Western Sandpipers (Calidris mauri) are small, round shorebirds that have staked their claim over the West Coast. These chunky little ‘peeps’ (collective nickname for sandpipers) are one of the most numerous shorebirds in the Pacific North Coast of America (Natureweb, 2022). They delight British Columbians each year when they grace us with their presence as they play international hopscotch. There is far more to Western Sandpipers than meets the eye, even if you have to squint to see them.
Credit: Tim Lens
CLASS: AVES
ORDER: CHARADRIIFORMES
FAMILY: SCOLOPACIDAE
GENUS: CALIDRIS
SPECIES: C. MAURI
Identifying a Western Sandpiper
Credit: Dorian AndersonCredit: Mike CameronCredit: Ian Davies
Breeding Adult
Non-Breeding Adult
Juvenile
During their breeding season (spring/summer), Western Sandpipers sport rufous highlights on their crown, cheek and their backs. Their backs are a mosaic of black, orange and brown, while their chests are adorned with black arrows. Although in their non-breeding season (winter), they dial it back with a more plain, conservative look: grey uppers and white below. Juveniles seem to be an amalgamation of the two, their bellies white and their uppers grey with hints of rust and gold (All About Birds, 2024).
Distinguish them further from other peeps by checking for field marks such as: black legs and long bill, that droops lightly at the tip (All About Birds, 2024).
At 22-35g, adult Western Sandpipers weigh less than a slice of bread, and measure 14-17cm, no longer than a crisp $5 dollar bill (All About Birds, 2024).
Listen Up: Vocalizations of the Western Sandpiper
Their Songs are filled with buzzy trills and strings of ‘tweer‘ sounds, while their calls are short, harsh ‘jeets‘ (All About Birds, 2024). Next time you’re at the beach, listen for the following adorable, yet powerful sounds:
Songs:
Credit: Peter Boesman
Calls:
Credit: Patrick Aberg
Small Birds, Big Migration
Credit: Jason Puddifoot
Western Sandpipers have made themselves known to North and South Americans alike. They breed in the dry tundra of Southern Siberia and Western Alaska, and like many retired Canadians, they spend their winters someplace warmer. Their overwintering areas range from California, all the way down to Peru (Birds Canada, 2023).
Like being on a long road trip, these birds frequently stop, rest and refuel on their long migrations. British Columbia acts as a crucial pit stop for Western Sandpipers, during their spring and fall migrations, nearly the entire population passes through the province’s coast. BC’s Fraser River Estuary is a hot spot to see these birds during their migrations (Birds Canada, 2023).
Credit: allaboutbirds.org
FUN FACT: Males outnumber females in the more Northern overwintering areas, while females outnumber males in the more Southern over wintering areas (All About Birds, 2024).
Home is Where the Mud is
Western Sandpipers are most commonly found near the coast, they can be seen roving about areas of low/middle tides, and tidal mudflats. When further inland, they inhabit muddy lakeshores, sewage lagoons, and flooded fields. Western Sandpipers are also known to make a home out of salt pans, evaporation ponds and even abandoned shrimp farms. They prefer their breeding grounds in tundra habitat with dwarf vegetation (All About Birds, 2024).
Credit: Jennifer O’Neill
Behaviour: Feeding & Breeding
You’ll often see these little birds hurrying around in the distance, busying themselves by searching for their next meal (All About Birds, 2024). They’ll often fly away as a collective if you get too close, so bring some binoculars if you want to observe some Western Sandpipers in all their glory.
Western Sandpipers are ground foragers. They’re known to feed on aquatic invertebrates, spiders, insects (Sutherland et al., 2000). They can also sift through biofilm to snack on microbes, diatoms and detritus (Kuwae et al., 2008).
Credit: Ronan Donovan
Western Sandpipers Feeding in a Mudflat
Resembling tiny sewing machines, they feed by repeatedly probing their long bills into soft substrates, like mud or sand, eating whatever their bills run into (Sutherland et al., 2000).
The Breeding Season:
During the breeding season up North, Western Sandpipers don’t pack as densely as they do while in their overwintering habitat. Despite their size, male Western Sandpipers will fiercely defend territories ranging from 0.5-3.5 acres, and will attack any ‘peep’ that dares enter (All About Birds, 2024). These peeps are monogamous and both males and females participate in incubation and chick rearing (Holmes, 1973).
Females choose the nest site and males will prepare the nests. They have 2-4 eggs per clutch, and only one clutch per breeding season. Westerns Sandpipers build their nests out of lichens, willow leaves, and much more (All About Birds, 2024). (Photo credit: Sergey Golubev)
Conservation Status
Thankfully, our friends the Western Sandpipers, fall on the in the ‘Least Concern’ category of the International Unions for Conservation of Nature’s (IUCN) red list. This means that western sandpipers are plentiful in the wild (a whopping ~3.5 million individuals) and are not the focus of conservation efforts, they do not qualify as threatened, near threatened, or conservation-dependent (Canada.ca, 2014).
Credit: fscbiodiverisity.uk
Although their numbers are high, Canada plays a big role in the maintenance of Western Sandpiper populations. British Columbia acts as a migration bottleneck, almost the entire population rests and refuels on BC’s coasts as they travel to and from their breeding grounds. Maintaining Western Sandpiper stopover habitats (ie. intertidal and wetland) will be key to preserving the conservation status of these adorable birds (Canada.ca, 2014).
Research: Altering Migratory Timing to Avoid Predation
Credit: Joshua Stacy
The timing of Western Sandpiper Migration was mostly attributed to food availability at stopover sites, although it may be more complicated than once thought. Since the banning of DDT in the 1970s, (an insecticide that nearly decimated raptor populations) raptor numbers are increasing, including those of the Peregrine Falcon (Falco peregrinus). Peregrine Falcons are an important predator of the Western Sandpiper and since their increase, scientists have noticed altered migratory timing and behaviour in our peeps of interest.
In a data analysis article: Seasonal and inter-annual variation in exposure to peregrines (Falco peregrinus) for southbound western sandpipers (Calidris mauri), researcher Ronald C. Ydenberg compiled 16 years of Western Sandpiper migratory data from the Fraser River Estuary, BC. Ydenberg compared the sandpiper southbound migration behaviour in comparison to the arrival of the Peregrines after their breeding season in the spring.
Ydenberg found that increased exposure to Peregrines during southward migration stopovers correlated with earlier migrations and shorter stopover durations.
Results suggest that Western Sandpipers are actively manipulating migration factors such as: duration and timing to limit risk of predation from Peregrine falcons. This shows Western Sandpipers can display plasticity in their behaviours in order to stay safe, and makes one think about how the conservation of one organism, can affect the behaviours of others.
References:
Archives. “The Western Sandpiper.” Natureweb, 13 July 2022, natureweb.co/western-sandpiper/. Accessed 25 Oct. 2024.
Holmes, Richard T. “SOCIAL BEHAVIOUR of BREEDING WESTERN SANDPIPERS CALIDRIS MAURI.” Ibis, vol. 115, no. 1, 3 Apr. 2008, pp. 107–123, https://doi.org/10.1111/j.1474-919x.1973.tb02627.x. Accessed 29 Apr. 2020.
Sutherland, T. F., et al. “Predation on Meiofaunal and Macrofaunal Invertebrates by Western Sandpipers ( Calidris Mauri ): Evidence for Dual Foraging Modes.” Marine Biology, vol. 137, no. 5-6, 12 Dec. 2000, pp. 983–993, https://doi.org/10.1007/s002270000406. Accessed 11 Sept. 2021.
Tomohiro Kuwae, et al. “BIOFILM GRAZING in a HIGHER VERTEBRATE: THE WESTERN SANDPIPER,CALIDRIS MAURI.” Ecology, vol. 89, no. 3, 1 Mar. 2008, pp. 599–606, https://doi.org/10.1890/07-1442.1. Accessed 13 Oct. 2023.
“Western Sandpiper Overview, All about Birds, Cornell Lab of Ornithology.” Www.allaboutbirds.org, www.allaboutbirds.org/guide/Western_Sandpiper/overview.
Ydenberg, Ronald C. “Seasonal and Inter-Annual Variation in Exposure to Peregrines (Falco Peregrinus) for Southbound Western Sandpipers (Calidris Mauri).” Movement Ecology, vol. 10, no. 1, 27 Oct. 2022, https://doi.org/10.1186/s40462-022-00343-4. Accessed 9 Dec. 2022.
