Which petrel is this? A tale of polar explorers and a little seabird’s name

This month, Curator Vertebrates Alan Tennyson and the Department of Conservation’s Johannes Fischer, published a scientific paper that clarified the identity of a common subantarctic seabird. Alan explains why this was necessary and what a surprising and incredible history this research revealed.

A subantarctic diving petrel, 30 January 2018, Shoe Island, Auckland Islands. Photo by Alan Tennyson, Te Papa

The arcane art of taxonomy lies at the heart of natural history because it allows the world’s biodiversity to be documented in a globally consistent way. Taxonomy is the branch of science concerned with the classification of organisms. Every scientifically named organism was initially described in a publication.

However, often early descriptions were not as clear as they could have been. This is the case with Pelecanoides urinatrix exsul – the scientific name given to the subantarctic diving petrel in 1896 by the English naturalist Osbert Salvin (1835-1898).

Small chonky birds

Diving petrels are small birds that dive often and fly with whirring wings, like a giant bumble bee, across the surface of the wild southern oceans.

A subantarctic diving petrel, 21 January 2018, Ewing Island, Auckland Islands. Photo by Alan Tennyson, Te Papa

Many early scientific names that are still currently in use were given without clear reference to a particular specimen. Other names were bestowed on a series of specimens – this is what Salvin did when he published the scientific name of the subantarctic diving petrel; basing it on 23 different specimens.

The problem is that today we recognise that this series of 23 specimens includes three different kinds of diving petrel! So which of these specimens should his scientific name refer to?

One of the principles of the Code of Zoological Nomenclature is to try to maintain stability of names to minimise confusion. With this in mind, my co-authors and I set about examining the specimens that Salvin included in his original description. We were able to relocate almost all of them in the collection where Salvin described them – the Natural History Museum in England.

Now stored at Tring (Hertfordshire), this bird collection is among the largest and most comprehensive in the world and it contains many specimens of great historic interest. Our co-authors Joanne Cooper and Alex Bond work at Tring, so were invaluable on-the-spot experts who could check and double-check details of each specimen and their registration details.

Most of Salvins’ type series of *Pelecanoides urinatrix exsul* ready for examination. Photo by Alan Tennyson © Trustees of the Natural History Museum, London

The Erebus and Terror expedition

Our research into the specimens revealed a fascinating history. Several were collected by members of important historical UK expeditions: the 1939–1843 HMS Erebus and Terror Antarctic expedition, the 1872–1876 HMS Challenger oceanographic expedition, and the 1874–1875 Transit of Venus expedition.

Collectors of the petrels on the Erebus and Terror expedition included Robert McCormick who was an important early naturalist, having already accompanied Charles Darwin on the HMS Beagle.

*‘Erebus’ and the ‘Terror’ in New Zealand, August 1841*, by John Wilson Carmichael. Royal Museums Greenwich Public domain, via Wikimedia Commons

Another collector was famous polar explorer James Clark Ross.

Polar explorer and diving petrel collector James Clark Ross in 1834. Crop of *James Clark Ross* by John R. Wildman, (1785), National Maritime Museum. Public domain, via Wikimedia Commons

We deduced that James Clark Ross apparently collected this diving petrel at the Kerguelen Islands from the HMS Erebus in 1840.

Note the initials “JR” on the label. Photo by Alan Tennyson © Trustees of the Natural History Museum, London

Later, in 1848, Ross was sent on an unsuccessful search for Arctic explorer John Franklin’s expedition which disappeared in 1845. Franklin’s team had been searching for the Northwest Passage onboard the very vessels that Ross had commanded just a few years earlier – the Erebus and Terror. The remarkably intact sunken wrecks of the Erebus and Terror were finally only discovered in 2014 and 2016, respectively.

HMS *Erebus* was rediscovered, remarkably well-preserved on the Canadian seafloor in 2014; it had disappeared in 1845. Photo by Parks Canada

Divided into three

We concluded that the three different kinds of diving petrel included in Salvins’ series were: the common diving petrel (Pelecanoides u. urinatrix), the South Georgian diving petrel (Pelecanoides georgicus) and the subantarctic diving petrel.

In order to stabilise the names, we designated a primary type specimen that matched what is generally recognised as being the subantarctic diving petrel today. We selected this specimen because it is well-preserved and has detailed collection information (a female collected by Alfred Edward Eaton on 14 October 1874 in Observatory Bay, Royal Sound, Kerguelen Island, south Indian Ocean).

We designated this specimen as the primary type of Pelecanoides *urinatrix exsul.* Photo by Alan Tennyson © Trustees of the Natural History Museum, London

Our designation means that the name Pelecanoides urinatrix exsul can continue to be applied to birds that nest on islands in a circumpolar range around the southern oceans. This is one of the most common seabirds in Aotearoa New Zealand, with probably more than a million nesting on the subantarctic Antipodes Islands | Moutere Mahue, Auckland Islands | Maukahuka, and Campbell Island | Motu Ihupuku.

But this is only the beginning of the story. We now have a firm platform for future research that will review relationships between the different kinds of diving petrels. We have clarified one ambiguity but the taxonomy of this widespread group of birds still needs a detailed review.