NT
Heermann's Gull Larus heermanni



Taxonomy

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.

IUCN Red list criteria met and history
Red List criteria met
Critically Endangered Endangered Vulnerable
- - -

Red List history
Year Category Criteria
2018 Near Threatened D2
2016 Near Threatened D2
2012 Near Threatened D2
2010 Near Threatened D2
2008 Near Threatened D2
2006 Near Threatened
2004 Near Threatened
2000 Lower Risk/Near Threatened
1994 Lower Risk/Near Threatened
1988 Lower Risk/Least Concern
Species attributes

Migratory status full migrant Forest dependency Does not normally occur in forest
Land mass type Land-mass type - continent
Average mass -
Extent of occurrence (EOO)

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 1,100,000 medium
Extent of Occurrence non-breeding (km2) 3,560,000 medium
Extent of Occurrence breeding/resident (km2) 43 medium
Number of locations 5 -
Fragmentation -
Population and trend
Estimate Data quality Derivation Year of estimate
No. of mature individuals 300000 medium estimated 2016
Population trend Unknown poor observed -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) 0 - - -
Decline (10 years/3 generation past and future) 0 - - -
Number of subpopulations - - -
Largest subpopulations - - -
Generation length (yrs) 11.5 - - -

Population justification: Larus heermanni has a population of approximately 283,000 to 300,000 breeding adults (Kushlan et al. 2002), 92% of which nest on Isla Rasa, Mexico (Burger and Gochfeld 1996). There are 150 pairs on George Island, 1,500 on Cholluda (Burger and Gochfeld 1996), 4,000 on Cardonosa and 200 breeding individuals on San Il de Fonso (Velarde 1999). Numbers on Isla Rasa are similar to estimates in the late 1960s, but there have been significant fluctuations with a low of 55,000 pairs in 1975 (Burger and Gochfeld 1996).

Trend justification: The overall population trend is fluctuating (Delany and Scott 2006). This species has undergone a large and statistically significant increase over the last 40 years in North America (361% increase over 40 years, equating to a 46.6% increase per decade; data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). Note, however, that these surveys cover less than 50% of the species' range in North America. However, in the last eight years, almost total breeding failure has occurred in five nesting seasons. This is mainly due to environmental anomalies, that result in lack of food availability and, secondarily to overfishing of small pelagic fish (mainly Pacific sardine) their main food sources. One analysis of the trend of the population of this species is in process, to be able to predict the rate of population fluctuation over several years.


Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Canada N Extant Yes
Costa Rica V Extant Yes
Guatemala V Extant
Mexico N Extant Yes
USA N Extant Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Mexico Bahia de Ceuta-Cospita
Mexico Carricitos-Cacaxtla-Río Piaxtla
Mexico Estero Cardonal
Mexico Estero Santa Cruz
Mexico Farallon San Ignacio
Mexico Isla Angel de la Guarda
Mexico Isla Benitos
Mexico Isla Isabel
Mexico Isla Rasa
Mexico Isla San Pedro Martir
Mexico Islas Marietas
USA Channel Islands - Northern
USA North San Diego Lagoons
USA Point Mugu
USA Port Angeles Harbor/Ediz Hook
USA San Clemente Island
USA San Diego Bay - South
USA Santa Clara River Valley

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Marine Coastal/Supratidal Coastal Brackish/Saline Lagoons/Marine Lakes major non-breeding
Marine Coastal/Supratidal Sea Cliffs and Rocky Offshore Islands major breeding
Marine Intertidal Rocky Shoreline major breeding
Marine Intertidal Sandy Shoreline and/or Beaches, Sand Bars, Spits, Etc suitable non-breeding
Marine Intertidal Sandy Shoreline and/or Beaches, Sand Bars, Spits, Etc suitable breeding
Marine Intertidal Shingle and/or Pebble Shoreline and/or Beaches suitable non-breeding
Marine Intertidal Shingle and/or Pebble Shoreline and/or Beaches suitable breeding
Marine Intertidal Tidepools major breeding
Marine Neritic Macroalgal/Kelp major non-breeding
Marine Neritic Macroalgal/Kelp major breeding
Marine Neritic Pelagic suitable non-breeding
Marine Neritic Pelagic suitable breeding
Marine Neritic Seagrass (Submerged) major non-breeding
Marine Neritic Seagrass (Submerged) major breeding
Marine Neritic Subtidal Loose Rock/pebble/gravel major non-breeding
Marine Neritic Subtidal Loose Rock/pebble/gravel major breeding
Marine Neritic Subtidal Rock and Rocky Reefs major non-breeding
Marine Neritic Subtidal Rock and Rocky Reefs major breeding
Marine Neritic Subtidal Sandy major non-breeding
Marine Neritic Subtidal Sandy major breeding
Marine Neritic Subtidal Sandy-Mud major non-breeding
Marine Neritic Subtidal Sandy-Mud major breeding
Altitude 0 - 50 m Occasional altitudinal limits  

Threats & impact
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 Majority (50-90%) Causing/Could cause fluctuations Medium Impact: 6
Stresses
Indirect ecosystem effects, Reduced reproductive success
Biological resource use Hunting & trapping terrestrial animals - Intentional use (species is the target) Timing Scope Severity Impact
Ongoing Minority (<50%) Negligible declines Low Impact: 4
Stresses
Reduced reproductive success, Species mortality
Climate change & severe weather Temperature extremes Timing Scope Severity Impact
Ongoing Majority (50-90%) Causing/Could cause fluctuations Medium Impact: 6
Stresses
Ecosystem degradation, Reduced reproductive success, Species mortality
Human intrusions & disturbance Recreational activities Timing Scope Severity Impact
Ongoing Majority (50-90%) Slow, Significant Declines Medium Impact: 6
Stresses
Species disturbance
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%) Slow, Significant Declines Low Impact: 5
Stresses
Reduced reproductive success
Pollution Industrial & military effluents - Type Unknown/Unrecorded Timing Scope Severity Impact
Ongoing Minority (<50%) Negligible declines Low Impact: 4
Stresses
Reduced reproductive success

Utilisation
Purpose Primary form used Life stage used Source Scale Level Timing
Pets/display animals, horticulture - - International Non-trivial Recent
Pets/display animals, horticulture - - International Non-trivial Recent

Recommended citation
BirdLife International (2019) Species factsheet: Larus heermanni. Downloaded from http://www.birdlife.org on 20/03/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/03/2019.