it would appear that the ball it sits on is two piece.the top half includes the legs.screw would attach to tail from inside upper half of ball.these were also used as stove top finials,weather vane,flag pole,mail box...you name it.the shape of tail nails this for me.see again my upper post with this in mind.
a simple guess
It would appear it is indeed a finial.the unfinished legs acomodate any application.this one is veery close if not it...View attachment 1134136and yours..View attachment 1134137
I don't doubt that it is some sort of finial but it seems odd that the screw is short and does not go through the tail. It would be difficult to screw it to the inside of the globe's upper half. Most flag or weathervane eagles that I have seen are either made one piece with the globe or are screwed to the globe from under the eagle...like the buttocks area. At least that has seemed to be the easier way to affix them together.