Because this guy was able to fly around the zoo at will, I suspect that it was perhaps a freeloader and not part of the actual exhibits. Two of them would chase each other for a while and then alight in the trees above one of the bird exhibits.
Shooting at the SD zoo actually presents quite a few challenges, mostly because of fences and mesh screens and the like between you and the animals. Additionally some of the exhibits are mostly behind glass, as was this one. For the ability to get up close and personal with tigers and polar bears, I’d rate the Detroit Zoo much better than San Diego.
If you look closely at the right edge of this image you can make out the outline of the chain link fence through which this photo was taken. Using the right settings I was able to find a spot that worked for this face-on shot.