In February 1842 Gilbert returned Australia to collect further specimens. He reached Perth in July and stayed for 17 months in Western Australia. He made his most interesting discoveries among the Wongan Hills, about 100 miles north-east of Perth. He was a fine naturalist and his notes on birds, their habits, diet, song and the names given them by the aborigines were all of great interest and value. Gilbert collected specimens of 432 birds, including 36 species new to Western Australia. He collected 318 mammals, including 22 species not previously known in the west. By the end of January 1844 he was back in Sydney and during the next six months worked his way to the Darling Downs in Queensland.