Black-throated Diver vs White-billed Diver

The Black-throated Diver (Gavia arctica) and White-billed Diver (Gavia adamsii) are both large loons with similar body shapes, but they can be distinguished by their bills: the White-billed Diver has a pale, ivory-colored bill, while the Black-throated Diver's bill is dark. Both species have similar plumage patterns, but the White-billed Diver is generally larger and bulkier.

1. Bill Color: Look for the pale, ivory-colored bill of the White-billed Diver compared to the dark bill of the Black-throated Diver. 2. Size and Bulk: The White-billed Diver is larger and bulkier. 3. Breeding Plumage: The Black-throated Diver has a black throat patch in breeding season. 4. Habitat: Consider the breeding habitat; White-billed Divers are more likely in Arctic tundra regions.

The White-billed Diver is generally larger and bulkier than the Black-throated Diver.

Both species have similar plumage with dark upperparts and lighter underparts. However, the Black-throated Diver has a distinctive black throat patch during the breeding season, while the White-billed Diver lacks this feature.

Both species are territorial during breeding, defending their chosen water bodies. They share incubation duties and care for their young. The White-billed Diver is known to arrive early in breeding areas, sometimes before ice has fully retreated.

The Black-throated Diver breeds in freshwater lakes and rivers in northern Europe and Asia, while the White-billed Diver breeds in low-lying tundra regions of the Arctic, often north of the tree line.

Vocalizations are not well-documented in the provided notes, but both species have typical loon calls, which can be haunting and carry over long distances.