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The Ivory Bill·Birds·Seabirds
 

Bonaparte’s Gulls, Chroicocephalus philadelphia

Bonaparte's gull standing on a rock off shore.

Bonaparte’s Gulls are small gulls that breed in boreal forest habitats near lakes and rivers in North America, particularly in Canada and Alaska, from late May to early July.

Bonaparte’s Gulls are commonly found in mixed coniferous-deciduous forests near water bodies, such as ponds, marshes, and slow-moving rivers, where insects like midges, mayflies, and dragonflies are abundant during the breeding season.

They forage in open water and along shorelines for small fish, aquatic insects, crustaceans, and mollusks. They may also feed on terrestrial insects and invertebrates, particularly during breeding when such prey is plentiful.

Bonaparte’s Gulls exhibit agile flight and precision diving to capture prey, often snatching insects in mid-air or picking them from the water’s surface. Their small size and maneuverability allow them to exploit a variety of prey types in different habitats.

Courtship involves aerial displays where males perform elaborate flights, including dives and twists, accompanied by calls. On the ground, males present food to females as part of courtship feeding rituals, reinforcing pair bonds.

Nest building is typically done by the female, who constructs a shallow cup nest from twigs, grasses, and moss, often placed in conifer trees or shrubs near water. Nests are usually well-hidden to protect from predators.

Egg laying occurs from late May to early June, with the female usually laying two to four eggs. Both parents share incubation duties, which last about 24 to 26 days. Upon hatching, the chicks are semi-precocial, requiring some parental care but able to leave the nest shortly after hatching. Initial diets for chicks consist of regurgitated small fish and insects provided by the parents.

Chicks learn to forage by following their parents and observing their foraging techniques. They face vulnerabilities such as predation by larger birds, mammals, and exposure to harsh weather conditions. Parental care includes leading chicks to food sources and shielding them from predators and adverse weather.

Chick fledging occurs about 25 to 30 days after hatching, with continued guidance from adults as the chicks develop their foraging skills. Their diet evolves to include a wider variety of aquatic and terrestrial prey as they grow.

Bonaparte’s Gulls undertake migratory journeys, leaving their breeding grounds in late July to early September. They follow specific flyways along the Great Lakes and Atlantic coast, traveling to wintering regions in the coastal areas of the southeastern United States, Mexico, and Central America.

Wintering habitats include coastal bays, estuaries, and inland lakes, where they forage for small fish, crustaceans, and aquatic invertebrates. Their diet during winter is diverse, adapting to the availability of food in different coastal and inland water bodies.

Bonaparte’s Gulls typically leave their wintering grounds in late March to early April, returning north to their breeding areas as the ice thaws and water bodies become accessible, providing abundant insect prey for the breeding season.