Gull-billed Tern vs Black Tern

In short

The Gull-billed Tern and Black Tern are both medium-sized terns but differ significantly in structure and plumage. The Gull-billed Tern has a stocky build with a short, heavy black bill, while the Black Tern is more delicate with a slender bill and a distinctive black head and body in breeding plumage.

Identification tips

1. Bill Shape: Gull-billed Tern has a short, heavy, straight black bill, while Black Tern has a slender bill. 2. Plumage: Look for the black cap and white body in Gull-billed Tern during breeding; Black Tern has a black head and body in breeding plumage. 3. Flight Pattern: Black Tern's flight is more buoyant and erratic compared to the more direct flight of the Gull-billed Tern. 4. Habitat: Consider the habitat; Black Tern is more likely in freshwater marshes, while Gull-billed Tern can be found in a wider range of wetland habitats.

Size

Gull-billed Tern is generally larger (33–38 cm long) compared to the Black Tern, which is smaller and more slender.

Plumage

Gull-billed Tern has a pale gray back and wings with a white body and a black cap in breeding adults. Black Tern, in breeding plumage, is strikingly different with a black head and body, contrasting with gray wings and back. In non-breeding plumage, Black Tern becomes much paler but retains a dark patch behind the eye.

Behaviour

Black Tern is highly social, often seen in flocks and has a buoyant, zigzag flight reminiscent of a swallow. Gull-billed Tern is less social and has a more direct flight.

Habitat

Gull-billed Tern is often found in coastal and inland wetlands, while Black Tern prefers freshwater marshes and wetlands, especially during breeding season.