Common Gull vs Ring-billed Gull

In short

The Common Gull (Larus canus) and the Ring-billed Gull (Larus delawarensis) are two distinct gull species that can be differentiated by their size, plumage patterns, and behavioral traits. While both species exhibit similar habitats, the Common Gull typically shows a more uniform gray mantle and darker eye, while the Ring-billed Gull features a distinct black ring around its bill and a more contrasting white head.

Identification tips

1. Birds of the World Similar-Species Diagnostics:

2. The Common Gull (Larus canus) is described as "medium size, similar to L. brachyrhynchus but perhaps slightly heavier and with slightly bigger bill" and generally has a darker eye compared to the Ring-billed Gull (Larus delawarensis). The Ring-billed Gull is noted for its "black ring around its bill," a feature that is not found on the Common Gull.

3. AI Field Diagnostics:

4. When observing these gulls, look for the black ring on the bill of the Ring-billed Gull, which is a definitive identification marker. In contrast, the Common Gull will lack this feature.
5. Check the color of the head: the Common Gull often has a more uniformly gray head, while the Ring-billed Gull has a stark white head with a distinct contrast.
6. Pay attention to group behavior: if you see a larger group of gulls exhibiting aggressive foraging behaviors, it is likely to be Ring-billed Gulls. In contrast, Common Gulls tend to congregate in smaller groups and are less aggressive.
7. Observe their flight style: Ring-billed Gulls are often seen flying in larger flocks and are more likely to engage in aerial displays compared to the Common Gull.

By focusing on these key distinguishing features, birdwatchers can effectively differentiate between the Common Gull and the Ring-billed Gull in the field.

Size

• Common Gull: Medium-sized, generally heavier than the Ring-billed Gull, with a length of approximately 40-45 cm (15.7-17.7 inches) and a wingspan of 100-110 cm (39-43 inches).
• Ring-billed Gull: Slightly smaller, measuring around 40-43 cm (15.7-16.9 inches) in length and a wingspan of 110-120 cm (43-47 inches).

Plumage

• Common Gull: Adult plumage features a medium to pale gray mantle, with black extending near the tips of primary coverts. The head is generally more uniformly colored with less variation in markings, especially in the breeding season. The eyes are dark, often appearing darker than those of the Ring-billed Gull.
• Ring-billed Gull: Characterized by a notable black ring around its bill, which is a key identifying trait. The mantle is also gray but typically has a more pronounced contrast with the white head, especially in adult birds. They may show a more extensive white spot between the gray and black on the primaries.

Behaviour

• Common Gull: Often seen in smaller groups, and displays less aggressive behavior compared to the Ring-billed Gull. They tend to forage in open fields and near water, often scavenging.
• Ring-billed Gull: More social and often found in larger groups, especially in urban areas. They exhibit aggressive foraging behavior and are known to steal food from each other and other birds.

Habitat

• Common Gull: Prefers coastal areas, freshwater lakes, and wetlands. In Europe, they nest in colonies on islands or near water bodies, often influenced by ice age geology.
• Ring-billed Gull: Commonly found in a variety of habitats including coastal areas, lakes, rivers, and urban environments. They nest on the ground in colonies, often near water bodies.

Voice

• Common Gull: Vocalizations include a series of sharp, high-pitched calls, often described as "kreee."
• Ring-billed Gull: Their call is a distinctive, low-pitched "kaw," and they are known for a more varied vocal repertoire compared to the Common Gull.