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LEAST SANDPIPER  Calidris minutilla 13–14cm. Commonest, most wide­

spread small migrant sandpiper in Costa Rica, found in varied habitats from

small roadside ponds and lakeshores to tidal mudflats, coastal lagoons, sewage

ponds; less often open beaches and rocky coasts, mainly when roosting. Often

in flocks, locally of 100s, mixing readily with other small sandpipers but often

keeps to drier and more vegetated habitats than Western Sandpiper. Feeds by

picking and probing; creeps along muddy shores with flexed legs. Best identified

by rather mouse-like demeanor, overall brownish plumage with white belly,

medium-length decurved bill; yellowish legs often muddy. Western and

Semipalmated Sandpipers are larger and whiter-breasted, walk and run with more upright gait, favor

more open habitats, often wade in open water. SOUNDS: High, reedy, rolled krreep and lower krriit; varied

low trilling. STATUS: Fairly common to common Aug–May, mainly below 1500m; more widespread in

migration. (Breeds N America, winters to n. S America.)

SEMIPALMATED SANDPIPER  Calidris pusilla 14–15cm. Small, rather com­

pact migrant sandpiper with short to medium-length straightish bill, dark legs;

structure suggests a mini-Sanderling. Coastal lagoons, salt ponds, mudflats,

river mouths, beaches. Feeds by probing and picking. From Western Sandpiper

by structure, especially shorter, blunter-tipped bill (some female Semipalmated

have longer bill, overlapping short-billed male Western); juv. more uniform

above (vs. grayish with rusty scapulars) than juv. Western; nonbr. slightly darker

above, more brownish gray. Cf. Least and other small sandpipers. SOUNDS: Fairly

sharp kyip, lower chrit; nasal twitters from feeding flocks. STATUS:  Fairly

common to common Aug–Oct, Mar–May on Pacific coast, smaller numbers on Caribbean coast and

inland; uncommon to fairly common in winter in Gulf of Nicoya. (Breeds N America, winters Mexico to

S America.)

WESTERN SANDPIPER  Calidris mauri 15–16.5cm. Small, rather long-necked

migrant sandpiper with relatively long, slightly decurved and tapered bill, black

legs. Coastal lagoons, mudflats, salt ponds, river mouths, beaches, lakeshores.

Feeds by probing and picking, often wading up to its belly in water. Note bright

rusty tones on juv. and breeding plumages; cf. Semipalmated and Least

Sandpipers. SOUNDS: High, scratchy, downslurred chiit, burry chrrit; wheezy

twitters from feeding flocks. STATUS: Fairly common to common Aug–May on

Pacific coast, especially Gulf of Nicoya, small numbers oversummer locally;

uncommon to fairly common on Caribbean coast; rare inland during migration.

(Breeds N America, winters to n. S America.)

WHITE-RUMPED SANDPIPER  Calidris fuscicollis 17–18.5cm. Small, very

long-winged transient migrant sandpiper of varied wetland habitats, from

mudflats and lakeshores to river mouths, flooded fields. Singles or small groups,

mixing readily with other small sandpipers. Feeds by picking, less often probing,

often while wading in shallow water. Note long wings projecting past tail tip,

lack of buffy plumage tones, variable pink base to mandible, voice; white

uppertail coverts distinctive in flight. Cf. Baird’s, Semipalmated, and Western

Sandpipers. SOUNDS: Very high, slightly tinny, descending jit, easily missed or

passed off as a songbird. STATUS: Scarce to uncommon Sep–Nov, Apr–May on

both slopes, mainly in coastal lowlands. (Breeds N America, winters S America.)

BAIRD’S SANDPIPER  Calidris bairdii 16.5–18cm. Small, very long-winged

transient migrant sandpiper of inland and coastal habitats, from wetlands and

volcano lakes to grassy marshes, coastal lagoons, rarely open beaches and

mudflats. Singles or groups, mixing readily with other sandpipers. Feeds by

picking, less often probing, regularly in fairly dry habitats away from water.

Note long wings projecting past tail tip, buffy plumage, dark legs, rather fine

bill, voice. Cf. White-rumped and Pectoral Sandpipers. SOUNDS: Dry trilled

krrih, higher and drier than Pectoral Sandpiper. STATUS: Uncommon, mainly

Sep–Oct, Mar–May through interior, to 3000m; scarce on Pacific coast, rare on

Caribbean coast. (Breeds N America, winters S America.)