Gull-billed Tern vs Caspian Tern

In short

The Gull-billed Tern and Caspian Tern can be distinguished primarily by their bill shape and size. The Gull-billed Tern has a shorter, thicker black bill, while the Caspian Tern features a larger, more robust red bill. Additionally, the Caspian Tern is notably larger overall.

Identification tips

1. Bill Shape: Look for the Gull-billed Tern's short, thick black bill versus the Caspian Tern's large, robust red bill. 2. Size: Note the Caspian Tern's larger size and broader wingspan. 3. Plumage: During breeding, the Caspian Tern has a more extensive black cap and a white forehead in non-breeding plumage. 4. Behavior: Observe foraging behavior; Caspian Terns plunge-dive for fish, while Gull-billed Terns hawk insects. 5. Vocalization: Listen for the Caspian Tern's loud, harsh calls compared to the softer calls of the Gull-billed Tern.

Size

The Caspian Tern is the largest tern species, significantly larger than the medium-sized Gull-billed Tern.

Plumage

Both species have pale gray upperparts and white underparts, but the Caspian Tern has a more extensive black cap during breeding season and a distinctive white forehead in non-breeding plumage. The Gull-billed Tern's black cap is less extensive, and it often appears whiter-headed in non-breeding plumage.

Behaviour

Caspian Terns are known for their dramatic, gull-like soaring and plunge-diving for fish, while Gull-billed Terns tend to hawk insects and are less likely to dive.

Habitat

Caspian Terns are found along coastlines and large inland water bodies, often nesting on flat, open areas. Gull-billed Terns prefer coastal marshes and inland wetlands, often foraging over fields and mudflats.

Voice

The Caspian Tern has a loud, raucous call, often described as a harsh 'kree' or 'kraa', while the Gull-billed Tern's call is softer and less distinctive.