The Western Gull is a large, robust gull commonly found along the Pacific coast of North America, including all of Oregon's coastline. They are a prominent resident species and are often the most dominant gull in coastal areas. It's important to note that in the Pacific Northwest, Western Gulls frequently hybridize with Glaucous-winged Gulls, creating a "hybrid swarm" that can make identification challenging, as these hybrids (sometimes called "Olympic Gulls") exhibit a range of intermediate features. However, we'll focus on the pure Western Gull here.

Overall Characteristics of Western Gulls:
Size & Build: Large, heavy-bodied gull with a powerful appearance. They have a thick neck, a large head, and a very heavy, bulbous-tipped yellow bill. Their legs are **pink**. They have broad wings.
Bill: Heavy, yellow, with a prominent **red spot** on the lower mandible near the tip (the "gonys spot").
Legs: Pink, often a key differentiator from yellow-legged gulls.
Eyes: In the northern subspecies ($L. o. \text{ occidentalis}$) found in Oregon, the eyes are typically dark brown or olive-yellow, contrasting with the paler eyes of some other large gulls. They have an orange-red orbital (eye) ring.
Flight: Powerful and direct. In flight, their **dark slaty-gray back and upperwings** are distinctive. The wingtips are black (or very dark gray), blending gradually into the darker back, and have small white "mirrors" (spots) on the outer primaries. They typically show a narrow white trailing edge to the wing.
Voice: A deep, loud, sometimes whistly "keow" or "klee-ooh."

Plumage - Very Similar for Male and Female, but varies significantly by age and season:
1. Breeding (Alternate) Plumage (Adult, seen in Oregon during spring and summer):
Head: Pure white head and neck, with very little to no streaking.
Body: Dark slaty-gray back and upperwings (mantle), clean white underparts.
Bill: Bright yellow with a prominent red gonys spot.
Legs: Pink.
Eyes: Dark, with a reddish-orange orbital ring.

2. Non-breeding (Basic) Plumage (Adult, most common in Oregon from late summer through winter):
Head: The head and neck remain largely white, but may show **very minimal, faint dusky streaking** on the crown, nape, and around the eye. This streaking is typically much less extensive than in many other gull species in non-breeding plumage.
Body: Dark slaty-gray back and upperwings, white underparts, similar to breeding plumage.
Bill: Duller yellow, and the red gonys spot might be less vibrant.
Legs: Pink.

3. Juvenile Plumage (seen in Oregon from late summer into fall/winter, often remaining through their first year):
Overall: Heavily mottled in sooty-browns and grays, giving a "dirty" or "messy" appearance.
Upperparts: The head, neck, and underparts are dark brown or dusky, often appearing mottled or streaked.
Wings: Dark brown or blackish primaries and secondaries, often with pale barring on the tail and rump.
Bill: Entirely blackish.
Legs: Grayish-pink.
Western Gulls take approximately four years to reach full adult plumage, so you will see a variety of intermediate plumages (first-winter, second-winter, third-winter) which gradually lose their brown mottling, gain adult gray plumage, and their bills and legs transition to adult colors.

Distinguishing Male from Female:
Like most large gull species, **male and female Western Gulls have virtually identical plumage and coloration in all plumages and seasons.** There are no specific feather patterns or colors that reliably allow for sex determination in the field.

However, there is a noticeable and often discernible difference in size and structure:

Males are generally larger and heavier than females. This can be quite significant, with males being 15-20% larger and having noticeably larger heads and thicker, more robust bills with a more pronounced gonydeal (lower mandible) angle.
This difference is most apparent when observing a breeding pair together, where the male will clearly appear the more imposing individual. When observing single birds, it can be harder to be certain without a direct comparison, but very large individuals are likely males, and smaller individuals are likely females.

Therefore, for practical field identification of Western Gulls in Oregon, you will focus on the age and seasonal plumage, the diagnostic dark slaty-gray mantle, pink legs, heavy yellow bill with a red spot, and the overall large, powerful structure. When trying to differentiate sexes, look for noticeable size differences between individuals, especially in pairs.