mobelha-de-garganta-preta vs mobelha-de-bico-amarelo

The most reliable field mark to distinguish the Black-throated Diver from the White-billed Diver is the bill color: the Black-throated Diver has a dark bill, while the White-billed Diver features a distinctive pale or yellowish bill. Both species are similar in structure, but the bill color is a key differentiator.

Focus on the bill color: Black-throated Diver has a dark bill, whereas White-billed Diver has a pale or yellowish bill. This difference is consistent across seasons and ages, making it a reliable field mark.