Pycroft's Petrel Pterodroma pycrofti


Justification of Red List Category
This species is classified as Vulnerable because it has a very small range when breeding, being restricted to five tiny island groups, with the majority of the population on one island, and the introduction of invasive predator species could drive the species towards extinction within a very short time.

Population justification
The total breeding population is estimated at 5,000-10,000 pairs, equating to 12,000-22,000 mature individuals, within a total population of 30,000-40,000 individuals (G. Taylor in litt. 2012). There has been no population monitoring at any breeding colony (except the two translocation sites) since 2012 (G.Taylor in litt. 2016).

Trend justification
The population is increasing in response to rat eradication.

Distribution and population

Pterodroma pycrofti breeds under forest on 12 offshore islands along the east coast of New Zealand, in the Poor Knights Islands, the Hen and Chicken Islands, the Mercury Islands, and Ririwha (= Stephenson). Chick translocations to Cuvier Island in 2001-2003 have resulted in a small breeding population (numbering 14 pairs in 2012 and 20 pairs in 2015) (G. Taylor and Rob Chappell in litt. 2016). Studies utilising geolocators have shown that, when not breeding, birds disperse to the central and eastern tropical Pacific (G. Taylor in litt. 2012, Rayner et al. 2016). Subfossils indicate that the species once bred on Norfolk and Lord Howe Islands (to Australia) (Heather and Robertson 1997). Red Mercury Island (c.80% of total) supported 1,000-2,000 pairs in 1989-1991, and 2,000-3,000 in 1998. Surveys in 2010 indicate that this population has expanded to 5,000-10,000 pairs and is the dominant seabird on the island (G. Taylor in litt. 2012). The population at the Hen and Chicken Islands is probably less than 500 pairs. Other populations are tiny. The total breeding population is estimated at 5,000-10,000 pairs, with a total population of 30,000-40,000 birds (G. Taylor in litt. 2012). A translocation of Pycroft’s petrel chicks to Motuora Island started in March 2013 and two returned birds were seen ashore in December 2015 (J. Stewart pers.comm.). A banded adult found in May 2005 offshore Lelehudi Village, Milne Bay Province, Papua New Guinea, may indicate that some birds spend the non-breeding season in the Papua New Guinea region. The timing of the recovery does not rule out the possibility of a passing migrant (Pierce 2009).


It digs burrows on flat to steep coastal slopes below 150 m, often interspersed with other petrel colonies (Marchant and Higgins 1990, Heather and Robertson 1997). Adults return in Oct to clean out burrows, with egg-laying occurring in Nov-Dec, and young departing in Mar-Apr (Pierce 2009). Its diet is not well known, although it is known to take squid (Heather and Robertson 1997) and crustaceans (G. Taylor in litt. 2012).


A small minority nest on islands that still have Polynesian Rat (Rattus exulans), which has been shown to reduce Pycroft's Petrel reproductive success by predating on eggs and chicks (Pierce 2002).

Conservation actions

Conservation Actions Underway

Between 1987 and 1997, eradications of R. exulans were completed on Korapuki, Double, Stanley, Red Mercury, Lady Alice, Whatupuke and Coppermine Islands (Taylor 2000). As a result, breeding success has improved (as has that of P. assimilis [R. Pierce in litt. 1999]). Study populations have been established on Red Mercury and Stanley Islands. Populations on the Chicken Islands group were studied in the 1990s (Taylor 2000). Chick translocations to Cuvier Island in 2001-2003 have resulted in a small breeding population (G. Taylor in litt. 2012). Hen Island (500 ha) was cleared of R. exulans in 2011 (G. Taylor in litt. 2016). Pycroft’s Petrels were still present on Aorangi Island in 2013 but numbers seem very low (G.Taylor pers. comm. 2016). All breeding sites managed by the Department of Conservation of New Zealand get a biosecurity audit (using trained pest detection dogs) every 1-2 years (G. Taylor pers. comm.).

Conservation Actions Proposed

Survey Ririwha and Aorangi Islands to confirm breeding status and population size, and survey Fanal, Three Kings and Ohinau Islands for new colonies. Eradicate R. exulans from Ririwha Island if owners consent. Check all islands at least every five years to ensure that introduced predators have not established (Taylor 2000). 


26 cm. Small, grey-and-white petrel. White forehead merging into grey crown. Grey neck, back, uppertail-coverts, tail. Darker patch around eye. Darker grey wings showing M in flight. White underparts with indistinct grey half-collar. White underwing with dark tip, dark line along leading edge, extending indistinctly from carpal joint towards body. Similar spp. Separated from most other small gadfly petrels by whiter underwing. Stejneger's Petrel P. longirostris has more extensive, dark eye-patch. Cook's Petrel P. cookii generally appears lighter with lighter crown and eye patch. Pycroft's Petrel P. pycrofti may not be separable from Masatierra Petrel P. defilippiana, but ranges may not overlap.


Text account compilers
Stuart, A., Taylor, J., Anderson, O., Benstead, P., Fjagesund, T., Hermes, C., Martin, R., McClellan, R., Calvert, R., Moreno, R.

Taylor, G.A., Rayner, M., Miskelly, C., Pierce, R.

Recommended citation
BirdLife International (2021) Species factsheet: Pterodroma pycrofti. Downloaded from on 28/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from on 28/10/2021.