The term “seagull” is commonly used, but these highly adaptable birds are more accurately called gulls, belonging to the family Laridae. Gulls are a widespread group of medium to large seabirds found globally, often far from the ocean in inland habitats. This guide provides a clear, general description of their physical traits, which are consistent across most common species.
Defining the Archetypal Gull
Gulls exhibit a robust, barrel-chested body structure with a strong, heavy build. Their size varies considerably, ranging from medium-sized species comparable to a pigeon up to much larger species with impressive wingspans. Most gulls have long, pointed wings, perfectly suited for soaring and gliding over water or land with minimal effort.
The classic adult gull plumage follows a pattern of light colors contrasting with darker wings. The head, neck, and underparts are typically a clean, bright white, which helps them blend into bright skies from below. The back and the upper surfaces of the wings, known as the mantle, are usually a shade of pale to medium gray.
A defining feature for many species is the coloration of the outermost primary feathers, or wingtips, which are often black or dark gray. Many of the largest gulls display distinct white spots, sometimes called “mirrors,” on these dark wingtips. These spots provide a subtle but specific visual cue for identification.
Unique Identifying Characteristics
Beyond the general gray-and-white body, the specialized anatomical features of the head and legs are crucial for identification. Gulls possess a stout bill that is generally thick and slightly hooked at the tip. In many of the larger white-headed gulls, the bill is bright yellow and features a distinct red or orange spot near the end of the lower mandible, known as the gonys spot.
The color of the legs and feet is highly variable, ranging from flesh-pink to bright yellow or even a greenish-yellow. All gulls have moderately long legs, allowing them to walk effectively on land. Their feet are fully webbed, which aids in swimming and maneuvering on soft substrates like mud or sand.
Eye color is also quite specific, with some species displaying pale yellow eyes while others have dark, nearly black irises. The eye is often encircled by a thin ring of bare colored skin. Many white-headed gulls also develop dusky streaking or a grayish mask on their heads during the non-breeding winter season, temporarily altering their clean facial appearance.
Plumage Changes: From Juvenile to Adult
A significant challenge in gull identification is the drastic difference between juvenile and adult appearance. Newly fledged gulls, or juveniles, wear a protective plumage that is overwhelmingly mottled brown, streaky, or speckled. This camouflaged look helps them survive their vulnerable first year, as they often lack the clean gray and white of their parents.
The transition to adult plumage is gradual, typically taking two years for smaller species and up to five years for larger gulls. During this time, they pass through several intermediate plumages showing a mix of juvenile brown and emerging adult gray feathers. The back and scapular feathers are usually the first to turn gray, creating a “saddle” of adult color on the mottled body.
Immature gulls are distinct from adults, making identification challenging. Over the course of subsequent molts, the patchy brown gradually gives way to the clean white and gray pattern. The full adult coloration of the bill and legs is often the final trait to fully emerge.