By Emma Hui, Biological Sciences ‘26 

INTRODUCTION

The migration of Western Sandpipers from the high Arctics to Southern California has always been a treasured gem in the fall. Yet as decades roll by, Western Sandpiper populations have been in continuous decline, and the rugged coastline of the Pacific Northwest seems lonelier than ever [1]. As a migratory bird species, the Western Sandpiper plays crucial ecological roles as an indicator of ecosystem health and by connecting diverse habitats across continents.

The purpose of this essay is to introduce the ongoing decline of Western Sandpiper populations in recent years, with a particular focus on the population decline in North America. This paper will provide an overview of Western Sandpiper migration and population changes, examine the potential causes behind the dynamics, and analyze the decline’s corresponding ecological effects. I will also explore possible remedies for the issue from the perspectives of habitat restoration, conservation, and legislative measures. The ultimate objective of this essay is to raise awareness and promote action for the ecological conservation of Western Sandpipers before it is too late.

Background

Western Sandpipers are small migratory birds that breed in high Arctic regions of Alaska and Siberia and migrate south to the Pacific coast of North and South America for winter. Their migration is 15,000 kilometers every year along the Pacific Flyway, spanning from Alaska to South America. During winter, their nonbreeding season, they move to coastal areas with mudflats, estuaries, and beaches, which allows the birds to rest and forage for food. In spring, the Western Sandpipers take a similar reverse migration route, stopping at critical habitats along the way until they reach the treeless Arctic tundra. As they fly north, they breed in Northwestern Alaska and Eastern Siberia, and each female lays three to four eggs. 

They measure 6 to 7 inches in length and have reddish brown-gold markings on their head and wings. Their most salient features are their slender pointed bills and long legs. The bills are adapted for foraging crustaceans, insects, and mollusks in muddy areas, while their pair of long but thin legs are used for wading in shallow water and sand. These small, darting birds can be seen in tidal areas, foraging in mudflats for invertebrates and biofilms at low and middle tides with other shorebird communities.

Having multiple species foraging together makes shorebirds among the most difficult birds to identify, especially with many species being quite similar in morphology as well as call. As they always smoothly blend into the community, it is not surprising that the population decline of the small Western Sandpipers went unnoticed at first and was reported only when changes in population levels became more obvious.

Causes of Western Sandpiper population decline

The population decline in the Western Sandpiper population has been continuous throughout the past decade. According to the North American Breeding Bird Survey, which monitors populations of breeding birds across the continent, the Western Sandpiper had a relatively stable population trend in the United States from 1966 to 2015, with an annual population decline of 0.1% over this period [2]. In more recent years, a research team in British Columbia, Canada that investigates estuary condition change has noticed the decline in Western Sandpipers inhabiting the Fraser River estuary. Observing the Western Sandpiper population during Northern migration on the Fraser River estuary, the team concluded a 54% decline in Western Sandpipers over the entire study period of 2019 []. The negative trend in migrating Western Sandpipers in North America is consistent with this study in Fraser River. A study using Geolocator wetness data to detect periods of migratory flight examined the status and trends of 45 shorebird species in North America, including the Western sandpiper. The author found that the Western Sandpiper population in the U.S. declined by 37% from 1974 to 2014, with an estimated population of 2,450,000 individuals in 2014 compared to 3,900,000 individuals in 1974.[3]

Currently, on BirdLife International Data Zone, Western Sandpipers have been labeled “least concern” for their wide range of inhabitation, but their population is decreasing. The species faces threats from habitat loss and degradation, pollution, and disturbance, particularly in its wintering and stopover sites along the North American Pacific coast. Habitat loss due to human activities, namely agricultural expansion and oil development, has contributed to the loss and degradation of Western Sandpiper’s breeding, wintering, and stopover habitats. [4] The loss of these habitats has led to reductions in breeding success, migration stopover times, and overwintering survival of Western Sandpipers. Meanwhile, Western Sandpipers are constantly exposed to various pollutants including pesticides, heavy metals, oil spills, and plastics. These contaminants affect Western Sandpiper’s health and reproductive success directly and impact Western Sandpiper’s prey and predators. As habitat loss leads to reduced food resources, Western Sandpipers’ overall health is negatively impacted, making them even more vulnerable to pollutants and contaminants. 

Climate change is also expected to have future impacts on the species. One possible shift that climate change can impose is on the timing, intensity, and distribution of precipitation. The precipitation shifts have caused droughts and floods in areas that are breeding and stopover habitats for Western Sandpiper and other shorebirds, leading to reduced breeding success and increased mortality in the Western Sandpiper population. Climate change also imposes effects on sea level, temperature, and the frequency and severity of extreme weather, which can all affect the quality of breeding habitat and food availability for Western Sandpipers.

The interactions between these factors are complex and can lead to a feedback loop of negative impacts on the population. As habitat loss leads to reduced food resources, Western Sandpipers’ overall health is negatively impacted, making them even more vulnerable to pollutants and contaminants.

Effects of Western Sandpiper population decline

The decline of the Western Sandpiper population can have significant impacts on ecosystems. As a migratory shorebird, the Western Sandpiper’s ecological role lies in coastal environments; by preying on invertebrates along the coastal shoreline, the Western Sandpipers control their prey species populations and balance the ecosystem. The decline of the Western Sandpiper population can lead to an increase in their prey species such as polychaete worms and bivalves, which can lead to changes in the composition of other species that prey on similar invertebrates and perturbates the ecosystem’s equilibrium. Furthermore, many predator species, such as falcons and owls, depend on the Western Sandpiper as a food source, and their decline will negatively impact these predator species.

Aside from predator-prey dynamics, Western Sandpipers also forage with many other migratory shorebird species in muddy areas along the coast. These birds, such as the Marble Godwit and the Red Knot, depend on the same stopover habitats as the Western Sandpiper during their own migrations and thus compete for similar resources. As the Western Sandpiper population declines, changing interspecies dynamics will shift the survival and reproductive success of other species, disturbing the equilibrium of the stopover ecosystems.

Western Sandpipers are a popular bird species among birdwatchers and nature enthusiasts, and their migration stopover sites in the Pacific Northwest and Alaska have an important role in ecotourism and its respective economic and cultural values. The economic impact of Western Sandpiper ecotourism in the Copper River Delta, Alaska was evaluated to produce over $1.5 million in revenue and 100 jobs. [5]

Overall, the decline of the Western Sandpiper population can have a complex and far-reaching impact on both the ecosystem and human society. By interacting with native species and migratory species in their natural habitats, the Western Sandpiper’s role deeply interweaves within the ecosystem.

Conservation efforts and solutions

Conservation efforts to protect and restore Western Sandpiper populations are critical in maintaining ecosystem health. One of the main strategies to protect the Western Sandpiper is to conserve their stopover sites and breeding grounds by monitoring and researching invasive species and coastal development. Aside from consistent restoration of degraded habits after human disturbance, prevention of further human development in Western Sandpiper habitats is also critical in maintaining the habitat’s health.

Educating the public about the importance of Western Sandpipers and their habitats is a crucial aspect in raising awareness and gaining support for conservation efforts. Outreach such as public lectures, bird festivals, and school tours are great opportunities to connect humans to the beautiful avian community and improve public consciousness regarding ecosystem conservation. An example includes the Monterey Bay Birding Festival, which is an annual festival in California during shorebird fall migration season. This festival promotes awareness of shorebirds with its educational workshops and bird tours.[6]

Currently, conservation efforts of shorebird populations face limitations in funding and coordination. Significant funding efforts are required to restore what has been lost, but limited budgets restrict the scope and effectiveness of conservation approaches. In addition, since conservation efforts are implemented on a site-by-site basis, there is a need for improved coordination among different agencies to solve problems together. Potential solutions to the need for adequate funding and coordination are the implementation of stronger policies of avian conservation and habitat conservation as well as the encouragement of sustainable tourism and outreach efforts.

CONCLUSION

The Western Sandpiper population in North American tidal areas has been experiencing a significant decline in recent years, largely due to human activities and subsequent climate change. Population changes of this small, long-legged shorebird affect many species that interact and co-exist with them in the coastal ecosystem. They are one of the most abundant shorebird species in North America and play a vital part in the ecological and cultural values along the coast. Population dynamics vary year to year and between different populations, and increasing efforts in the monitoring and conservation of the Western Sandpiper community and their respective habitats is essential to ensuring the species’ survival. We need to investigate the causes behind the population’s decline in recent years and take action before the negative effects have gone too far and these ballerinas of the beach are unable to recover.

REFERENCES

[1] Andres, B., Smith, B. D., Morrison, R. I. G., Gratto-Trevor, C., Brown, S. C., Friis, C. A., … Paquet, J. (2013). Population estimates of North American shorebirds, 2012. Wader Study Group Bulletin, 119, 178-194.

 [2] The Cornell Lab of Ornithology. (n.d.). Western Sandpiper Overview, All About Birds, Cornell Lab of Ornithology. Cornell University. https://www.allaboutbirds.org/guide/Western_Sandpiper/overview

[3] The Wader Study Group. (n.d.). Geolocator Wetness Data Accurately Detect Periods of Migratory Flight in Two Species of Shorebird. https://www.waderstudygroup.org/article/9619/

[4] Smith, B. D., Andres, B. A., & Morrison, R. I. G. (2017). Declines in shorebird populations in North America. Wader Study, 124(1), 1-11.

[5] Vogt, D. F., Hopey, M. E., Mayfield, G. R. III, Soehren, E. C., Lewis, L. M., Trent, J. A., & Rush, S. A. (2012). Stopover site fidelity by Tennessee warblers at a southern Appalachian high-elevation site. The Wilson Journal of Ornithology, 124(2), 366-370. https://doi.org/10.1676/11-107.1

[6] Cornell Lab of Ornithology. (2019, September 24). Monterey Bay Festival of Birds [Web log post]. All About Birds. https://www.allaboutbirds.org/news/event/monterey-bay-festival-of-birds/#

 [7] Haig, S. M., Kaler, R. S. A., & Oyler-McCance, S. J. (2014). Causes of contemporary population declines in shorebirds. The Condor, 116(4), 672-681.

 [8] Kallenberg, M. (2021). The 121st Christmas Bird Count in California. Audubon. https://www.audubon.org/news/the-121st-christmas-bird-count-california

 [9] Reiter, P. (2001). Climate change and mosquito-borne disease. Environmental Health Perspectives, 109(1). https://doi.org/10.1289/ehp.01109s1141

 [10] Sandpipers Go with the Flow: Correlations … – Wiley Online Library. (n.d.). Wiley Online Library. https://doi.org/10.1002/ece3.7240

[11] The Wader Study Group. (n.d.). Comparison of Shorebird Abundance and Foraging Rate Estimates from Footprints, Fecal Droppings an,d Trail Cameras. https://www.waderstudygroup.org/article/13389/

 [12] US Fish and Wildlife Service. (2022). Western Sandpiper (Calidris mauri). https://www.fws.gov/species/western-sandpiper-calidris-mauri 

[13] Wamura, T., Iwamura, T., & Possingham, H. P. (2013). Migratory connectivity magnifies the consequences of habitat loss from sea-level rise for shorebird populations. Proceedings of the Royal Society B, 280(1761), 20130325. https://doi.org/10.1098/rspb.2013.0325