What isn’t as well-known is that for over a hundred years the bird has been classified as a sub-species of the wide ranging great-winged petrel.

But in a study just published in the Zoological Journal of the Linnean Society, scientists from Landcare Research, Canterbury Museum, Department of Conservation and the University of Canberra analysed the mitochondrial DNA, morphology, biology and behaviour of the grey-faced petrel, revealing it to be highly distinct from the great-winged petrel, and all other petrel species.

“In fact, our results indicate that the lineage giving rise to the grey-faced petrel diverged from other petrels several million years ago, meaning it is actually a species quite unique to New Zealand”, lead-author Jamie Wood of Landcare Research said, “and, surprisingly, it turns out that the grey-faced petrel isn’t even the closest relative of the great-winged petrel after all”.

Paul Scofield of Canterbury Museum, and a co-author of the study, said “the grey-faced petrel looks superficially similar to the great-winged petrel, and this is where the confusion arose. However, our study shows that they differed greatly in their genetics, skeletal features and vocalisations; the latter being a key feature that separates petrel species”.

Raising the grey-faced petrel to full species status increases the degree of New Zealand’s seabird endemism to 43 per cent, the highest rate for any country, and emphasises the importance of the New Zealand region as a hotspot for seabird diversity. While the grey-faced petrel appears secure (with an estimated 200,000 to 300,000 breeding pairs on the major breeding islands around New Zealand), the findings may have conservation implications for the great-winged petrel, whose population is now much smaller than previously realised. Colonies of great-winged petrel on subantarctic islands are at risk from introduced species such as mice, rats and feral cats. The threat status of these populations will likely be raised as a result of this split.

Co-author Phil Lyver from Landcare Research, acknowledged that “the grey-faced petrel and its harvest is hugely significant for many coastal iwi around the North Island. Our findings, alongside results from a related study that demonstrated grey-faced petrels were of a single genetic population, will inform kaitiakitanga and conservation responses that promote the growth and restoration of colonies both on offshore islands and the mainland.”

Reference: Jamie R Wood, Hayley A Lawrence, R Paul Scofield, Graeme A Taylor, Phil O’B Lyver, Dianne M Gleeson (2016) Morphological, behavioural and genetic evidence supports reinstatement of full-species status for grey-faced petrel, Pterodroma macroptera gouldi (Procellariiformes: Procellariidae). Zoological Journal of the Linnean Society. doi: 10.1111/zoj.12432