Blackish Oystercatcher Haematopus ater


Taxonomic note
Haematopus ater (del Hoyo and Collar 2014) was previously split as H. ater and H. bachmani 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. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.

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

Red List history
Year Category Criteria
2016 Least Concern
2014 Least Concern
Species attributes

Migratory status not a migrant Forest dependency Does not normally occur in forest
Land mass type Average mass 555 g

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 48,500,000 medium
Extent of Occurrence non-breeding (km2) 49,500,000 medium
Number of locations -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 20900-87300 poor estimated 2009
Population trend Unknown not applicable -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) - - -
Decline (10 years/3 generation past and future) - - -
Number of subpopulations - - -
Percentage in largest subpopulation - - -
Generation length (yrs) 13.7 - - -

Population justification: The population of H. a. ater is estimated to number 22,000-120,000 individuals, while that of H. a. bachmani is estimated to number 8,900-11,000 individuals, giving a total population of 30,900-131,000 individuals, roughly equating to 20,900-87,300 mature individuals.

Trend justification: The population trend is difficult to determine because of uncertainty over the extent of threats to the species (del Hoyo et al. 1996). The overall population trend of H. a. bachmani is stable (Wetlands International 2006). H. a. bachmani has undergone a large and statistically significant increase over the last 40 years in North America (213% increase over 40 years, equating to a 33% increase per decade; data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007).

Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Argentina N Extant Yes
Canada N Extant Yes
Falkland Islands (Malvinas) N Extant Yes
Mexico N Extant Yes
Peru N Extant Yes
Uruguay V Extant
USA N Extant Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Canada Frederick Island
Canada Scott Island Group
Canada Duke of Edinburgh Ecological Reserve
Canada Lepas Bay Islet
Canada Hippa Island
Canada Anthony Island
Canada Tian Bay/Port Louis Area
Canada Englefield Bay Islands
Canada Jervis Inlet/McRae Islet
Canada Chain Islets and Great Chain Islet
Canada Sidney Channel
Canada Porlier Pass
Canada Snake Island
Canada Little Qualicum Estuary to Nanoose Bay
Canada Mitlenatch Island
Canada Barkley Sound
Canada Cleland Island and Southeast Clayoquot Sound
Canada Kyuquot Channel Islets
Canada Checleset Bay
Canada Solander Island and Brooks Bay
Canada Gillam Island
Canada Smith Sound Islets
Canada Goose Island Group and Banks
Canada Moore and Byers Islands and Banks
Canada Lucy Islands
Canada Grey and Green islets
Canada Kunghit Island and Luxana Bay
Canada Rankine and Langtry Islands
Canada Skincuttle Inlet Islands
Canada Alder Island
Canada Ramsay and Northern Juan Perez Sound Islands
Canada Dodge Point and Gogit Passage Island Chain
Canada Laskeek Bay
Canada Cumshewa Inlet north to Sheldens Bay
Canada Skidegate Inlet
Canada McIntyre Beach and Rose Spit
Canada Major Brown Rock
USA Chiniak Bay
USA Farallon Islands
USA Kigul Islets Colonies
USA Cherni Island Complex Colonies

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Marine Intertidal Mud Flats and Salt Flats suitable non-breeding
Marine Intertidal Rocky Shoreline major resident
Marine Intertidal Shingle and/or Pebble Shoreline and/or Beaches suitable resident
Marine Intertidal Tidepools major resident
Altitude   Occasional altitudinal limits  

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

Recommended citation
BirdLife International (2021) Species factsheet: Haematopus ater. Downloaded from on 24/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from on 24/10/2021.