Gaviota Maorí vs Charrán Blanco

The most reliable field mark to distinguish the Black-billed Gull from the White Tern is the bill color: the Black-billed Gull has a distinctive black bill, while the White Tern has a black-tipped bill. Additionally, the Black-billed Gull is a gull species with a more robust body, whereas the White Tern is a more slender seabird.

1. Bill color: Black-billed Gull has a black bill; White Tern has a black-tipped bill. 2. Body structure: Black-billed Gull is more robust; White Tern is slender. 3. Plumage: Black-billed Gull has grey and white plumage; White Tern is entirely white.

The Black-billed Gull typically has a grey and white plumage with a black bill, while the White Tern is entirely white with a black-tipped bill.