Bonaparte's Gull vs Franklin's Gull

In short

Bonaparte's Gull and Franklin's Gull can be distinguished by their size and hood coloration. Bonaparte's Gull is smaller with a more delicate appearance, while Franklin's Gull is slightly larger and has a more robust build. In breeding plumage, Bonaparte's Gull has a black head, whereas Franklin's Gull's hood is also black but extends further down the neck.

Identification tips

• Size and Structure: Bonaparte's Gull is smaller and more delicate; Franklin's Gull is slightly larger and more robust.
• Breeding Plumage: Bonaparte's Gull has a black hood; Franklin's Gull's hood extends further down the neck.
• Non-breeding Plumage: Bonaparte's Gull has a white head with a dark ear spot; Franklin's Gull retains some hood markings.
• Habitat: Bonaparte's Gull nests in trees in boreal forests; Franklin's Gull nests in marshes.
• Behavior: Bonaparte's Gull has a tern-like flight; Franklin's Gull is often seen in agricultural fields.

Size

Bonaparte's Gull is smaller and more delicate compared to the slightly larger and more robust Franklin's Gull.

Plumage

In breeding plumage, both species have black hoods, but Franklin's Gull's hood extends further down the neck. Bonaparte's Gull has a clean white underbody, while Franklin's Gull may show a pinkish hue. Non-breeding Bonaparte's Gull has a white head with a dark ear spot, whereas Franklin's Gull retains some hood markings.

Behaviour

Bonaparte's Gull often nests in trees and displays a more tern-like flight, while Franklin's Gull nests in large colonies in marshes and is more likely to be seen following agricultural activities.

Habitat

Bonaparte's Gull breeds in remote taiga and boreal forests, often nesting in trees, and winters along coasts. Franklin's Gull breeds in prairie marshes and migrates to South America, often seen in agricultural fields during migration.

Voice

Both species have distinctive calls, but specific differences are not detailed in the sources.