The deep-billed petrel lived in the Pliocene epoch, about 3 million years ago. It is known from fossil remains from the South Taranaki coast found by amateur collector John Buchanan-Brown, from New Plymouth. John found the remains in 2015 encased in solid rock, and then meticulously prepared out the delicate bones.

When the bird died, it must have sunk to the bottom of a gentle sea and got buried in the fine sediment, which protected it as it fossilised. Due to tectonic activity, the old sea-floor was pushed up and eventually coastal erosion revealed the fossil again.

The holotype and only known specimen (NMNZ S.46691) is held at the Museum of New Zealand Te Papa Tongarewa in Wellington. It is remarkably well-preserved and includes many parts of the skeleton: a partial skull (including the beak), the furcula, right scapula, both coracoids, the right humerus, both ulnae, the right radius, the synsacrum, the left  femur, both tibiotarsi, both tarsometatarsi and one toe.

The deep-billed petrel was a close relative of the largest known members of the genus Procellaria, such as the white-chinned petrel (P. aequinoctialis) and Westland petrel (P. westlandica). Compared with these species, it had a deeper and shorter bill (reflected in the scientific name altirostris, meaning ‘deep bill’), a larger coracoid and shorter wings, while its legs were a similar size. It would have been slightly larger than the grey petrel (P. cinerea) and notably larger than the black petrel (P. parkinsoni). The grey petrel also differs from other members of the genus by having a more slender beak.

Like its relatives, the deep-billed petrel presumably nested in burrows and laid a single large white egg, raising no more than one chick a year. It would have foraged at sea using surface feeding and shallow dives, probably eating a mixture of fish, cephalopods and crustaceans, but often scavenging. Compared with its closest relatives, its relatively short wings, particularly the short ulna compared with the humerus length, suggest that it may have been more of a diver when feeding, and it may have used gliding flight less. All members of the genus travel thousands of kilometres at sea as part of their normal lives, and so the deep-billed petrel presumably had similar behaviours, ranging widely around proto–New Zealand and probably also undertaking long-distance migrations.

While New Zealand today is the global centre of diversity for species of petrels, including species of Procellaria, with four breeding species, the deep-billed petrel is the only evidence of this genus being present in the country prior to the last few thousand years. It demonstrates a long history for the genus in the region.

Globally Procellaria fossils are extremely rare. Apart from the Taranaki fossil, there are only two other reports of fossils of the genus – both are in slightly older deposits and both are far less complete remains: a single partial humerus from the early Pliocene of South Africa, and three bones from the early Pliocene of North Carolina, U.S.A. The lack of a good fossil record for the genus impairs a more detailed understanding of its evolution.

The deep-billed petrel is the fourth species of fossil seabird named from the Pliocene rocks of South Taranaki; the others being: Pom’s shearwater (Ardenna davealleni), Alastair’s albatross (Aldiomedes angustirostris) and the dawn crested penguin (Eudyptes atatu).

Weblinks

Taranaki Daily News

Wikipedia

References

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

Olson, S.L.; Rasmussen, P.C. 2001. Miocene and Pliocene birds from the Lee Creek Mine, North Carolina. In:  Ray, C.R. & Bohaska, D.J. (Eds.). Geology and  paleontology  of  the  Lee  Creek  Mine,  North  Carolina,  III. Washington, D.C., Smithsonian Institution Press. p. 233‑365.

Tennyson, A.J.D.; Tomotani, B.M. 2021. A new fossil species of Procellaria (Aves: Procellariiformes) from the Pliocene of New Zealand. Papéis Avulsos de Zoologia 61: e20216116.

Recommended citation

Tennyson, A.J.D. 2022. Deep-billed petrel. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz