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

Taxonomic note
Synthliboramphus hypoleucus and S. scrippsi (del Hoyo and Collar 2014) were previously lumped as S. hypoleucus following Sibley and Monroe (1990, 1993).

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.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	-	B2ab(iv,v)

Red List history

Year	Category	Criteria
2020	Vulnerable	B2ab(iv,v)
2018	Vulnerable	B2ab(iv,v)
2016	Vulnerable	B2ab(iv,v)
2014	Vulnerable	B2ab(iv,v)
2012	Not Recognised
2008	Not Recognised
2004	Not Recognised
2000	Not Recognised
1994	Not Recognised
1988	Not Recognised

Migratory status	not a migrant	Forest dependency	does not normally occur in forest
Land-mass type		Average mass	167 g

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	217,000 km2	medium
Extent of Occurrence (non-breeding)	1,440,000 km2	medium
Area of Occupancy (breeding/resident)	62 km2	medium
Number of locations	6-10	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	10000-19999 mature individuals	medium	estimated	2015
Population trend	decreasing	poor	inferred	2008-2024
Rate of change over the past 10 years/3 generations (longer of the two periods)	10-19%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	10-19%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	10-19%	-	-	-
Generation length	5.18 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: Birt et al. (2012) estimate the total number of breeding pairs to be in excess of 6,500, which equated to 13,000 mature individuals. Partners in Flight (2019) estimate the population at 15,000, hence it is placed here in the band for 10,000-19,999 mature individuals, assumed to equate to 15,000-30,000 individuals in total.

Trend justification: A number of colonies have been extirpated by introduced predators, particularly throughout the islands of western Baja California however, many of the extirpated colonies have reestablished and recovered in recent decades following the control and removal of invasive predators (Bedolla-Guzmán et al. 2019). Alien invasive species continue to threaten some colonies however the eradication of cats and other invasive predators on many breeding islands since the mid-1990s has reversed numerous such trends, generating population increases, as noted at Anacapa Island, California (4.45 increase in nesting 2011-2014 [Whitworth and Carter 2017, Bedolla-Guzmán et al. 2019]), likely at San Miguel Island (2004-2015 [Whitworth and Carter 2018]) and on a number of islands off the coast of western Baja California (Islas Coronado, Todos Santos, San Martín and San Benito [Whitworth et al. 2020]). A number of other threatening processes are however on-going; the combined effects of which are suspected to be inducing an overall moderate decline in this species's global population. 

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	yes

Country/Territory	IBA Name
Mexico	Bahía Todos Santos

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Marine Coastal/Supratidal	Sea Cliffs and Rocky Offshore Islands	major	breeding
Marine Neritic	Pelagic	major	resident
Marine Oceanic	Epipelagic (0-200m)	suitable	resident
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: (large scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species disturbance, Species mortality, Other
Climate change & severe weather	Habitat shifting & alteration	Timing		Scope		Severity		Impact
		Future		Whole (>90%)		Slow, Significant Declines		Low Impact: 5
		Stresses Indirect ecosystem effects, Ecosystem degradation, Reduced reproductive success, Species mortality
Human intrusions & disturbance	Work & other activities	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species disturbance, Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Felis catus	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Rattus rattus	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Peromyscus maniculatus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Tyto alba	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Pollution	Excess energy - Light pollution	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species disturbance, Reduced reproductive success, Other
Pollution	Industrial & military effluents - Oil spills	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Negligible declines		Low Impact: 5
		Stresses Ecosystem degradation, Species mortality
Pollution	Industrial & military effluents - Type Unknown/Unrecorded	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Unknown		Unknown		Past Impact
		Stresses Reduced reproductive success

---

Recommended citation
BirdLife International (2024) Species factsheet: Scripps's Murrelet Synthliboramphus scrippsi. Downloaded from https://datazone.birdlife.org/species/factsheet/scrippss-murrelet-synthliboramphus-scrippsi on 24/12/2024.
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 24/12/2024.