Bonaparte's Gull

The Bonaparte's Gull (Chroicocephalus philadelphia) is a dainty member of the gull family Laridae, easily distinguished by its petite stature. Adults measure between 28 to 38 cm in length, with a wingspan of 76–84 cm and a body mass of 180–225 g. The plumage is predominantly white with grey upperparts. During the breeding season, a striking slaty-black hood adorns the bird, which is lost in non-breeding plumage. Both sexes are similar in appearance, with males typically being slightly heavier.

Identification Tips

This species is one of the smaller gulls, with a smaller body, head, and bill compared to other hooded gulls in North America. The adult Bonaparte's Gull has a short, thin black bill and orangish-red legs. Its wingtips are black above and pale below, and the breeding plumage features a distinctive slaty black hood.

Habitat

Bonaparte's Gull breeds in the boreal forests, preferring open areas near the treed edges of bogs, fens, marshes, ponds, or islands. It nests within 60 m of open water and typically avoids dense conifer stands.

Distribution

This gull is found mainly in northern North America, breeding across southern Alaska and interior western Canada to central Quebec and south near the United States/Canada border. It winters along the coasts of North America and in the Great Lakes. It is a rare vagrant to western Europe and the Azores.

Behaviour

Bonaparte's Gulls are migratory, moving to coastal waters or the Great Lakes. They exhibit graceful flight, reminiscent of terns. They are known to be monogamous and begin breeding at two years of age, raising a single brood per year.

Song & Calls

The voice of the Bonaparte's Gull is described as nasal and raspy, with calls that can be transcribed as "cherr" or "cheeer."

Breeding

The breeding season begins in mid-June, with courtship involving swooping display flights and loud calling. Nests are built in trees, usually conifers, and are platforms of small sticks. The female lays 2–4 eggs, which are incubated by both parents for 22–24 days. Chicks are semi-precocial and leave the nest within 2–7 days of hatching.

Diet and Feeding

Bonaparte's Gull has a varied diet that changes seasonally. It is largely insectivorous during the breeding season, feeding on emerging termites and eggs of spawning salmon. In migration and winter, the diet shifts to include fish, crustaceans, mollusks, and other invertebrates. They also engage in kleptoparasitism, stealing food from other birds.

Conservation status

The Bonaparte's Gull is listed as Least Concern by the IUCN due to its large range and increasing population. It is protected under the Migratory Bird Treaty Act in North America.