What is a kookaburra, as inferred from the passage?

Directions: Read the passage and answer the question that follows.

While hiking in Carnarvon Gorge in Queensland, my family and I noticed a small group of birds diving in and out of the branches of a gum tree. They were chirping very loudly and obviously in distress. We could see a nest in the branches with baby birds inside and a very large goanna walking up the tree trunk, having eyed what he wanted for lunch. The small birds were desperate to chase the goanna away but had little hope because of their size. As we were contemplating what to do, a kookaburra flew down and thumped the goanna very solidly in his side, knocking him off the tree trunk. The small birds quickly settled down to care for their young.