I heard about it on the David Attenborough's Galapagos series:

https://iview.abc.net.au/show/david-attenborough-s-galapagos

Here is a YouTube playlist, I think it was episode 3, Evolution:

https://www.youtube.com/playlist?list=PL3iXsS5tZSZG4gcYrblBd...

Also see the wiki page mentioned in the sibling comment.