Evolution

Ok - I think I understand it now. Darwin saw very similar finches on neighbouring islands, but each island had different kinds of nut trees, and the finch beaks were adapted for the particular nuts.

Yes, that's it.

So, originally, a load of finches live on one of the islands, and eat the nuts there.

Yes

And at some point, a few of them fly to a neighbouring island, or get blown there in a storm or whatever.

Yes

Their beaks evolve so they can eat the nuts on the new island.

That's right.

So eventually there are two species, very similar, but on adjacent islands and with different beaks.

Yes

I think I understand!

Hooray!

Just one thing.

Yes?

Whilst they were evolving on their new island home, what did they eat?

Er . . .