Some places in the bible we see mention of foul that come to war and battles. The literal term can at times mention an Eagle yet describes a vulture.("The Hebrew nesher, meaning "to tear with the beak," is almost invariably translated "eagle," throughout the Bible; yet many of the most important references compel the admission that the bird to which they applied was a vulture"-  Eagle in the Bible Encyclopedia - ISBE) (Bullinger compares/relates Matt.24:28, Job 39:30; 28:7, Lk.17:37, Rev.19:17-21, Hab.1:8, Hos.8:1 )  

(ISBE- " There were many large birds and carrion eaters flocking over Israel, attracted by the offal from animals slaughtered for tribal feasts and continuous sacrifice. The eagle family could not be separated from the vultures by their habit of feeding, for they ate the offal from slaughter as well as the vultures. One distinction always holds good. Eagles never flock. "/ Is.34:15) These people may not have had all the classifications we have to day of birds of prey such as hawks, eagles, vultures, falcons, (Hebrew `ayyah rendered-) kites (Is.34:15/ Lev.11:14/ Deut.14:13) , osprey and described them alike.

I have read (looking for the source) how vultures were often called war eagles thus the figurative use of Eagle to mention them.