"It wasn't as if it were two different species colonizing and becoming flightless. This was the very same ancestral bird." Does "very same" mean identical? So same DNA?
The 2 flightless rails that evolved were different species, but they both evolved from the same species
(Dryolimnas cuvieri). The title is misleading since the second flightless rail is not exactly the same as the first, it didn't come back from the dead. But the part you're quoting is correct, the
ancestor of both was the same. Iterative evolution is when 2 similar species evolve in the same group, but in this case, they weren't just both in the rail family, they both came from the same rail species.