Great Black-backed Gull vs Slaty-backed Gull

In short

The Great Black-backed Gull and Slaty-backed Gull are large gulls with overlapping ranges, especially in North America. The Great Black-backed Gull is the largest gull species, while the Slaty-backed Gull is slightly smaller with distinct plumage differences. Key identification features include size, mantle color, and wing pattern.

Identification tips

1. Size: Look for the larger size and bulk of the Great Black-backed Gull. 2. Mantle Color: Note the darker back of the Great Black-backed Gull compared to the slate-gray of the Slaty-backed Gull. 3. Wing Pattern: Check for white 'mirrors' on the Slaty-backed Gull's wingtips. 4. Location: Consider the geographic range; Great Black-backed Gulls are more common in the North Atlantic, while Slaty-backed Gulls are more frequent in the North Pacific.

Size

The Great Black-backed Gull is notably larger and bulkier than the Slaty-backed Gull, making it the largest gull species.

Plumage

The Great Black-backed Gull has a very dark, almost black back and wings, while the Slaty-backed Gull has a slightly lighter slate-gray back. The Slaty-backed Gull also has distinctive white 'mirrors' on the tips of its primary feathers.

Behaviour

Both species are opportunistic feeders, often seen scavenging near human activity, but the Great Black-backed Gull is more aggressive and dominant in mixed flocks.

Habitat

Both species are found near coastal areas, but the Great Black-backed Gull is more commonly seen in the North Atlantic, while the Slaty-backed Gull is more prevalent in the North Pacific.

Voice

Vocalizations are similar, with typical gull-like calls, but specific differences are not well-documented.