The Lesser Yellowlegs (Tringa flavipes) is a medium-sized shorebird that breeds in boreal forests across Canada and Alaska and winters along the coastlines of North America, Central America, the Caribbean, and South America. Known for its bright yellow legs and rapid, erratic feeding behavior, the Lesser Yellowlegs is a common sight in wetlands, tidal flats, flooded fields, and shorelines during migration and in winter. In this article, we will cover the identification, range, habitat, diet, behavior, breeding, and conservation status of this elegant shorebird.
How to Identify the Lesser Yellowlegs
With their thin, upright bodies, long legs, and long, thin bills, yellowlegs are unmistakable shorebirds. Within the genus, the aptly named Lesser Yellowlegs is the smaller of the two yellowlegs species. Adults measure 8-10 inches in length and weigh 2-3 ounces. Compared to the similar Greater Yellowlegs, the Lesser Yellowlegs has a smaller and more delicate frame, a shorter neck and bill, and yellow rather than yellow-green legs.
The breeding adult Lesser Yellowlegs has grayish-brown upperparts with white spots on the back and wings. The underparts are white with faint gray-brown barring on the flanks and undertail coverts. The tail is barred with black and white. There is a white stripe over the eye. Non-breeding adults have paler, more muted upperparts. Juveniles resemble non-breeding adults but with yellowish legs and diffuse streaking on the breast. In flight, look for the white rump patch and tail pattern.
Relative to body size, Lesser Yellowlegs have the longest legs of any North American shorebird. In flight, their toes project clearly beyond the tip of the tail. The legs and feet are bright yellow in adults. The thin bill is dark with a pale yellowish base.
Lesser Yellowlegs often forage in small flocks. Listen for their distinctive flight call, a descending, plaintive whistle (“tu-tu-tu”). The call is faster and higher-pitched than the similar call of the Greater Yellowlegs.
Range and Habitat
The Lesser Yellowlegs breeds across northern boreal forests in Canada and Alaska. They nest in open bogs, muskeg, wet tundra, and the damp margins of lakes and ponds.
During migration, Lesser Yellowlegs stop over at freshwater and brackish wetlands across North America. They winter along both the Atlantic and Pacific coasts from Mexico south to Chile and Argentina. On the Atlantic Coast, they primarily winter from the southeast U.S. south into the Caribbean and along the northern coast of South America. Along the Pacific, they are found from Mexico south to Ecuador.
During the nonbreeding season, look for Lesser Yellowlegs around shallow lakes, ponds, marshes, estuaries, tidal mudflats, flooded fields, and shorelines. They prefer habitats with soft muddy or sandy substrates where they can easily probe for invertebrates. Compared to other shorebirds, Lesser Yellowlegs more frequently forage in freshwater habitats.
Diet
Lesser Yellowlegs forage by sight, walking slowly through the water and scanning for prey. They have a rapid, sewing machine-like feeding motion as they pick small food items from the surface or probe into mud or sand. Their diet consists primarily of small aquatic invertebrates including insects, crustaceans, worms, mollusks, and other invertebrates. Common prey items include midges, beetles, dragonflies, damselflies, aquatic worms, shrimp, and small snails.
During the breeding season, the diet consists more of terrestrial invertebrates with aquatic insects still making up a substantial proportion. Foraging areas include the muddy shores of ponds, flooded tundra, muskeg, and damp meadows. On the wintering grounds, Lesser Yellowlegs forage almost exclusively on estuarine and marine invertebrates in coastal habitats.
Behavior
During the nonbreeding season, Lesser Yellowlegs are migratory and winter in flocks along coastlines. During migration, they stopover in large, loose flocks that concentrate where food resources are abundant. Flocks wheel and turn erratically in flight when flushed.
On the breeding grounds, Lesser Yellowlegs are aggressive and territorial. They have elaborate aerial displays including steep dives and rapid zig-zag flights. Males perform display flights and chase other males away. They are monogamous and both sexes defend the nesting territory.
Lesser Yellowlegs frequently nod while feeding. They are active day and night on their wintering grounds but primarily diurnal during the breeding season. While foraging, they are wary and frequently pause with an erect posture to survey their surroundings. They may forage in shallow water by submerging their heads and walking in a circle to stir up prey.
To conserve heat, Lesser Yellowlegs stand on one leg while resting. They are more heat tolerant than many other shorebirds and actively forage on inland and coastal sites during the hottest part of the day.
Breeding
Lesser Yellowlegs arrive on the breeding grounds in May and June. The nest is a shallow scrape lined with leaves, lichens, and grasses and built on dry hummocks or tussocks in open bogs and wet tundra. The female lays a clutch of 3 to 5 eggs that are buff to olive in color with brown spotting. The breeding pair both incubate the eggs for 21-22 days until hatching.
The precocial young leave the nest within a day and are brooded by the male while the female continues to incubate any remaining eggs. The young fledge at about 18-20 days old. By 3 weeks, they are independent and capable of sustained flight. The female often deserts the brood and initiates fall migration before the young have fledged.
Breeding densities are low with nests dispersed at intervals of hundreds of yards or more. Lesser Yellowlegs exhibit site fidelity and return to the same nesting sites year after year. The male performs display flights over the nesting territory until the young have fledged and sometimes beyond.
Migration
Lesser Yellowlegs undertake long distance migrations between their boreal breeding grounds and wintering areas that may be thousands of miles apart. They fly non-stop over large ecological barriers like the Gulf of Mexico and Caribbean Sea that cannot provide rest stopovers.
Southbound migration begins in late summer and early fall as adults and juveniles move south from the breeding grounds. Peak fall passage occurs from mid-August through September. Northbound return migration occurs in April and May.
Migrating and wintering Lesser Yellowlegs concentrate along coastlines where marine invertebrates are abundant. On the Atlantic Coast, they primarily winter from the Carolinas south into the Caribbean, Mexico, and Central America. On the Pacific Coast, they winter from Baja California to South America.
Lesser Yellowlegs make frequent stopovers to rest and feed during migration. Major stopover regions include the Central Valley of California, Cheasapeake Bay, coastal Louisiana, Texas Coastal Bend, and areas along the Mississippi River.
Conservation Status
Lesser Yellowlegs are still common and widespread. However they face threats on their breeding and wintering grounds as well as migratory stopover sites. The primary threats include:
- Habitat loss and degradation due to development, pollution, and sea level rise
- Disturbance from human recreation and development
- Collision mortality from structures and vehicles
Lesser Yellowlegs are protected under the Migratory Bird Treaty Act in the U.S. and Canada. Population trends are decreasing but the species is still considered to be of Least Concern by the IUCN Red List. Ongoing conservation efforts should protect key migratory stopover sites and wintering coastal wetlands throughout their range.
Conclusion
With their brightly colored legs, erratic flight, and piercing whistle, the Lesser Yellowlegs is a distinctive shorebird that thrives across a range of North American wetland habitats. Their specialized bill allows them to capture small aquatic and terrestrial invertebrates with speed and precision. While Lesser Yellowlegs still number in the hundreds of thousands, habitat loss and degradation pose increasing threats to populations. Ongoing conservation efforts focused on protecting wetlands across their breeding and nonbreeding ranges will help ensure these elegant shorebirds remain a thriving species.