The Least Sandpiper is North America’s smallest shorebird, measuring just 5–6 inches in length and weighing under an ounce. In Arizona, it is primarily a spring and fall migrant, arriving in March–May and again in July–October, with peak numbers staged at desert wetlands, irrigation ponds and mudflats. Look for them probing shallow edges at sites such as the Bill Williams River National Wildlife Refuge, Cibola and Mittry Lake wildlife areas along the Lower Colorado River, and the wastewater treatment ponds around Phoenix and Yuma. In non-breeding plumage, they show dull brown-gray upperparts, clean white underparts with pale buff breast wash, fine dark streaking, and distinctive bright yellow-green legs; breeding birds sport richer rufous tones on the back and crown. Least Sandpipers feed by gleaning small invertebrates from substrate, often rapidly “pattering” at the water’s edge. Although most depart by late October, a few linger through mild winters in riparian marshes and farm reservoirs.
