In search of the New Zealand Storm Petrel (Pealeornis maoriana)
The New Zealand storm petrel was described from three specimens: No.18126.96.36.199 (British Natural History Museum, Tring), which G.M. Mathews designated as the type of Pealeornis maoriana (Mathews 1932), collected by Steet in or just before 1895 "off Banks Peninsula, New Zealand" (Mathews 1932; Medway 2004; but see Bourne & Jouanin 2004); and two (Nos. 17 = 14393 and 18 = 14372 in Museum National d'Histoire Naturelle, Paris) collected off East Cape, North Island during the first cruise of the French corvette Astrolabe on 8 February 1827 (Quoy & Gaimard 1830; Bourne & Jouanin 2004; Medway 2004). Mathews' (1932) designation was disputed by Murphy & Snyder (1952) who concluded the specimens to be a pale morph (the "Pealea" phenomenon) of Wilson's storm petrel (Oceanites oceanicus) because they were considered similar in size and proportions, although differing in having longer tarsi and streaked underparts (Bourne & Jouanin 2004). Oliver (1955) disagreed and, while accepting Murphy & Snyder's generic disposition, treated the specimens as a separate species O. maorianus.
Subsequently the New Zealand storm petrel slid into obscurity, with no further records for over 100 years, although evidence for a former population in New Zealand surfaced when sub-fossil bones from two sites (Wheturau Quarry, eastern North Island and Te Ana Titi, South Island West Coast) were identified as most likely being of this taxon (Worthy 2000). Then on 25 January 2003 the sighting of a single black and white storm petrel off Coromandel Peninsula by Saville and Stephenson turned the spotlight on the species. Initially they identified the bird as a black-bellied storm petrel (Fregetta tropica), but subsequently suggested it might be the New Zealand storm petrel (Saville et al. 2003). This attention intensified when, on 17 November 2003, two British birdwatching enthusiasts B. Flood and B. Thomas (Flood 2003) observed, photographed and video-taped at least 10 similar storm petrels north of Little Barrier Island. They claimed these to be New Zealand storm petrel (Flood 2003), a claim subsequently not accepted by the Ornithological Society of New Zealand's Rare Birds Committee (Rare Birds Committee 2005). Their sighting followed a tantalising glimpse in rough weather of a small, black and white storm petrel two weeks previously in much the same area (C. Gaskin pers. obs.), during a pelagic bird-watching trip led by us.
Many sightings of these storm petrels have since followed and our study (to be published in the forthcoming December 2005 issue of NOTORNIS, the OSNZ journal) details our search for these birds. Observations have been made to attempt to establish their distribution and identity, and to gain insights into their biology. We observed black and white storm petrels on 31 seabird-watching trips to the outer Hauraki Gulf, New Zealand, November 2003 - November 2005. We studied their characteristics, behaviour and seasonal occurrence: the sightings were concentrated in the outer Hauraki Gulf from October to March and further offshore in April-May.
All sightings of New Zealand storm petrels in the Hauraki Gulf since 1 November 2003 have been plotted against trip routes, wind direction and strength, chumming locations and non-sightings while chumming. This data will be presented in full in our NOTORNIS paper. Seasonal behaviour and known breeding sites of White-faced storm petrel (Pelagodroma marina) are additional factors in this study. Further analysis of sightings will be carried out jointly with Department of Conservation and other interested parties to advance the search for New Zealand Storm Petrel breeding areas. This summer, (2005/2006) we have seen New Zealand storm petrels on all our pelagics since 9 October (29 October, 4, 5 & 14 November).
With the capture of the bird on board Geordie Murman’s boat off Little Barrier on 4 November, Richard Griffiths (DOC) and Karen (Baird) were able to process it, taking measurements and photos and confirming it to be one of the black and white storm petrels we'd been seeing in the Hauraki Gulf since November 2003 during summer months. The bird was also banded with an aluminium band on the right leg tarsus. Feathers were taken for DNA analysis, along with a feather louse. The bird was later released, and flew off strongly.
In light of the material now at hand we now regard these birds as the New Zealand storm petrel Pealeornis maoriana. However formal taxonomic identification has yet to be completed, likewise ratification by the NZ Rare Birds Committee (Nov 05).
Why the resurgence of New Zealand storm petrels?
Why the hiatus in observations or identifications of this species from c.1890 to 2003? Possible reasons include: (1) New Zealand storm petrels were seen but identified as something else e.g., identifications were made based on known extant species, or white on the belly not being seen because of poor ventral views or deep shadow cast across the underparts; (2) relatively few expert bird observers were on the many boats that ply Hauraki Gulf waters every summer; (3) relatively few boats visit the outer Hauraki Gulf; (4) dedicated seabird-viewing trips with groups of people actively looking for seabirds is a recent phenomenon; (5) small storm petrels are hard to see while cruising in conditions other than light breezes with calm to little sea, unless they are within 30-50 m of the boat; (6) chumming as a technique to attract seabirds close to boats was not used in the Hauraki Gulf prior to November 2003; (7) greater use of photography (especially digital photography) has permitted identification of these birds; and (8) New Zealand storm petrels may represent a formerly near-extinct species, which has been released from predation pressure and has now increased to the point where it is more easily detectable.
The Mokohinau Islands, comprising four islands and 12 islets/stacks, are at the heart of the sightings distribution, they are attractive to small breeding seabirds because of their generally shallow soils and their proximity to the edge of the continental shelf, they include a few stacks and islets that have always been rat-free, Today the Mokohinau Islands offer excellent, rat-free breeding habitat for a small storm petrel, whether burrowing, amongst dense vegetation or in rock crevices. The spread of white-faced storm petrels to Burgess Island (formerly heavily-grazed, rat-infested and inhabited) from Lizard Islet (where they remain), and perhaps elsewhere, within 15 years illustrates this dramatically.