In recent years it has become clear that hidden amongst what was once thought to be one species there are sometimes one or two other cryptic species that , had it not been for genomic studies, would have remained undiscovered. These cryptic species may have diverged many millennia ago and then evolved to resemble another species from which it can now not be or hardly be distinguished on external characters alone.
But recently I read two papers that were a complete eye-opener to the hidden complexities of some of these relationships. You can read these for yourselves here and here. I have included two extracts below from the first paper to whet your appetite and if you haven't read them already this will have you scrabbling to do so.

And this which I find absolutely mind-boggling. You can only imagine the excitement and incredulity of the guys that discovered this. Hats off to them.

I'm pleased to be able to post some wonderful pictures taken by our good friend Karlos Ross at Holguin Birding of a female Least Bittern (Ixobrychus exilis). It is said to be a common and widespread permanent resident in Cuba but we have only seen it a couple of times in Cuba, and then only in flight. They are found in marshes, swamps and pools with dense vegetation and also in mangroves but are shy and retiring so are difficult to photograph. Well done Karlos.