Early settlers coined the name Dollarbird, because the roundish white patches on the underwing of the bird you see during flight, resembled silver dollar coins. The bill and feet are orange and the feathers are blue-violet and blue-green, though not evident in my images.
The Dollarbird is the sole Australian representative of the Roller family, which have a rolling courtship display flight.
The Dollarbird arrives in northern and eastern Australia in September each year to breed. In March or April the birds return to New Guinea and adjacent islands to spend the winter.
The call is a grinding , metallic, buzzing.
At the cottages the birds are seen high in the trees, so I apologise for the low quality of the photos I have taken below. The second photo shows a bird in flight, and you can see the white patch under the wing.