How many species of kookaburras are there?

There are two species of kookaburras in Australia;

Laughing dacelo laechii

and the

Blue-winged dacelo novaeguineae.

In total, there are four known species of kookaburra. The other two species live on the island of New Guinea and some Indonesian islands. These varieties do not have the characteristic laugh of the Australian kookaburras.