The greater yellowlegs is a medium-sized shorebird belonging to the genus Tringa in the family Scolopacidae. It breeds in northern North America and winters along the Atlantic and Pacific coasts of North America, Central America, the Caribbean, and South America. Two subspecies are recognized: T. m. melanoleuca breeds in eastern and central Canada and winters along the Atlantic coast, while T. m. gambeli breeds in Alaska and winters along the Pacific coast.
The greater yellowlegs is a slate gray bird with long yellow legs and a long, slightly upturned bill. It is similar in appearance to the smaller, more common lesser yellowlegs. Some key identification features of the greater yellowlegs include its larger size, louder three-note call, and more deliberate feeding action compared to the nimble lesser yellowlegs.
Habitat
During the breeding season, greater yellowlegs inhabit open wetlands in boreal forests, muskegs, and wet tundra. They nest near ponds, lakes, streams, and bogs, often on hummocks or grass tussocks. On migration and in winter, greater yellowlegs frequent marshes, mudflats, flooded fields, and estuaries. They roost on sandbars and beaches when suitable.
Food and Feeding
Greater yellowlegs forage by wading in shallow water and probing with their long bills. They are carnivorous, eating insects, small fish, frogs, tadpoles, and crustaceans. They will also consume aquatic plants and seeds. Greater yellowlegs scan for prey visually while standing still or walking steadily through the water. Upon spotting food, they will rapidly stab at it with their bill.
Breeding
Greater yellowlegs breed from early May to July across Canada and Alaska. They are monogamous and thought to mate for life, pairing up on breeding grounds soon after arrival. The nest is a shallow scrape lined with leaves, lichens, twigs, and grass, built on dry ground near water. The female lays 3-5 eggs that are incubated by both parents for 22-24 days. The downy precocial chicks leave the nest within a day and are tended by the male parent. The chicks fledge after 20-25 days, when they are able to fly. Pairs may re-nest if the first clutch fails.
Migration
Greater yellowlegs undertake long annual migrations between their northern breeding grounds and wintering areas extending from the southern U.S. to southern South America. They migrate at night in loose flocks; nocturnal migration might help avoid some diurnal predators. Their migrations appear to follow flyways over land rather than shortest possible coastal routes. Greater yellowlegs can migrate long distances; banded birds have been recovered over 4,000 km from banding sites. Spring migration occurs March-May, and fall migration is July-October.
Behavior
Roosting
Greater yellowlegs roost communally in shallow water or on sandbars and beaches during the non-breeding season. They show high fidelity to roost sites. Radio-tracking data show that greater yellowlegs may use separate night roosts and daytime foraging sites, traveling up to 19 km between them daily. Social interactions at roosts might help yellowlegs find productive feeding sites.
Territoriality
On the breeding grounds, male greater yellowlegs establish and defend territories with threat displays and aerial chases. Territories contain nesting and foraging areas, maintained through the nesting cycle. Males perform flight displays advertising territory ownership and fitness to females. Aggressive territorial defense ensures spacing between nests and access to food resources.
Parental Care
Greater yellowlegs exhibit a division of parental duties during breeding. Males tend the precocial chicks once they hatch, leading them to suitable foraging areas. Females continue incubating any remaining eggs in the nest before leaving to join the male and fledglings. Parents protect young with alarm calls and distraction displays like injury feigning. Chicks fledge and become independent of parents approximately 3 weeks after hatching.
Flocking Behavior
During migration and winter, greater yellowlegs gather in loose flocks, sometimes associating with other shorebirds. Flocks likely form for predator detection, social information sharing, and possibly aerodynamic advantages. Radio-tracking shows wintering birds often follow regular daily patterns traveling between roosting sites, foraging grounds, and loafing sites.
Population and Conservation
Population Trends
North American Breeding Bird Survey (BBS) data from 1966-2019 show greater yellowlegs populations are remaining stable rangewide over the long-term, with a slight increasing trend of 0.18% per year. However, trends vary regionally, with significant declines seen in some eastern survey regions. Christmas Bird Count data also show no obvious population trends during winter.
Major Threats
As a widely dispersed migratory species, greater yellowlegs face threats on their breeding and non-breeding grounds and migration routes. Habitat loss and degradation from wetland drainage, pollution, development, and resource extraction impact their populations. Increased predation from cats, foxes, gulls, and raptors near human settlement is a threat. Collisions with structures and vehicles can cause mortality during migration. Disturbance from human recreation disrupts nesting and roosting birds.
Conservation Status
The global greater yellowlegs population is estimated at 730,000 birds. Numbers appear to be stabilizing following population declines from hunting and wetland loss in the late 19th and early 20th centuries. They are considered a species of Least Concern on the IUCN Red List due to their extensive range and population size. Partners in Flight estimates a global breeding population of 310,000. They are protected under the Migratory Bird Treaty Act in the U.S. and Canada.
Comparison to Lesser Yellowlegs
The greater yellowlegs is often found alongside its smaller relative, the lesser yellowlegs. Here is a table comparing some key attributes of both species:
Species | Length | Wingspan | Bill Length | Weight | Breeding Range |
---|---|---|---|---|---|
Greater Yellowlegs | 14 inches | 25 inches | 3 inches | 7.4 ounces | Central Canada, Alaska |
Lesser Yellowlegs | 10.5 inches | 21 inches | 1.75 inches | 3.2 ounces | Western and Central Canada |
As shown in the table, the greater yellowlegs is noticeably larger with a proportionally longer bill and greater body mass. Its breeding range extends farther north and east into the boreal forests and tundra habitats. Overall, the greater yellowlegs is less common and more solitary compared to the abundant and gregarious lesser yellowlegs.
Conclusion
In summary, the greater yellowlegs is a charismatic shorebird known for its rangy size, loud vocalizations, and dashing elegant looks. It inhabits wide-open wetland habitats across northern North America during breeding season, migrating long distances to winter along both coasts. Though sociable at times, it fiercely defends breeding territories and exhibits remarkable dedication and teamwork as parents. Greater yellowlegs populations appear to be holding steady amidst threats from human disturbance and habitat degradation. Sustained conservation focus on protecting wetlands across their range will help ensure the future of these iconic shorebirds. While they may be distinguished from their lesser cousins by subtle features, greater yellowlegs remain emblematic shorebirds on their own merit. Their graceful movements and sprightly manner will continue inspiring birdwatchers and biologists tracking their yearly travels across the continent.