Pterodroma axillaris 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Procellariiformes Procellariidae

Scientific Name: Pterodroma axillaris
Species Authority: (Salvin, 1893)
Common Name(s):
English Chatham Petrel, Chatham Islands Petrel, Chatham Island Petrel
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Lynx Edicions BirdLife International.
Identification information: 30 cm. Small, grey-and-white gadfly petrel with unique underwing pattern. Dark grey crown, sides of face and neck. Black mark behind eye. Grey upperparts. Grey tail with dark tip. Grey upperwing with dark, moderately distinct "M". Pale grey half-collar at sides of breast. Rest of underparts white. White underwing with dark tip, broad, black bar extending from axillaries (where broadest) to carpal joint, then less prominently towards tip. Similar spp. Black underwing bar of Black-winged Petrel P. nigripennis does not reach body and axillaries. Larger Mottled Petrel P. inexpectata has bold bar, but has dark centre to belly. Voice Flight call whis-whis-whis, oi, purring call given on ground.

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2be+4be; D2 ver 3.1
Year Published: 2015
Date Assessed: 2015-10-01
Assessor(s): BirdLife International
Reviewer(s): Symes, A.
Contributor(s): Hitchmough, R., Scofield, P., Taylor, G.A., Tennyson, A., Wilson, K. & Bourne, W.
Facilitator/Compiler(s): Anderson, O., Benstead, P., Bird, J., Calvert, R., Lascelles, B., McClellan, R., Taylor, J., Temple, H. & Ashpole, J
This species has been downlisted to Vulnerable because although its population has undergone a rapid decline over the past three generations and it is restricted to just three locations, the population has been increasing since 2000 owing to intensive conservation action including two translocations, such that the decline over the past three generations has no longer been very rapid.

Previously published Red List assessments:
2013 Endangered (EN)
2012 Endangered (EN)
2010 Endangered (EN)
2009 Endangered (EN)
2008 Critically Endangered (CR)
2007 Critically Endangered (CR)
2006 Critically Endangered (CR)
2004 Critically Endangered (CR)
2000 Critically Endangered (CR)
1996 Critically Endangered (CR)
1994 Critically Endangered (CR)
1988 Threatened (T)

Geographic Range [top]

Range Description: This species is restricted to South East Island (= Rangatira) and Pitt Island and Main Chatham Island in the Chatham Islands, New Zealand, having been reintroduced to both of the latter two (J. Hobbs in litt. 2009). Subfossils indicate that it was once more widespread, being present on Mangere Islands (A. J. D. Tennyson per P. Scofield in litt. 2012). The earliest estimate of 50 birds was later revised to 200-400 (Marchant and Higgins 1990). A mark-recapture census in 2004 estimated that the global population stood at 1,000-1,100 individuals comprising 250 breeding pairs, a floater population of adults unable to breed each year owing to loss of partners or nesting sites, and juveniles aged up to five years (Taylor 2000, G. Taylor in litt. 2009). The increase reflects an improvement in knowledge and since 2000, a marked response to successful management with over 100 chicks now fledging annually and many recruiting back to the island.

Significant declines occurred during the 20th century and continued into the 1990s; an annual decline of 1% per annum has been crudely estimated and cautious interpretation suggests a gross decline of 40-50% or more may have occurred over the past three generations (G. Taylor in litt. 2009). Trends appear to have stabilised since 2000, prompted by successful conservation measures. Between 2002 and 2006, 200 chicks were moved to a newly created predator-free site on Pitt Island; successful breeding first occurred in 2006 (Anon 2006), and 17 pairs were present in 2012 (G. Taylor in litt. 2012). About 200 chicks were transferred to the 7.5-ha Sweetwater Conservation Covenant on the main Chatham Island between 2008 and 2011. The first breeding attempt at this site occurred in 2012 (G. Taylor in litt. 2012, Bell et al. 2013). It migrates to the northern Pacific Ocean like the closely-related P. nigripennis, and has been recorded at sea to the south of the islands (Heather and Robertson 1997, R. Hitchmough in litt. 2005). Tracking research conducted in 2009/2010 using geolocators has shown that birds feed mainly south and east of the Chatham Islands during the breeding season, with the Bollons Seamount being important during chick rearing (Rayner et al. 2012), and migrate to the eastern Pacific in winter to an area over and north of the Nazca sea ridge, about 1,000-1,500 km west of Chile and Peru (G. Taylor in litt. 2012).

Countries occurrence:
New Zealand
Estimated area of occupancy (AOO) - km2: 2
Continuing decline in area of occupancy (AOO): Unknown
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2: 1710000
Continuing decline in extent of occurrence (EOO): Unknown
Extreme fluctuations in extent of occurrence (EOO): No
Number of Locations: 3
Continuing decline in number of locations: Unknown
Extreme fluctuations in the number of locations: No
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Based on an age at first breeding of three years, and an estimate that at least 75% of birds will be over three years old, the latest total population estimate from 2010 of c. 1,400 individuals probably includes c. 1,100 mature individuals (G. Taylor in litt. 2012).

Trend Justification:  Occupied burrows and the number of surface birds declined at areas in common usage in the 1930s, into the 1990s. Intense, sometimes lethal, competition with Broad-billed Prions Pachyptila vittata for burrow space precipitated recent declines, crudely estimated at 1% per annum equating to approximately 50% over the past three generations. Since 1997, however, control of prions at known petrel burrows, a practice replaced by use of burrow flaps since 2001, has greatly improved nesting success and the population is now increasing; a trend boosted by two recent and successful translocations to predator free conservation covenants on Pitt Island and Chatham Island. The total population has now recovered from 600-800 birds in 1995 to about 1,400 birds in 2010 (based on mark-recapture and burrow survey analysis) (G. Taylor in litt. 2012). The population continues to increase and birds have been colonising formerly occupied parts of South East Island (G. Taylor in litt. 2012, K.J. Wilson in litt. 2012). Although dependent on conservation action, the continued population increase makes it likely that the population size reduction over the past three generations (47 years) is now less than 50% (G. Taylor in litt. 2012). However the reduction is still likely to be greater than 30%.

Current Population Trend: Increasing
Additional data:
Number of mature individuals: 1100 Continuing decline of mature individuals: No
Extreme fluctuations: No Population severely fragmented: No
No. of subpopulations: 1 Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: No All individuals in one subpopulation: Yes
No. of individuals in largest subpopulation: 100

Habitat and Ecology [top]

Habitat and Ecology: It nests in burrows in very friable densely burrowed soils in lowland temperate forest and scrub, on flat to moderate sloping ground (Marchant and Higgins 1990). Its diet is not well known but includes squid and small fish. Some young have returned to the island at two years old (Heather and Robertson 1997), and breeding has been recorded at the age of three, although most individuals do not breed until five years of age (G. Taylor in litt. 2009). Much of the life cycle is spent at sea; birds return to land only to breed. Visits to the colony occur after dark.

Systems: Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat: Unknown
Generation Length (years): 15.6
Movement patterns: Full Migrant
Congregatory: Congregatory (and dispersive)

Threats [top]

Major Threat(s): On South East Island, intense competition for burrows with the abundant Broad-billed Prion Pachyptila vittata (including lethal attacks on chicks and eggs, and occasionally adults) is the primary threat (Was et al. 2000). Such competition may be the cause of the observed low breeding success and high rate of pair-bond disruption. On the other islands in the group, exploitation by humans for food and introduced predators were the probable causes of extirpation (Taylor 2000). Predator-proof fencing has facilitated translocations to two Conservation Covenants on Pitt Island and Chatham Island; alien invasive mammals will remain a constant potential threat to these sites and on-going management will be required.

Conservation Actions [top]

Conservation Actions: Conservation and Research Actions Underway
South East Island has been managed as a reserve since 1954, and cattle, sheep and goats were removed in 1961 (Marchant and Higgins 1990, Taylor 2000). Intensive research, on-going since 1991, helped to identify the impact of Pachyptila vittata. As a consequence, artificial nest-sites have been provided and burrows have been blocked to prevent occupation by P. vittata during the absence of Pterodroma axillaris. P. vittata found occupying P. axillaris burrows are culled (Taylor 2000). Since 2001, neoprene burrow flaps installed at burrow entrances have greatly reduced prion impacts during the period February to April (Sullivan and Wilson 2001). These measures have greatly improved breeding success (G. Taylor in litt. 1999, Taylor 2000), from 10-30% in early 1990s to a mean of 80% in 2000-2010 (Gummer et al. 2015). Intensive burrow searches have now located over 160 active breeding sites of the estimated 250 pairs using the island. All newly located burrows are converted to artificial nest sites and are safe-guarded from prion interference. The project aims to maximise productivity from the approximately 150 mapped and managed burrows (G. Taylor in litt. 2015).

In 2002, a second population was created in a predator free enclosure on the 40-ha Ellen Elizabeth Preece Conservation Covenant (EEPCC). Over a period of four years, 200 chicks were transferred to this site, and by 2006 four birds had returned with a pair successfully rearing a single chick for the first time (Taylor 2000, Anon 2006). In 2006-2007, four pairs nested and four chicks were reared. This included one pair of unbanded birds that have been lured presumably to the site by the sound attraction system. In 2008, seven chicks fledged from the EEPCC. About 200 chicks were transferred to the 7.5-ha Sweetwater Conservation Covenant on the main Chatham Island between 2008 and 2011. In the 2011-2012 breeding season, a pair successfully raised a chick in the Sweetwater Conservation Covenant, and several more burrows were active (per P. Scofield in litt. 2012, G. Taylor in litt. 2012). In 2009-2010, 22 geolocation tags were applied to breeding Chatham petrels and 18 were recovered (Rayner et al. 2012).

and Research Actions ProposedMonitor breeding burrows annually and mark all chicks. Continue to protect nesting birds. Continue translocating birds to the Sweetwater Conservation Covenant on Chatham Island until a self-maintaining population is established. Use tiny geolocation tags to investigate the species's at-sea distribution across multiple years, and identify potential threats.

Citation: BirdLife International. 2015. Pterodroma axillaris. The IUCN Red List of Threatened Species 2015: e.T22697949A84014341. . Downloaded on 30 November 2015.
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