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
Australasian gannet with white overall. They have dark brown bills, bare facial skin and eyes, and dark grey legs and feet. Australasian gannets take 2-5 years to gain adult plumage. Over this period, the upperparts and underparts gradually whiten and the crown and nape become buff-coloured. However, there is great variation in the age that mature plumage is seen. This species is distinctive, and only likely to be confused with species that do not generally share its range. The Cape gannet is a rare vagrant to Australasian waters and has an all-black tail, while the masked and red-footed boobies are generally restricted