Gilbert is often cited in the earliest descriptions of many Australian animals, many of which were unrecorded in European literature, and some of these are named for him by those authors.
Gilbert was sent to the newly founded Swan River Colony and made collections and notes on the unique birds and mammals of the surrounding region.
He later joined expeditions to remote parts the country, continuing to make records and collections until he was killed during a violent altercation at Mitchell River (Queensland) on the Cape York Peninsula.
The party landed in Hobart, Tasmania in September, and in January, Gilbert and Gould traveled overland together to Launceston.
Gould decided they should separate and sent Gilbert off on 4 February 1839 to the Swan River Colony, assuring him that he would look after all his personal possessions which were still in Hobart.
He met Francis Armstrong within a few days, who was acquainted with the Nyungar peoples of the region, and began to make collections in the area around the Swan River and York.
His arrival began a period of ornithological research that saw a large number of his specimens described and depicted by the Goulds, many of which were "discovered", the field notes that accompanied these gave details of birds of the west that allowed inclusion in their ambitious publication.
Taking one servant with him, Gould visited New South Wales and was made welcome by his wife's family, the Coxen's and other wealthy landlords.
Almost immediately, Gould set off again, this time for South Australia, where he met the Governor and accompanied Charles Sturt on his expedition to the Murray Scrubs.
Gilbert had provided Gould with thousands of specimens of every description, from quadrupeds to insects, from shells to crustacea, from plants to reptiles, but mainly and most importantly, birds and eggs.
He had provided Gould with over 60 new species of birds, including the extinct paradise parrot which he first discovered in the Darling Downs in June 1844.
[3] There still exists some controversy over his death – the wound was apparently smaller than a spear, and some suggest he died from an accidental shooting by one of his companions.
He was buried on the spot, a tree nearby was marked, and a fire was lit over the disturbed earth to screen the grave; this, although much searched for, has not since been found.
John Gilbert's memorial at St James' church is inscribed with the Latin phrase Dulce et decorum est pro scientia mori, which may be translated as "it is sweet and fitting to die for science."