Data Zone
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.
| Critically Endangered | Endangered | Vulnerable |
|---|---|---|
| - | - | - |
| Year | Category | Criteria |
|---|---|---|
| 2020 | Near Threatened | D2 |
| 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 |
| Migratory status | full migrant | Forest dependency | does not normally occur in forest |
| Land-mass type |
continent |
Average mass | - |
| Estimate | Data quality | |
|---|---|---|
| Extent of Occurrence (breeding/resident) | 1,100,000 km2 | medium |
| Extent of Occurrence (non-breeding) | 3,560,000 km2 | medium |
| Area of Occupancy (breeding/resident) | 43 km2 | medium |
| Number of locations | 5 | - |
| Severely fragmented? | no | - |
| Estimate | Data quality | Derivation | Year of estimate | |
|---|---|---|---|---|
| Population size | 350000 mature individuals | medium | estimated | 2016 |
| Population trend | unknown | poor | - | 1977-2010 |
| Generation length | 9.65 years | - | - | - |
Population justification: Larus heermanni is estimated to have a population of 350,000 mature individuals (Partners in Flight 2019), ~92% of which nest on Isla Rasa, Mexico (Burger and Gochfeld 1996). 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). There are further throughout to be 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) however, more recent surveys are required to confirm such figures.
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). These surveys however cover less than 50% of the species' range in North America. 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. An 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 | Presence | Origin | Resident | Breeding visitor | Non-breeding visitor | Passage migrant |
|---|---|---|---|---|---|---|
| Canada | extant | native | yes | |||
| Costa Rica | extant | vagrant | yes | |||
| Guatemala | extant | vagrant | ||||
| Mexico | extant | native | yes | |||
| USA | extant | native | yes |
| 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 |
| 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 | ||||||
|
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| 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 | ||||||
|
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| Climate change & severe weather | Temperature extremes | Timing | Scope | Severity | Impact | ||||
| Ongoing | Majority (50-90%) | Causing/Could cause fluctuations | Medium Impact: 6 | ||||||
|
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| Human intrusions & disturbance | Recreational activities | Timing | Scope | Severity | Impact | ||||
| Ongoing | Majority (50-90%) | Slow, Significant Declines | Medium Impact: 6 | ||||||
|
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| 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 | ||||||
|
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| 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 | ||||||
|
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| Pollution | Industrial & military effluents - Type Unknown/Unrecorded | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
|
|||||||||
| Purpose | Scale |
|---|---|
| Pets/display animals, horticulture | international |
Recommended citation
BirdLife International (2024) Species factsheet: Heermann's Gull Larus heermanni. Downloaded from
https://datazone.birdlife.org/species/factsheet/heermanns-gull-larus-heermanni 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.