From Final Fantasy Wiki
Condors are a species of giant birds in
Final Fantasy VII. They appear to be physically similar to real world condors, only hundreds of times larger. Only one fully-grown Condor is ever seen in the game, nesting its egg on top of
Fort Condor. This Condor stays stationary, protecting its egg until it hatches.
Shinra sees the Condor as a threat to its
Mako Reactor operations, so tries to push the bird off. A group of resistance fighters decide to protect the rare Condor species and garrison Fort Condor to oppose Shinra.
The series of battles become the
Siege of Fort Condor. After the final battle, the Condor on top of the fort dies in a flash of light that shows the wings of a Phoenix. Afterward, the egg hatches and a baby Condor is born, along with a
Phoenix Summon Materia. It flies off, showing that the species will continue to survive. As of yet, Condors have not returned in any game of the
Compilation of Final Fantasy VII. Though since they are endangered, it is not too large of a surprise.