The RAAF HS-748 navigation trainers were known as 'Draggies'. Conversely, the two 748s operated by the Royal Australian Navy were known as 'Speedbirds'; probably in comparison with the Grumman Trackers that the squadron, VC851, also operated.
Maybe it was called the Budgie because of the Darts' whistle??
I flew both the RAN 748s and Ansett F27s, and have fond memories of both.