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

Taxonomic note
P. auricularis (del Hoyo and Collar 2014) is retained as a separate species from P. newelli (which see) (Handbook of the Birds of the World and BirdLife International 2018), following a revision of the scoring of parsed characters for these taxa plus P. myrtae (Handbook of the Birds of the World and BirdLife International 2018), split from P. newelli (del Hoyo and Collar 2014).

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. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Handbook of the Birds of the World and BirdLife International. 2018. Handbook of the Birds of the World and BirdLife International digital checklist of the birds of the world. Version 3. Available at: https://datazone.birdlife.org/userfiles/file/Species/Taxonomy/HBW-BirdLife_Checklist_v3_Nov18.zip.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
B2ab(i,ii,iii,v)	B2ab(i,ii,iii,v)	A2bce+3bce; B2ab(i,ii,iii,v); D1

Red List history

Year	Category	Criteria
2018	Critically Endangered	B2ab(i,ii,iii,v)
2016	Critically Endangered	B2ab(i,ii,iii,v)
2015	Critically Endangered	B2ab(i,ii,iii,v)
2013	Critically Endangered	B2ab(i,ii,iii,v)
2012	Critically Endangered	B2ab(i,ii,iii,v)
2010	Critically Endangered	B2a+b(i,ii,iii,v)
2009	Critically Endangered	B2a+b(i,ii,iii,v)
2008	Critically Endangered
2007	Critically Endangered
2006	Critically Endangered
2004	Critically Endangered
2000	Critically Endangered
1996	Vulnerable
1994	Vulnerable
1988	Threatened

Migratory status	full migrant	Forest dependency	does not normally occur in forest
Land-mass type		Average mass	323 g

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	3,200,000 km2	medium
Area of Occupancy (breeding/resident)	9 km2	medium
Number of locations	1	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	250-999 mature individuals	medium	estimated	2008
Population trend	decreasing	poor	inferred	1956-2010
Rate of change over the past 10 years/3 generations (longer of the two periods)	30-49%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	30-49%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	30-49%	-	-	-
Generation length	18 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: Surveys in 2008 found fewer than 100 breeding pairs on Socorro, suggesting that even accounting for non-breeding birds the total global population may be as low as 250-999 mature individuals, and that previous at sea estimates (which were subject to a high degree of error) may have been too large (J. Martínez-Gomez in litt. 2008). This estimate equates to 375-1,499 individuals in total, rounded here to 350-1,500 individuals.

Trend justification: A rapid population decline over the last three generations is estimated from surveys carried out since 1980, but exact trends are difficult to determine owing to inconsistencies between estimates of the breeding population and total numbers at sea (Brooke 2004). A noticeable reduction in nesting colonies has occurred since the observations of Martínez-Gómez and Jacobsen (2004, J. Martínez-Gómez in litt. 2012). 

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
French Southern Territories	extant	vagrant
Guam (to USA)	extant	vagrant			yes
Mexico	extant	native	yes	yes
Northern Mariana Islands (to USA)	extant	vagrant			yes
Panama	extant	vagrant			yes
United States Minor Outlying Islands (to USA)	extant	vagrant			yes

Country/Territory	IBA Name
Mexico	Islas Revillagigedo

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Marine Neritic	Macroalgal/Kelp	suitable	non-breeding
Marine Neritic	Macroalgal/Kelp	suitable	breeding
Marine Neritic	Pelagic	major	non-breeding
Marine Neritic	Pelagic	major	breeding
Marine Neritic	Seagrass (Submerged)	suitable	non-breeding
Marine Neritic	Seagrass (Submerged)	suitable	breeding
Marine Neritic	Subtidal Loose Rock/pebble/gravel	suitable	non-breeding
Marine Neritic	Subtidal Loose Rock/pebble/gravel	suitable	breeding
Marine Neritic	Subtidal Rock and Rocky Reefs	suitable	non-breeding
Marine Neritic	Subtidal Rock and Rocky Reefs	suitable	breeding
Marine Neritic	Subtidal Sandy	suitable	non-breeding
Marine Neritic	Subtidal Sandy	suitable	breeding
Marine Neritic	Subtidal Sandy-Mud	suitable	non-breeding
Marine Neritic	Subtidal Sandy-Mud	suitable	breeding
Marine Oceanic	Epipelagic (0-200m)	major	non-breeding
Marine Oceanic	Epipelagic (0-200m)	major	breeding
Marine Oceanic	Mesopelagic (200-1000m)	major	non-breeding
Marine Oceanic	Mesopelagic (200-1000m)	major	breeding
Shrubland	Subtropical/Tropical High Altitude	major	breeding
Altitude	0 - 900 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Climate change & severe weather	Habitat shifting & alteration	Timing		Scope		Severity		Impact
		Future		Whole (>90%)		Unknown		Unknown
		Stresses Indirect ecosystem effects, Ecosystem degradation
Geological events	Volcanoes	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Minority (<50%)		Very Rapid Declines		Past Impact
		Stresses Ecosystem degradation, Ecosystem conversion, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Capra hircus	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Minority (<50%)		Slow, Significant Declines		Past Impact
		Stresses Ecosystem degradation
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Felis catus	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Rapid Declines		High Impact: 8
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Mus musculus	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Slow, Significant Declines		Medium Impact: 7
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Named species	Timing		Scope		Severity		Impact
		Future		Whole (>90%)		Rapid Declines		Medium Impact: 6
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Oryctolagus cuniculus	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Slow, Significant Declines		Medium Impact: 7
		Stresses Ecosystem degradation
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Ovis aries	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Minority (<50%)		Slow, Significant Declines		Past Impact
		Stresses Ecosystem degradation
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Sus domesticus	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Minority (<50%)		Very Rapid Declines		Past Impact
		Stresses Ecosystem degradation, Species mortality
Pollution	Excess energy - Light pollution	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species mortality

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Recommended citation
BirdLife International (2024) Species factsheet: Townsend's Shearwater Puffinus auricularis. Downloaded from https://datazone.birdlife.org/species/factsheet/townsends-shearwater-puffinus-auricularis on 22/12/2024.
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 22/12/2024.