Data Zone
Justification of Red List category
Although this species has a comparatively small breeding range size for a shorebird (extent of occurrence c. 950,000 km2), this still far exceeds Criteria B thresholds. It also has a large estimated population size (3,500,000 mature individuals; Partners in Flight 2023), and so does not approach Criteria C or D thresholds. The population trend is suspected to be declining, but not at a rate that meets or approaches thresholds under Criterion A. Western Sandpiper is therefore listed as Least Concern.
Population justification
The species has a large estimated population size (3,500,000 mature individuals; Partners in Flight 2023).
Trend justification
Considering its population trend over three generations (c. 14 years), data from the Christmas Bird Count (Meehan et al. 2022) indicate that it has remained broadly stable, albeit with interannual fluctuations. Over the same period, the Breeding Bird Survey (Ziolkowski et al. 2022) reported a decline, but with huge confidence intervals. In the non-breeding season, non-significant declines were recorded by both the Migratory Shorebird Project (unpublished data) and eBird (Fink et al. 2023). Although the population may be declining, it does not currently appear to be declining at a rate approaching Criterion A thresholds.
Western Sandpipers breed in Alaska (USA) from Dillingham to Point Barrow and Camden Bay, including St. Lawrence Island and adjacent Siberia (Russia). Birds migrate south to chiefly winter along the Pacific coast from California to Peru, with some birds as far north as southern British Columbia (Canada) (Frank et al. 2020).
Drivers of suspected population declines are not well understood.
Habitat loss and degradation are significant threats to C. mauri, particularly through the drainage of wetlands at wintering and stopover sites for urban development, agriculture, and shrimp farming. In the Upper Bay of Panama, urbanisation from Panama City has led to the drainage of the Costa del Este marshes (Frank et al. 2020). Wetland quality has also declined due to the construction of channels and dikes. Additionally, the colonisation by Spartina alterniflora in North American Pacific coast estuaries has the potential to reduce feeding areas by up to 80%, leading to fewer critical foraging and roosting areas (Frank et al. 2020, Stralberg et al. 2004). Environmental contamination, including pollutants from oil spills and agricultural chemicals, poses a threat to C. mauri. Oil spills are a risk along the North American coast, where many stopover and staging sites are near shipping channels and refineries. Agricultural runoff introduces pesticides and other harmful chemicals into their habitats, potentially affecting their health and reproduction (Fernández et al. 2010).
Human disturbance from recreational activities (e.g., pedestrians, motorised vehicles, watercraft and pets), coastal development, and shellfish harvesting disrupts the species during migration and wintering periods. Such disturbances lead to energetic costs and habitat displacement, impacting their overall fitness and survival (Fernández et al. 2010).
Climate change has by some been identified as a concern (Frank et al. 2020), although available breeding habitat based on predicted distribution under future climate change scenarios is predicted to increase by between 90% (RCP 4.5) and 83% (RCP 8.5) by 2070 (Wauchope et al. 2017).
Conservation Actions Underway
Protected under the Migratory Birds Act (1927). This species' non-breeding population is part-covered by the Christmas Bird Count (Meehan et al. 2022).
Conservation Actions Proposed
Priority conservation actions needed for Western Sandpipers include protecting, restoring, and enhancing critical habitats along the Pacific coast of northwest Mexico and other key areas. This includes maintaining diverse salt pond habitats in San Francisco Bay, California, and formally recognizing important sites for protection at local, regional, and international scales. Implementing conservation easements and voluntary conservation plans, especially in Mexico, Panama, and other Latin American countries, is essential. Coordination among stakeholders and incorporating shorebird needs into existing conservation plans are also crucial for effective conservation (Fernández et al. 2010).
Text account compilers
Chad, E., Ekstrom, J., Butchart, S.
Recommended citation
BirdLife International (2024) Species factsheet: Western Sandpiper Calidris mauri. Downloaded from
https://datazone.birdlife.org/species/factsheet/western-sandpiper-calidris-mauri on 26/12/2024.
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 26/12/2024.