The collection contains a number of rare or unusual specimens, including material from endangered or extinct species.
The spirit collection includes one holotype specimen: the White-headed Saw-wing Psalidoprocne albiceps, a species of swallow described in 1864.
It is very unusual for a bird type specimen to be in spirit; of over 8,000 types in the Museum's bird collections (the single largest bird type collection in the world) this is the only spirit specimen.
For some species, our spirit collection includes the only known spirit specimens anywhere in the world.
In particular, this applies to a number of extinct and endangered birds, for example the extinct flightless Fiji Bar-winged Rail Nesoclopeus poecilopterus and extinct Piopio Turnagra crassirostris from New Zealand.
Despite their unique status, rare specimens may still be dissected for research under certain circumstances.
Balancing the appropriate use of the spirit collection against long-term preservation is an important task for curators, and all requests for dissection are carefully reviewed.