• 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)	B2ab(iv,v)

Red List history

Year	Category	Criteria
2018	Endangered	B2ab(iv,v)
2016	Endangered	B2ab(iv,v)
2014	Endangered	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)	469,000 km2	medium
Extent of Occurrence (non-breeding)	1,760,000 km2	medium
Area of Occupancy (breeding/resident)	340 km2	medium
Number of locations	2-5	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	5000 mature individuals	medium	estimated	2012
Population trend	decreasing	poor	suspected	1974-2010
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	12.1 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: It is estimated to number fewer than 5,000 breeding birds (Birt et al. 2012), which are presumed to form one sub-population. Until further data are obtained, an estimate of 5,000 mature individuals is used in this assessment, which is assumed here to equate to c.7,500 individuals in total.

Trend justification: A number of colonies have been extirpated by introduced predators and alien invasive species continue to threaten some colonies. A number of other threatening processes are on-going, the combined effects of which are suspected to be causing a 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

Country/Territory	IBA Name
Mexico	Isla Asunción
USA	Channel Islands - Northern

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: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Climate change & severe weather	Temperature extremes	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Negligible declines		Low Impact: 5
		Stresses Indirect ecosystem effects, 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
Pollution	Industrial & military effluents - Oil spills	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses 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, Species mortality

---

Recommended citation
BirdLife International (2024) Species factsheet: Guadalupe Murrelet Synthliboramphus hypoleucus. Downloaded from https://datazone.birdlife.org/species/factsheet/guadalupe-murrelet-synthliboramphus-hypoleucus 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.