I think it is more likely to ensure “safety in numbers” especially while in flight. A lone individual is more likely to be mobbed by a nest host species (currawong or magpie) or preyed upon by a predator (large raptor) than one that is part of a flock. An individual calling as it takes flight alerts others to follow. Calling while in flight keeps individuals within a flock close together, especially if they are flying at night.
Dr Stephen Ambrose Ryde NSW
