• 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.
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.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	-	-

Red List history

Year	Category	Criteria
2022	Near Threatened	A2cde; B2b(ii,iii)
2016	Near Threatened	A2ce; B2ab(i,ii,iii,v)
2012	Near Threatened	A2ce;B2ab(i,ii,iii,v)
2010	Near Threatened	A2c,e; B2a+b(i,ii,iii,v)
2008	Near Threatened	A2c,e; B2a+b(i,ii,iii,v)
2005	Near Threatened
2004	Near Threatened
2000	Vulnerable
1996	Vulnerable
1994	Vulnerable
1988	Near Threatened

Migratory status	full migrant	Forest dependency	does not normally occur in forest
Land-mass type	shelf island	Average mass	408 g

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	38,400 km2	medium
Extent of Occurrence (non-breeding)	2,500,000 km2	medium
Area of Occupancy (breeding/resident)	504 km2	medium
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	200000-299999 mature individuals	medium	estimated	2016
Population trend	stable	poor	suspected	-
Rate of change over the past 10 years/3 generations (longer of the two periods)	24%	-	-	-
Generation length	13.5 years	-	-	-
Number of subpopulations	6	-	-	-
Percentage of mature individuals in largest subpopulation	95-99%	-	-	-

Population justification: The vast majority of the population (>95%) breeds on Natividad (Keitt 1998). On the San Benito islands, there used to be at least several thousand pairs (B. Tershy and B. Keitt in litt. 1999), but only 250-500 pairs were estimated in 1991 (Everett and Anderson 1991), and during the 2017-2019 breeding season, 121 breeding pairs were estimated (Sánchez et al. 2021a). On Guadalupe, the population was estimated at 2,500 pairs in 1991 (Everett and Anderson 1991), although may now be extirpated here (Sánchez et al. 2021a). In 1927, nesting was reported in Isla Rasa, Gulf of California, but the species is believed to be extirpated from that island by introduced rodents (Velarde et al. 2015). Nesting has been reported again since 2010; however, the size of the nesting population has not been determined (Velarde et al. 2015).
The total population estimated in 1998-1999 was around 80,000 pairs, and therefore 160,000 mature individuals. However, it is likely that the methods used in 1998-99 overestimated the population size, as counts of nests in selected areas were extrapolated to the whole surface of the island used by birds, without considering that there were large areas without any burrows.
In 2016, aerial photography and GIS were used to count the total number of occupied and unoccupied burrows in Natividad Island during the breeding season (Albores-Barajas et al. 2016). The total number of burrows counted, including occupied and abandoned burrows, was 56,400, but with a relatively low occupancy (between 75% and 50% depending on the area). The counts gave a figure of 37,900 (± 8500 SE) breeding pairs, equating to about 75,800 mature individuals. This figure was based on the initial occupancy of burrows in February 2016. Of these initially occupied burrows, 4,500 (about 12%) were later abandoned (Albores-Barajas et al. 2016). During the 2017-2019 breeding season, through further surveys on nest or burrow densities, 118,920 breeding pairs were counted on Natividad (Sánchez et al. 2021a), roughly equating to 238,000 mature individuals. Given the small populations present on other islands off Mexico's Pacific coast, the population is therefore placed in the band 200,000-299,999 mature individuals.

Trend justification: The species declined dramatically in the past owing to predation, in particular by introduced cats. On the principal breeding island, Natividad, there was a 15% decrease in habitat and a 13-20% loss in burrows between 1970 and the mid-1990s, with an estimated population decline of 4% per annum (Keitt 1998). However, eradication of cats from Natividad in 2002-2003 suggests that immediate threats to the species have now been significantly reduced and recruitment to the population may have increased. Nevertheless, the current trend has not been quantified. Although the counts from 2016 are much lower than in 1998-1999, data from 1998-1999 apparently overestimated the population; thus, the data do not seem to be comparable. However, as the eradication of cats from Natividad achieved a 90% reduction in mortality and a rapid recolonisation of cat-free areas (Keitt and Tershy 2003, Keitt et al. 2006), it is tentatively suspected that the population is currently stable or increasing slowly. Nevertheless, due to the species' longevity, the rapid declines of 4% per year in the large majority of the breeding population up until 2002 equate to a reduction of c.24% over the past three generations (40.5 years). Notably, bycatch in fisheries, habitat loss to infrastructure developments and habitat degradation through anthropogenic disturbance and introduced mammals and birds remain ongoing threats, and while their impacts on the population size have not been quantified it is possible that the population is still declining locally.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Canada	extant	vagrant			yes
Mexico	extant	native		yes	yes
USA	extant	native			yes

Country/Territory	IBA Name
Mexico	Archipiélago Bahía de los Angeles
Mexico	Archipiélago Loreto
Mexico	Área de San Quintín
Mexico	Bahía e Islas de San Jorge
Mexico	Bahía Magdalena-Almejas
Mexico	Bahía Todos Santos
Mexico	Ensenada de la Paz
Mexico	Isla Asunción
Mexico	Isla Cedros
Mexico	Isla Natividad
Mexico	Isla San Pedro Mártir
Mexico	Isla San Roque
Mexico	Islas Coronado
Mexico	Islas San Benito

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Caves and Subterranean Habitats (non-aquatic)	Caves	suitable	breeding
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 Moist	major	breeding
Altitude	0 - 100 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Biological resource use	Fishing & harvesting aquatic resources - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Slow, Significant Declines		Medium Impact: 7
		Stresses Species mortality
Human intrusions & disturbance	Recreational activities	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species disturbance, Ecosystem degradation
Human intrusions & disturbance	Work & other activities	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species disturbance
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Canis familiaris	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 - Capra hircus	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Whole (>90%)		Slow, Significant Declines		Past Impact
		Stresses Ecosystem degradation
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Equus asinus	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Whole (>90%)		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
		Past, Unlikely to Return		Majority (50-90%)		Rapid Declines		Past Impact
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Oryctolagus cuniculus	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Whole (>90%)		Slow, Significant Declines		Past Impact
		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		Whole (>90%)		Slow, Significant Declines		Past Impact
		Stresses Ecosystem degradation
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Corvus corax	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Negligible declines		Low Impact: 5
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Larus occidentalis	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Negligible declines		Low Impact: 5
		Stresses Species mortality
Pollution	Excess energy - Light pollution	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Residential & commercial development	Commercial & industrial areas	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Majority (50-90%)		Rapid Declines		Past Impact
		Stresses Species mortality
Residential & commercial development	Housing & urban areas	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Ecosystem degradation, Ecosystem conversion
Transportation & service corridors	Roads & railroads	Timing		Scope		Severity		Impact
		Past, Likely to Return		Minority (<50%)		Slow, Significant Declines		Past Impact
		Stresses Ecosystem degradation, Ecosystem conversion

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Recommended citation
BirdLife International (2024) Species factsheet: Black-vented Shearwater Puffinus opisthomelas. Downloaded from https://datazone.birdlife.org/species/factsheet/black-vented-shearwater-puffinus-opisthomelas on 23/11/2024.
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 23/11/2024.