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

Taxonomic note
Hydrobates homochroa (del Hoyo and Collar 2014) was previously placed in the genus Oceanodroma.

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
-	A2ce+3ce	A2ce+3ce

Red List history

Year	Category	Criteria
2018	Endangered	A2ce+3ce
2016	Endangered	A2ce+3ce
2012	Endangered	A2ce+3ce
2010	Endangered	A2c,e; A3c,e; A4c,e
2008	Endangered	A2c,e; A3c,e; A4c,e
2007	Endangered
2005	Endangered
2004	Endangered
2000	Lower Risk/Near Threatened
1994	Lower Risk/Near Threatened
1988	Lower Risk/Least Concern

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	434,000 km2	medium
Extent of Occurrence (non-breeding)	205,000 km2	medium
Area of Occupancy (breeding/resident)	1,300 km2	medium
Number of locations	11-100	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	3500-6700 mature individuals	medium	estimated	2000
Population trend	decreasing	medium	estimated	1962-2010
Rate of change over the past 10 years/3 generations (longer of the two periods)	50-79%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	50-79%	-	-	-
Generation length	16 years	-	-	-

Population justification: The population is estimated to number 5,200-10,000 individuals, equivalent to 3,500-6,700 mature individuals.

Trend justification: A study on the South Farallon Islands found declines in breeding birds of 42% in 1972-1992 (Sydeman et al. 1998), equivalent to c.23% in 10 years or 78% over three generations, and declines in reproductive success have also been noted on Southeast Farallon Island. On Santa Cruz Island, nest-site monitoring during 1995-2006 showed declines in the number of breeding birds at two of five monitored sites (S. Wolf in litt. 2007). Declines are thought to have been driven by increased levels of predation and pollutants, though it may have been exaggerated by consecutive years of abnormal sea-surface temperatures leading to reduced colony attendance.

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

Country/Territory	IBA Name
USA	Channel Islands - Northern
USA	Farallon Islands
USA	Point Conception 120W34N
USA	Point Reyes - Outer

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
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
Rocky areas (eg. inland cliffs, mountain peaks)		major	breeding
Altitude		Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Climate change & severe weather	Storms & flooding	Timing		Scope		Severity		Impact
		Future		Minority (<50%)		Slow, Significant Declines		Low Impact: 3
		Stresses Ecosystem degradation, Reduced reproductive success
Human intrusions & disturbance	Recreational activities	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species disturbance, Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Mus musculus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Rattus rattus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Rapid Declines		Medium Impact: 6
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Athene cunicularia	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Larus occidentalis	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Tyto alba	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species mortality
Pollution	Agricultural & forestry effluents - Herbicides and pesticides	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Majority (50-90%)		Slow, Significant Declines		Past Impact
		Stresses Ecosystem degradation, Reduced reproductive success, Species mortality
Pollution	Excess energy - Light pollution	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Unknown		Unknown
		Stresses Species disturbance, Species mortality
Pollution	Industrial & military effluents - Oil spills	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Negligible declines		Low Impact: 5
		Stresses Ecosystem degradation, Reduced reproductive success, Species mortality

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Recommended citation
BirdLife International (2024) Species factsheet: Ashy Storm-petrel Hydrobates homochroa. Downloaded from https://datazone.birdlife.org/species/factsheet/ashy-storm-petrel-hydrobates-homochroa on 19/12/2024.
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 19/12/2024.