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

Taxonomic note
Onychoprion aleuticus (del Hoyo and Collar 2014) was previously placed in the genus Sterna as S. aleutica.

Taxonomic source(s)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: http://www.aerc.eu/DOCS/Bird_taxa_of_the_WP15.xls.
Cramp, S. and Simmons, K.E.L. (eds). 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. 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
-	-	A2bcde+3bcde+4cde

Red List history

Year	Category	Criteria
2020	Vulnerable	A2bcde+3bcde+4cde
2018	Vulnerable	A2bcde+3cde+4bcde
2017	Vulnerable	A2bcde+3cde+4bcde
2016	Least Concern
2012	Least Concern
2009	Least Concern
2008	Least Concern
2004	Least Concern
2000	Lower Risk/Least Concern
1994	Lower Risk/Least Concern
1988	Lower Risk/Least Concern

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	6,660,000 km2
Extent of Occurrence (non-breeding)	225,000 km2
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	31000 mature individuals	poor	estimated	2015
Population trend	decreasing	-	inferred	2000-2026
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	8.53 years	-	-	-

Population justification: Previous published population estimates for Alaska ranged from 9,000 to 12,000 birds, and estimates for Russia ranged from 7,200 to 13,000, although they were based on data that are more than 20 years old (H. Renner in litt. 2013). Wetlands International estimated a total population of 17,000-20,000 individuals in 2005, including 9,500 birds in Alaska (Wetlands International 2020), based on data from the U.S. Fish and Wildlife Service (2006), and the total population was therefore placed in the range 11,000-13,000 mature individuals. Partners in Flight (2019) placed the number of mature individuals at 22,000 based on 2015 estimates however, a subsequent range-wide assessment of population and trends estimated a minimum worldwide breeding population of 31,131 birds across 202 colonies, with 18% (5,529 birds in 110 colonies) in Alaska and 82% (25,602 birds in 92 colonies) in Russia (Renner et al. 2015). It does not account for colonies that have not been surveyed in recent years or for the fact that the surveys conducted were neither systematic nor inclusive of all potential habitats (Renner et al. 2015) and thus the total population may be higher. Based on the minimum total recorded by Renner et al. (2015), the global population estimate has therefore been revised to 31,000 mature individuals.

Trend justification:

Numbers at known colonies in Alaska have declined by 8.1% annually since 1960 with a 93% decline noted over a three decade period from the mid-1980s onwards (Renner et al. 2015, Corcoran 2017). Large colonies experienced larger declines than small colonies. Trends at known colonies within discrete geographic regions of Alaska (Aleutian Islands, Bering Sea, Chukchi Sea, Gulf of Alaska and Kodiak Island) were consistently negative. It is possible that observed trends in Alaska could be explained by the establishment of large, undiscovered colonies in new locations within Alaska, or major shifts between Alaska and Russia, but at present this seems unlikely. The geographic distance would be far greater than any typical breeding dispersal distance of other tern species, and there is no precedence for terns to move their established breeding sites in a biased direction from such a wide geographic scale. All the recently discovered colonies in Alaska are of small size, and unless there are some major colonies remaining to be discovered, it is unlikely to account for the observed declines (M. Rauzon / Pacific Seabird Group in litt. 2017). 

Quantitative trend information from the colonies in the Russian Far East remains lacking, but declines have been reported in several colonies in the Anadyr and Chukotka region (C. Zockler in litt. 2014). However, numbers in some regions in Russia appear to have increased substantially in recent decades, especially on Sakhalin Island and the southern coast of the Koryak Highland (Renner et al. 2015). 

It is difficult to determine the overall trend, but it is unlikely that the extremely rapid declines observed in Alaska have been outweighed by the trend in Russia and a rapid overall decline is therefore suspected to be taking place.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Canada	extant	native				yes
Hong Kong (China)	extant	native				yes
Indonesia	extant	native			yes
Japan	extant	native				yes
Malaysia	extant	native			yes
Papua New Guinea	extant	native			yes
Philippines	extant	native			yes
Russia	extant	native		yes
Russia (Asian)	extant	native		yes
Singapore	extant	native			yes
Thailand	extant	native			yes
United Kingdom	extant	vagrant
USA	extant	native		yes

Country/Territory	IBA Name
Russia (Asian)	Bol'shaya River Estuary
Russia (Asian)	Korfa Gulf (northern part)
Russia (Asian)	Kronotskiy Gulf
Russia (Asian)	Meechkyn spit and adjacent plain
Russia (Asian)	Nerpich'ye Lake and Kamchatka River delta
Russia (Asian)	Nevskoye Lake
Russia (Asian)	North-east Sakhalin lagoons
Russia (Asian)	Schast'ya Gulf
Russia (Asian)	Shantarskiye Islands
Russia (Asian)	Udskaya Bay
USA	Blacksand Spit Colony
USA	East Copper River Delta Colonies
USA	Eastern Kodiak Island Marine
USA	Entrance Point Colony
USA	Goodnews Bay Colony
USA	Nelson Lagoon Colonies
USA	Noatak River Delta Colony
USA	Riou Spit Colony
USA	Safety Sound
USA	Tiedeman Slough Colony

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Grassland	Tundra	suitable	breeding
Marine Intertidal	Sandy Shoreline and/or Beaches, Sand Bars, Spits, Etc	major	breeding
Marine Intertidal	Shingle and/or Pebble Shoreline and/or Beaches	major	breeding
Marine Neritic	Pelagic	suitable	non-breeding
Marine Neritic	Pelagic	suitable	breeding
Marine Oceanic	Epipelagic (0-200m)	suitable	non-breeding
Rocky areas (eg. inland cliffs, mountain peaks)		suitable	breeding
Wetlands (inland)	Bogs, Marshes, Swamps, Fens, Peatlands	suitable	breeding
Altitude		Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Biological resource use	Hunting & trapping terrestrial animals - Intentional use (species is the target)	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Reduced reproductive success
Climate change & severe weather	Habitat shifting & alteration	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Unknown		Unknown
		Stresses Indirect ecosystem effects, Ecosystem degradation, Reduced reproductive success
Human intrusions & disturbance	Recreational activities	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species disturbance, Reduced reproductive success
Human intrusions & disturbance	Work & other activities	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		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%)		Unknown		Unknown
		Stresses Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Rattus norvegicus	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 - Vulpes lagopus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Vulpes vulpes	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Reduced reproductive success, Species mortality

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Recommended citation
BirdLife International (2024) Species factsheet: Aleutian Tern Onychoprion aleuticus. Downloaded from https://datazone.birdlife.org/species/factsheet/aleutian-tern-onychoprion-aleuticus 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.