bit more, it could have thrown off the bird's center of gravity too much to achieve stable flight.