Just over the last couple of days I have been hearing the distinctive call of the Common Koel around my house and then on Tuesday I was lucky enough to see a female and male in the trees in my back yard.
These birds are migratory and return to the east coast of Australia between September and October each year and return north in about April. The Birds in Backyards website reports that this species is a parasitic breeder, which means that it doesn't actually raise its young but rather lays its eggs in other bird species nest tricking them into raising the young Koel. Fairly amazing since some of the bird species the koels do this to are quite often significantly smaller, which means that end up raising a baby that is monstrous compared to themselves. Bizarre.
If you have these birds in your backyard you can record their presence on the the Birds in Backyards survey for this species. The information helps to create a picture of their distribution and presence in Australia. The web address is: http://birdsinbackyards.net/surveys/koel.cfm. This site also has recordings of their calls which will help you identify them by call if you can't physically see them.