Carl Hunstein emigrated to America and traveled across San Francisco to New Zealand. From 1885 until his death he worked for the New Guinea Company. Hunstein discovered several paradise birds, including the named after the German scientist Adolf Bernhard Meyer narrow tail scimitarbill ( Epimachus meyeri ), the Princess Stephanie Bird of Paradise ( Astrapia step haniae ), the Blue Bird of Paradise ( Paradisaea Rudolphi ) and the Emperor Bird of Paradise ( Paradisaea guilielmi ).
On 5 and 6 April 1886 Hunstein was a member of a US-led Eduard Dallmann expedition to explore the Sepik. On a trip with a barge about 76 km upstream of the participants of the expedition explored the possibility to navigate the river with steamboats. From July 29 to August 10, 1886 took Carl Hunstein in economic geography and a botanical expedition to the Sepik on the steamer part Ottilie, who led the Governor of the New Guinea Company, George of Schleinitz. The trip, which was also the botanist Max Hollrung and the astronomer Carl Schrader were involved, led 650 km upriver almost to the Hunstein Mountains. Hunstein, Hollrung and the geologist Carl Schneider repeated the trip under the direction of Carl Schrader July to November 1887 the steamer " Samoa " and was about 800 km drive on this trip the river far upstream. Carl Hunstein in 1888 with a Mr. von Below, a coffee planter from Celebes, killed by a formed on the Ritter Island at the outbreak of the volcano tidal wave on the southern tip of New Britain.
In his honor, the Hunstein Mountains were and Mount Hunstein ( Hunsteinspitze ) in Papua New Guinea, as well as a number of native plants and animals there including the members of the family of finches Hunsteinnonne ( Lonchura hunsteini ) and named the tree fern Cyathea hunsteiniana.