Saunders's Gull vs Bonaparte's Gull

In short

Saunders's Gull and Bonaparte's Gull can be distinguished by their size and plumage. Saunders's Gull is smaller with a more delicate build, while Bonaparte's Gull has a distinctive black hood in breeding plumage. Both species exhibit graceful flight patterns, but their habitats and behaviors differ significantly.

Identification tips

• Size: Saunders's Gull is smaller and more delicate.
• Breeding Plumage: Look for the black hood in Bonaparte's Gull.
• Non-breeding Plumage: Bonaparte's Gull has a dark ear spot; Saunders's Gull has a black cap.
• Habitat: Bonaparte's Gull is more likely to be found in inland and arboreal settings during breeding.
• Flight: Both species have graceful, buoyant flight, but Bonaparte's Gull is more tern-like.

Size

Saunders's Gull is smaller and more delicate compared to Bonaparte's Gull.

Plumage

In breeding plumage, Bonaparte's Gull has a distinctive black hood, whereas Saunders's Gull has a white head with a black cap. Non-breeding Bonaparte's Gulls have a white head with a dark ear spot, which can be confused with Saunders's Gull.

Behaviour

Bonaparte's Gull often nests in trees and is known for its tern-like flight. Saunders's Gull is less arboreal and tends to be found in coastal areas.

Habitat

Saunders's Gull is typically found in coastal regions, while Bonaparte's Gull breeds in remote taiga and boreal forest habitats, often near water bodies.

Voice

Vocalizations are not a primary distinguishing feature between these two species in the field.