The term “seagull” is a common name used to describe species belonging to the family Laridae, which are correctly referred to as gulls. No single species is actually named “seagull,” and many gulls are found far from the ocean in inland habitats like lakes, rivers, and landfills. This generalized name is often applied to various white and gray water birds that share a similar build and have adapted to scavenging near water. This visual uniformity is why distinct species are frequently confused with gulls.
The Primary Lookalike: Terns
Terns are the most common group of birds mistaken for gulls, belonging to the same biological order, Charadriiformes, and often sharing coastal areas. Gulls have a stout body and broad, rounded wings, while terns possess a streamlined body and long, narrow, pointed wings. This difference gives terns a more graceful, buoyant flight compared to gulls’ steadier gliding.
The bill structure is a key difference. Gulls generally have a thick, stout bill with a hooked tip, aiding in opportunistic feeding. Terns have a delicate, sharply pointed bill adapted for spearing small fish. Most tern species also feature a deeply forked tail, whereas gulls typically have a fan-shaped or slightly notched tail.
Their feeding behavior provides the most dramatic contrast. Terns are plunge-divers that hover and dive headfirst to catch fish. Gulls rarely dive, preferring to pick up items from the water surface or the ground. Terns are fish-eaters, while gulls are adaptable, omnivorous feeders that consume fish, invertebrates, carrion, and human scraps.
Distinguishing Gulls from Jaegers and Skuas
Jaegers and Skuas, belonging to the family Stercorariidae, are often confused with gulls, especially offshore. These birds are highly predatory and exhibit different behavior and appearance. They often have darker, brownish plumage compared to the light-gray and white coloration of most gulls.
Their feeding strategy is distinctly different, as Jaegers and Skuas are notorious for kleptoparasitism. They aggressively chase other seabirds, including gulls and terns, forcing them to drop or regurgitate their catch. This high-speed pursuit is a defining behavioral trait not commonly seen in gulls.
A noticeable physical characteristic is the structure of their tail feathers. Breeding adults of smaller Jaeger species have two central tail feathers that are elongated and pointed, projecting beyond the rest of the tail. Although they may have a similar hooked bill to some gulls, their long, pointed wings and robust appearance distinguish them.
Actionable Identification Markers
When identifying a gull-like bird, focusing on specific details can quickly narrow down the possibilities. The color of a bird’s legs is a helpful field mark: large gulls often have pink legs, medium-sized gulls frequently have yellow legs, and smaller gulls may display black or red legs. This color serves as a good initial sorting tool, though it can change slightly with age or season.
Observing the size of the bird relative to known objects provides an important clue, as gulls range from the dove-sized Little Gull to the massive Great Black-backed Gull. The color of the mantle, or back feathers, is also significant. Slight variations in the shade of gray help differentiate species, such as the pale-backed Herring Gull from the darker-backed Lesser Black-backed Gull.
Specific markings on the head and wings also aid identification. Examples include the distinct black ring on the bill of an adult Ring-billed Gull. Many gulls show white patches, known as “mirrors,” on their dark wingtips, and the size and placement of these mirrors are species-specific features. Paying attention to whether the bird has a white head, a dark “hood,” or a streaky head pattern is also useful, as these change between breeding and non-breeding seasons.