Forster's Tern vs Common Tern

In short

Forster's Tern and Common Tern can be distinguished by their tail length and plumage details. Forster's Tern has a longer tail with a more deeply forked appearance, while the Common Tern has a shorter, less forked tail. In breeding plumage, Forster's Tern shows a whiter body and a paler gray upperwing compared to the Common Tern.

Identification tips

• Tail length and fork: Forster's Tern has a longer, more deeply forked tail.
• Breeding plumage: Look for the whiter body and paler gray upperwings in Forster's Tern.
• Non-breeding plumage: Forster's Tern shows a black eye patch, while Common Tern's head is more uniformly gray.
• Habitat: Check the surrounding habitat; Forster's Tern prefers marshes, while Common Tern is more coastal.
• Vocalizations: Listen for softer calls in Forster's Tern compared to the harsher calls of the Common Tern.

Size

Both species are similar in size, but Forster's Tern may appear slightly more slender.

Plumage

In breeding plumage, Forster's Tern has a whiter body and paler gray upperwings compared to the Common Tern, which has a darker gray body and wings. Forster's Tern also has a more pronounced black cap and a longer, more deeply forked tail. In non-breeding plumage, Forster's Tern shows a distinctive black eye patch, while the Common Tern's head is more uniformly gray.

Behaviour

Both species exhibit similar foraging behaviors, diving for fish from the air. However, Forster's Tern is more often associated with marshes, while Common Tern is frequently found along coasts and larger bodies of water.

Habitat

Forster's Tern is primarily a marsh bird, often found in fresh, brackish, and saltwater marshes. Common Tern, on the other hand, is more coastal, breeding on sandy or rocky islands and shores.

Voice

Vocalizations are similar, but Forster's Tern's calls are generally softer and less harsh compared to the Common Tern's more strident calls.