• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Taxonomic source(s)
Brooke, M. de L. 2004. Albatrosses and Petrels Across the World. Oxford University Press, Oxford.
Christidis, L. and Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. CSIRO Publishing, Collingwood, Australia.
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. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
SACC. 2005 and updates. A classification of the bird species of South America. Available at: https://www.museum.lsu.edu/~Remsen/SACCBaseline.htm.
Turbott, E.G. 1990. Checklist of the Birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	B2ab(iii)	B2ab(iii); D2

Red List history

Year	Category	Criteria
2018	Endangered	B2ab(iii)
2017	Endangered	B2ab(iii)
2016	Vulnerable	D2
2012	Vulnerable	D2
2010	Vulnerable	D2
2008	Vulnerable	D2
2005	Vulnerable
2004	Vulnerable
2000	Vulnerable
1996	Vulnerable
1994	Vulnerable
1988	Threatened

Migratory status	full migrant	Forest dependency	high
Land-mass type		Average mass	-

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	30,600,000 km2	medium
Area of Occupancy (breeding/resident)	16 km2	medium
Number of locations	2-5	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	7900-13700 mature individuals	good	estimated	2005
Population trend	unknown	medium	-	-
Generation length	30.2 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: The most recent estimate of population size is 2,954-5,137 annual breeding pairs (Wood and Otley 2013), but given that not all individuals breed each year this is likely to be an underestimate for the number of mature individuals. Assuming that 25% of breeding age birds may skip breeding in any one year (as derived from long-term data sets on similar species) (B. Baker in litt. 2012), the population size is estimated at 7,877-13,698 mature individuals, rounded here to 7,900-13,700 mature individuals.

Following the tropical storm Ita in 2014, there was considerable damage to the breeding area, with the loss or damage of up to 50% of the major colonies, which contain up to 75% of the breeding population (Waugh et al. 2015b). Fortunately, the storm occurred before the laying period and so adults may not have been killed in their nests, unless they were visiting prior to breeding (which some birds have been reported to do) (S. Waugh in litt. 2016), and some birds have moved between impacted colonies (S. Waugh in litt. 2016). Therefore, the level of destruction may not equate to any decline in population, and no population data subsequent to the storm are yet available, though surveys are currently underway (S. Waugh in litt. 2016).

Trend justification: The population was estimated to slowly increase at a rate of 1.8% per year between 1970 and 2012 (Waugh et al. 2015a). However, earlier counts are considered unreliable (S. Waugh in litt. 2017) so the population trend is uncertain.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Argentina	extant	vagrant
Australia	extant	vagrant			yes
Chile	extant	native			yes
New Zealand	extant	native		yes

Country/Territory	IBA Name
New Zealand	Punakaiki
New Zealand	West Coast South Island (North) (offshore)

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Temperate	major	breeding
Marine Neritic	Pelagic	major	non-breeding
Marine Neritic	Pelagic	major	breeding
Marine Oceanic	Epipelagic (0-200m)	major	non-breeding
Marine Oceanic	Epipelagic (0-200m)	major	breeding
Altitude		Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Livestock farming & ranching - Agro-industry grazing, ranching or farming	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Majority (50-90%)		Slow, Significant Declines		Past Impact
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Fishing & harvesting aquatic resources - Unintentional effects: (large scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Biological resource use	Fishing & harvesting aquatic resources - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Unknown		Unknown
		Stresses Species mortality
Biological resource use	Hunting & trapping terrestrial animals - Intentional use (species is the target)	Timing		Scope		Severity		Impact
		Unknown		Minority (<50%)		Negligible declines		Unknown
		Stresses Species mortality
Climate change & severe weather	Storms & flooding	Timing		Scope		Severity		Impact
		Past, Likely to Return		Majority (50-90%)		Causing/Could cause fluctuations		Past Impact
		Stresses Ecosystem degradation, Reduced reproductive success, Species mortality
Geological events	Avalanches/landslides	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Canis familiaris	Timing		Scope		Severity		Impact
		Past, Likely to Return		Minority (<50%)		Causing/Could cause fluctuations		Past Impact
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Felis catus	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		No decline		Low Impact: 5
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Sus domesticus	Timing		Scope		Severity		Impact
		Future		Majority (50-90%)		Rapid Declines		Low Impact: 5
		Stresses Ecosystem degradation, Species mortality
Pollution	Excess energy - Light pollution	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Unknown		Unknown
		Stresses Reduced reproductive success, Species mortality

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Recommended citation
BirdLife International (2024) Species factsheet: Westland Petrel Procellaria westlandica. Downloaded from https://datazone.birdlife.org/species/factsheet/westland-petrel-procellaria-westlandica on 23/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 23/12/2024.