5 Islands Puzzle - Solution

The Puzzle:

There are 5 Islands in a row. Parker the Paranoid Pirate has a ton of gold hidden on one of them.

During the day you have enough time to sail to just one island to find the gold.

But every night Parker moves all that gold exactly one island over (so if it was on island 4 it gets moved to either island 3 or 5)

What strategy can you use to have the best chance of finding the gold?

Is it possible to be sure of finding the gold?

(Try this puzzle with a friend, one of you can be Parker)

Searching islands 2, 3, 4, then 2, 3, 4 again is guaranteed to find the gold. Amazing hey?

It helps to know that the gold alternates between even and odd islands.