Black-throated Diver vs Pacific Diver

In short

The Black-throated Diver (Gavia arctica) and Pacific Diver (Gavia pacifica) are closely related loons, often confused due to their similar appearance. Key differences include the Black-throated Diver's more robust bill and distinct breeding plumage patterns. Observing habitat and migration patterns can also aid in identification.

Identification tips

• Bill shape: Black-throated Diver has a more robust bill.
• Breeding plumage: Look for the black throat and checkerboard back in Black-throated Diver.
• Habitat: Black-throated Diver is more likely on freshwater during migration; Pacific Diver is more marine.
• Location: Consider geographic range, especially during breeding and migration seasons.

Size

Both species are similar in size, but the Black-throated Diver tends to be slightly larger and more robust.

Plumage

In breeding plumage, the Black-throated Diver has a distinctive black throat and a checkerboard pattern on the back, while the Pacific Diver has a more uniform grayish head and neck with a less pronounced pattern. In non-breeding plumage, both species appear similar with grayish tones, but the Pacific Diver may have a slightly paler face.

Behaviour

Both species exhibit similar diving behavior for feeding, but the Black-throated Diver may be seen more frequently on freshwater bodies during migration.

Habitat

The Black-throated Diver is often found on freshwater lakes during breeding and migration, while the Pacific Diver is more strictly marine outside the breeding season, frequenting coastal waters.

Voice

Vocalizations are generally similar, with both species producing wailing and yodeling calls, but detailed differences are subtle and may require experience to discern.