Southern boobook smallest owl on the Australian mainland, the southern boobook is long. The nominate subspecies is the largest. It has short, rounded wings and a short tail, with a compact silhouette in flight. Southern boobooks on the Australian mainland follow Bergmann's rule, in that birds from cooler and more southerly parts of the range tend to be larger. Thus, birds from the Canberra region weigh around while those from the Cape York Peninsula and Broome are around . Females tend to be a little larger and heavier than males, with males weighing and females . The southern boobook has generally dark
Southern boobook the nest with food. A purring or braying call is used by both sexes as a contact call around the nest and (more quietly) when bringing food to nestlings, or by the female to beg for food from the male. The female makes a low trill during courtship and nesting. Growls, high-pitched yelps, and screeches can be made when attacking intruders. The southern boobook maintains and defends a territory in breeding season; whether this continues for the rest of the year is unclear. It retires to densely foliated spots in trees in the daytime, each individual often having several roosting