Rhino City

As I woke this morning, I tuned in to The Blackbird who is always singing out the back, perched high in the neighbour's tree.
'Rhino City, Rhino City', it chorused, with different verses in between.
Gradually, its song plan became apparent, and I could anticipate when it was going to sing the chorus again, even when it changed the melody, length or words of the verses.
Isn't that weird?