Black-throated Diver vs Great Northern Diver

In short

The Black-throated Diver (Gavia arctica) and Great Northern Diver (Gavia immer) are similar loons, but can be distinguished by size and plumage. The Great Northern Diver is larger with a thicker neck and bill, while the Black-throated Diver has a more slender appearance. Both species have distinctive vocalizations, but these are more useful when heard than seen.

Identification tips

1. Size and Shape: Look for the larger size and thicker neck of the Great Northern Diver. 2. Breeding Plumage: Note the black throat with a white stripe on the Black-throated Diver. 3. Vocalizations: Listen for the more complex calls of the Great Northern Diver. 4. Habitat: Consider the location; the Great Northern Diver is more common in North America during winter.

Size

The Great Northern Diver is larger and bulkier than the Black-throated Diver, with a thicker neck and more robust bill.

Plumage

In breeding plumage, the Black-throated Diver has a distinctive black throat with a white vertical stripe, while the Great Northern Diver has a black head and neck with a greenish sheen and white spots on the back. In non-breeding plumage, both species are more similar, but the Great Northern Diver retains a bulkier profile.

Behaviour

Both species are diving birds, primarily piscivorous, and exhibit similar behaviors such as territoriality and social gatherings.

Habitat

The Black-throated Diver breeds on freshwater lakes in northern Europe and Asia, while the Great Northern Diver breeds across Canada, Alaska, and parts of Europe. Both species winter along coasts, but the Great Northern Diver is more widespread in North America.

Voice

The Great Northern Diver is known for its haunting yodels and wails, which are more complex than the calls of the Black-throated Diver. However, vocalizations are best used for identification when heard.