The Lesser Yellowlegs is about half the size (in weight) of the Greater Yellowlegs, which is a useful distinction when the two are seen together. Listen For Voice is the best way to tell these birds apart. The greater yellowlegs (Tringa melanoleuca) is a large North American shorebird.The genus name Tringa is the New Latin name given to the green sandpiper by Aldrovandus in 1599 based on Ancient Greek trungas, a thrush-sized, white-rumped, tail-bobbing wading bird mentioned by Aristotle.The specific melanoleuca is from Ancient Greek melas, "black", and leukos, "white".

Its bill is long and fairly thick for a shorebird, and its legs are gray. The Willet is a large, chunky shorebird with drab plumage. The Willets closest relative is the Lesser Yellowlegs, a much smaller bird with a very different appearance apart from the fine, clear and dense pattern of the neck which both species show in breeding plumage. These long-legged, straight-billed shorebirds feed along beaches, mudflats, and rocky shores.
Look For Greater yellowlegs are larger than lesser yellowlegs, but size can be hard to judge unless both species are side by side.

Willet definition is - a large American shorebird (Catoptrophorus semipalmatus) of the sandpiper family that resembles the greater yellowlegs but has a thicker bill and gray legs and that displays a black-and-white wing pattern when in flight. It tends to be more heavily barred than the lesser and tends to be loner.

It differs from the lesser yellowlegs by it size (14 inches compared to 10 1/2 inches) and by its longer bill (about… That is one big, lanky, pale willet.
Greater Yellowlegs have a bill that is about twice the length of its head, and sometimes shows a slight upward curve. Two distinct populations inhabit North America, one nesting in prairie marshes, the other in salt marshes along the Atlantic and Gulf Coasts. Genus Calidris (the “peeps”) A Willet standing on the beach is simply a large plain shorebird; but its identity is obvious as soon as it spreads its wings, and it even calls its name in flight. Greater Yellowlegs As you have already guessed, “yellow legs” are a distinguishing feature of this long-billed shorebird. Piercing calls and distinctive wing markings make the otherwise subdued Willet one of our most conspicuous large shorebirds. A different angle of the bill. It is similar in height to a Greater Yellowlegs, but heavier and with a shorter neck. Willets and yellowlegs are birds similar in appearance, as are the greater and lesser yellow legs. It is mottled gray all over, with heavier barring in breeding plumage than in winter. Both have long, bright yellow legs. Similar looking birds to Willet: Greater Yellowlegs Breeding adult, American Avocet Breeding adult, Marbled Godwit Breeding adult, Whimbrel Adult (Hudsonian) Lessers appear delicate in every way, including the all-dark needle-thin bill. The bill of the Lesser Yellowlegs is not significantly longer than the diameter of its head, whereas the Greater Yellowlegs' bill is much longer.

Note the long legs, size much larger than the adjacent Greater Yellowlegs, bill shape, grayish coloration, and the degree of contrast between the scaps and coverts. Willet definition is - a large American shorebird (Catoptrophorus semipalmatus) of the sandpiper family that resembles the greater yellowlegs but has a thicker bill and gray legs and that displays a black-and-white wing pattern when in flight.