Greater Yellowlegs are prominent and vocal shorebirds that are common migrants through Oregon's wetlands, estuaries, and mudflats. While they are a joy to observe with their striking yellow legs and distinctive calls, telling the difference between males and females in the field is extremely challenging, as they exhibit very little to no sexual dimorphism in their plumage.

General Appearance of Adult Greater Yellowlegs (both sexes):
Size and Shape: They are large, lanky shorebirds, notably larger than their cousin, the Lesser Yellowlegs. They stand tall with very long, bright yellow legs (hence the name), a long neck, and a relatively small head. Their bill is long, slender, and often appears slightly upturned, with a dark tip and sometimes a paler base.
Plumage (Non-breeding/Migration through Oregon):
Upperparts: Mottled gray or grayish-brown on the back and wings, often with fine whitish speckling, giving a "salt and pepper" appearance.
Underparts: Clean white belly.
Breast and Neck: The neck and breast are finely streaked with dusky gray.
Face: They have a prominent white eye-ring and a subtle pale supercilium (eyebrow stripe).
Plumage (Breeding - less likely to see in Oregon, as they breed further north):
In breeding plumage (which some individuals may still show early in spring migration or late in fall migration), the streaking on the head, neck, and breast becomes denser and darker, sometimes appearing as more defined barring. The flanks may also show heavier dark barring.
Tail: In flight, a key identifying feature is their white tail, which is barred with black, particularly on the outer feathers. Their underwings are dark, contrasting with the white belly.
Behavior: They typically walk with a purposeful, high-stepping gait across mudflats and shallow water. They often bob the front half of their body or head. They are quite wary and are often the first birds to sound an alarm, with their loud, piercing calls.

Plumage: The feather patterns and coloration are virtually identical for both sexes, in all plumages. There are no consistent differences in the intensity of streaks, barring, or overall coloration that reliably indicate sex.
Size: While scientific studies suggest that females may average slightly larger and heavier than males, this difference is usually too subtle to be discerned reliably in the field without direct comparison or measurements. There's significant overlap in individual sizes between the sexes.

Vocalizations: Both sexes give the characteristic loud, ringing, three or four-note "tew-tew-tew" or "chew-chew-chew" calls, which is a primary identification feature for the species. There are no commonly reported vocal differences that reliably distinguish males from females.
Courtship Displays (Breeding grounds): On their breeding grounds, males perform elaborate aerial displays, with coasting dives and insistent whistled songs, to attract females. They may also land and run in circles around a female with upraised wings. These behaviors are not typically observed in Oregon, where they are primarily migrants.
Incubation and Parental Care (Breeding grounds): Both parents share incubation duties and care for the young.