In the picture you will see a picture that is obviously difficult to get. Here the eagle is hunting a flock of bats. It is a great picture where the eagle is frozen in time exactly when it is about to grab hold of its meal. Its wing span shows how big a bird it is and how powerful it can be.
The bats come out in large numbers for a lot of reasons and it is usually for feeding. Flying ants can be one of the reasons the bats are circling in any place. Their large numbers make them a easy target and predatory birds like the eagle in the picture will take full advantage of this. The flock in the picture has at least a hundred bats and are probably looking for a meal unaware that they could be one. 
