The Capricorn and Bunker Cays form part of a distinct geomorphic province at the southern end of the Great Barrier Reef.

The sea level was much lower during the last Ice Age (at the end of the Pleistocene period) and the coastal plain on which today's reefs and cays developed was completely exposed.

[6] In 1803 Captain Eber Bunker of the whaling ship Albion was the first European to discover the region and gave his name to the southern group.

The southern cays and reefs were first chartered between 1819 and 1821 by Lieutenant Phillip Parker King of the Royal Navy initially in Mermaid and later in Bathurst.

The naturalist, Professor J. Beete Jukes, was on board Fly and his published journal provides valuable information on some of the cays.

[7] It is unsure if the project ever succeeded in the removal of guano from Hoskyn Islands, but as can be seen from the below newspaper article the company intended to remove a significant quantity of the accumulated droppings of innumerable birds for use as a fertiliser: The Barrier Reef Phosphate (Guano) Syndicate interests on the north-east coast of Queensland have been taken over by Phosphates Pty, Ltd, a private company formed with a capital of £10,000 to work guano deposits and exploit other products The Bunker Group includes Lady Musgrave, Fairfax, and Hoskyn Islands, as they run m that order north of Lady Elliott Island The new company has secured leases of Fairfax and Hoskin, and the right to remove guano there from.

From the report of the company's surveyor it appears that there are 20000 tons of guano available for immediate exploitation, and samples analysed by Mr John D. Spence, PCS, are said to show the component parts of nitrogen and phosphoric acid to make it of commercial value as a phosphate fertiliser which could be used as a base in the manufacture of complete compound fertilisers.