Pom’s shearwater was discovered in 3 million year old Pliocene rocks on the South Taranaki coast. It is known from two well-preserved partial specimens.

Dave Allen collected the fossil that became the holotype (NMNZ S.45183) of the species in 2006. A second specimen (NMNZ S.46316) was found in 2011 by Xavier Johnson and this became the paratype of the species. Both specimens are held by the Museum of New Zealand Te Papa Tongarewa, Wellington. The holotype preserves 14 recognisable elements, including the humeri, ulnae, radii, carpometacarpi, femora and tarsometatarsi. The paratype includes the humeri, ulnae, radii, carpometacarpi, plus the tibiotarsus, fibula and tarsometatarsus from the right leg. Both specimens lack the skull and all the pectoral and pelvic elements. At his request, the common name for the species - Pom’s shearwater - honours Dave ‘Pom’ Allen.

Pom’s shearwater is distinguished from all known extant and extinct shearwaters by a unique combination of skeletal features. It was as large as the largest species of shearwater – the great shearwater – which weighs 605–1060 g. However it was structurally most similar to the more delicate Buller’s shearwater, which weighs 385–490 g. Its wing bones were similar to those found in large gliding shearwaters, such as Buller’s, wedge-tailed, flesh-footed, pinked-footed, and great shearwaters. Smaller diving shearwater species and the sooty and short-tailed shearwater have differently proportioned wings and flattened humeri, because they use their wings as paddles under water. Therefore Pom’s shearwater is thought to have been more of a gliding species than a diving bird.

It probably foraged using surface feeding and shallow dives, eating a mixture of fish, cephalopods and crustaceans. All shearwaters travel thousands of kilometres at sea as part of their normal lives, so Pom’s shearwater presumably had similar behaviours, ranging widely around proto–New Zealand and probably also undertaking long-distance migrations.

Pom’s shearwater would have been like all its relatives, laying a single white egg and raising no more than one chick each year.

Many fossil species of shearwater have been named. These are from widely distributed locations but mainly from Miocene and Pliocene North Atlantic and North Pacific coastal deposits. Shearwater fossils are surprisingly rare in the southern hemisphere, consisting of a range of modern or unidentified taxa from South Africa and the western South American coast.

Pom’s shearwater represents the first pre-Pleistocene (> 2.5 milllion year old) record of a shearwater taxon from the western Pacific and helps reveal the history of shearwater evolution. A similarly-aged shearwater skull from a smaller species from near Taihape has been reported, but its affinities remain unclear. In fact, the fossil record of all Procellariiformes in the western Pacific is minimal.

Today, New Zealand has the greatest diversity of breeding shearwater species in the world, with nine species. The new fossil adds weight to other evidence that shearwaters have a long history in this region.

Pom’s shearwater was the first of four species of fossil seabird named from the Pliocene rocks of South Taranaki; the others being: Alastair’s albatross (Aldiomedes angustirostris), the dawn crested penguin (Eudyptes atatu) and the deep-billed petrel (Procellaria altirostris).

References

Chandler, R.M. 1990. Recent advances in the study of Neogene fossil birds. Part II. Fossil birds of the San Diego Formation, Late Pliocene, Blancan, San Diego County, California. Ornithological Monographs 44: 73–161.

Henderson, N.; Gill, B.J. 2010. A mid-Pliocene shearwater skull (Aves: Procellariidae: Puffinus) from the Taihape Mudstone, central North Island, New Zealand. New Zealand Journal of Geology and Geophysics 53: 327–332.

Hoffmeister, M.C., Carrillo, J.D.; Nielsen, S.N. 2014. The evolution of seabirds in the Humboldt Current: new clues from the Pliocene of central Chile. PloS ONE 9(3): e90043.

Howard, H. 1949. New avian records for the Pliocene of California. Carnegie Institution of Washington Publication 584: 179–199.

Howard, H. 1971. Pliocene avian remains from Baja California. Natural History Museum of Los Angeles County Contributions in Science 217: 1-17.

Olson, S.L. 1985. Early Pliocene Procellariiformes (Aves) from Langebaanweg, South-Western Cape Province, South Africa. Annals of the South African Museum 95: 123–145.

Olson, S.L. 1985. An Early Pliocene marine avifauna from Duinefontein, Cape Province, South Africa. Annals of the South African Museum 95: 147–164.

Tennyson, A.J.D.; Mannering, A.A. 2018. A new species of Pliocene shearwater (Aves: Procellariidae) from New Zealand. Tuhinga: Records of the Museum of New Zealand Te Papa Tongarewa 29: 1-19.

Warheit, K.I. 2002. The seabird fossil record and the role of paleontology in understanding seabird community structure. Pp. 17–55 in Schreiber, E.A. and Burger, J. (eds). Biology of marine birds. CRC Press, Boca Raton, Florida, U.S.A.

Recommended citation

Tennyson, A.J.D. 2022. Pom’s shearwater. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz