Courts Island is a dolerite

Diabase

Diabase or dolerite is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. In North American usage, the term diabase refers to the fresh rock, whilst elsewhere the term dolerite is used for the fresh rock and diabase refers to altered material...

 island with an area of 15.83 ha

Hectare

The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...

 in south-eastern Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. It is part of the Actaeon Island Group, lying close to the south-eastern coast of Tasmania

Tasmania

Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...

, at the southern entrance to the D'Entrecasteaux Channel

D'Entrecasteaux Channel

The D'Entrecasteaux Channel is a region of water between Bruny Island and the south-east of the mainland of Tasmania. It extends between the estuaries of the Derwent, and the Huon Rivers...

 between Bruny Island and the mainland. It is connected to Bruny Island by a spit

Spit (landform)

A spit or sandspit is a deposition landform found off coasts. At one end, spits connect to land, and extend into the sea. A spit is a type of bar or beach that develops where a re-entrant occurs, such as at cove's headlands, by the process of longshore drift...

 at low tide, and is part of South Bruny National Park

South Bruny National Park

South Bruny National Park is located on Bruny Island, Tasmania, Australia, about 50 km south of Hobart. The park contains the Cape Bruny Lighthouse. The highest point of the park is Mount Bruny at 504 m...

.

Fauna

Recorded breeding seabird

Seabird

Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...

 species are the Little Penguin

Little Penguin

The Little Penguin is the smallest species of penguin. The penguin, which usually grows to an average of in height and in length , is found on the coastlines of southern Australia and New Zealand, with possible records from Chile.Apart from Little Penguins, they have several common names...

, Short-tailed Shearwater

Short-tailed Shearwater

The Short-tailed Shearwater or Slender-billed Shearwater , also called Yolla or Moonbird, and commonly known as the muttonbird in Australia, is the most abundant seabird species in Australian waters, and is one of the few Australian native birds in which the chicks are commercially harvested...

 and Sooty Shearwater

Sooty Shearwater

The Sooty Shearwater is a medium-large shearwater in the seabird family Procellariidae. In New Zealand it is also known by its Māori name tītī and as "muttonbird", like its relatives the Wedge-tailed Shearwater and the Australian Short-tailed Shearwater The Sooty Shearwater (Puffinus griseus) is...

. Feral cat

Feral cat

A feral cat is a descendant of a domesticated cat that has returned to the wild. It is distinguished from a stray cat, which is a pet cat that has been lost or abandoned, while feral cats are born in the wild; the offspring of a stray cat can be considered feral if born in the wild.In many parts of...

s are present.