Bonaparte's gull (''Chroicocephalus philadelphia'') is a member of the gull family Laridae found mainly in northern
North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
. At in length, it is one of the smallest species of gull. Its plumage is mainly white with grey upperparts. During breeding season, Bonaparte's gull gains a slaty-black hood. The sexes are similar in appearance.
Taxonomy and etymology
When
George Ord
George Ord, Jr. (March 4, 1781 – January 24, 1866) was an American Zoology, zoologist who specialized in North American ornithology and mammalogy. Based in part on specimens collected by Lewis and Clark Expedition, Lewis and Clark in the North ...
first described Bonaparte's gull in 1815, he gave it the scientific name ''Sterna philadelphia'', and the English name 'Banded-tail Tern';
the description clearly identifies it as a bird in first-winter plumage, while "The slender and tern-like form of the bill probably induced Mr. Ord to put it in ''Sterna''".
Most later taxonomists assigned it to the genus ''
Larus
''Larus'' is a large genus of gulls with worldwide distribution (by far the greatest species diversity is in the Northern Hemisphere).
Many of its species are abundant and well-known birds in their ranges. Until about 2005–2007, most gulls ...
'', a longtime catch-all for most of the gull species. However, in 1858,
George Newbold Lawrence
George Newbold Lawrence (October 20, 1806 – January 17, 1895) was an American businessman and amateur ornithologist.
Early life
Lawrence was born in the city of New York on October 20, 1806.
From his youth, Lawrence was a lover of birds and sp ...
moved the species to the genus ''
Chroicocephalus
''Chroicocephalus'' is a genus of medium to relatively small gulls which were included in the genus ''Larus'' until genetic evidence published in 2005 showed that ''Larus'' as then constituted was paraphyly, paraphyletic. Ten species are currentl ...
'',
and some taxonomists followed suit.
Subsequent molecular DNA studies have shown that this species fits neatly into a clade with other ''Chroicocephalus'' "hooded" gulls, and that it is in a close-to-
basal position in that grouping.
Based on these studies, the
American Ornithologists' Union
The American Ornithological Society (AOS) is an ornithological organization based in the United States. The society was formed in October 2016 by the merger of the American Ornithologists' Union (AOU) and the Cooper Ornithological Society. Its ...
, which had previously assigned the species to the genus ''Larus'', restored it to ''Chroicocephalus'' in 2008.
It is
monotypic
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...
across its range.
The species is named after
Charles Lucien Bonaparte
Charles Lucien Jules Laurent Bonaparte, 2nd Prince of Canino and Musignano (24 May 1803 – 29 July 1857) was a French naturalist and ornithology, ornithologist, and a nephew of Napoleon. Lucien and his wife had twelve children, including Cardinal ...
, a French
ornithologist
Ornithology, from Ancient Greek ὄρνις (''órnis''), meaning "bird", and -logy from λόγος (''lógos''), meaning "study", is a branch of zoology dedicated to the study of birds. Several aspects of ornithology differ from related discip ...
(and nephew to the former French emperor
Napoleon Bonaparte
Napoleon Bonaparte (born Napoleone di Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French general and statesman who rose to prominence during the French Revolution and led Military career ...
) who spent eight years in America, contributing to the understanding of the taxonomy and nomenclature of birds there and elsewhere. Its genus name, ''Chroicocephalus'', is a combination of the
Greek
Greek may refer to:
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group
*Greek language, a branch of the Indo-European language family
**Proto-Greek language, the assumed last common ancestor of all kno ...
words , an adjective form of meaning "colour", and meaning "head". This refers to the dark heads that most gulls in this genus show during the breeding season. The
specific epithet
In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...
''philadelphia'' is a
Latinized adjective meaning "from
Philadelphia
Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...
", a reference to the location from which the
type specimen
In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...
was collected.
Description
Bonaparte's gull is among the smallest of the
gull
Gulls, or colloquially seagulls, are seabirds of the subfamily Larinae. They are most closely related to terns and skimmers, distantly related to auks, and even more distantly related to waders. Until the 21st century, most gulls were placed ...
species; only
little gull
The little gull (''Hydrocoloeus minutus''), is a species of gull belonging to the family Laridae which is mainly found in the Palearctic with some small colonies in North America. It breeds on freshwater lakes and marshes, and spends winters at ...
and
Saunders's gull are smaller.
Adults range from in length, with a wingspan of and a weight of .
There is no difference in plumage or bare part colour between the sexes,
though males tend to be heavier than females.
Bonaparte's gull is smaller-bodied, smaller-headed, and smaller-billed than the other common hooded gulls of North America.
The adult has grey upperparts and white underparts, with, unlike other ''Chroicocephalus'' gulls, the grey extending up the rear of the neck to just below the head; its wingtips are black and white striped above with the outer four primary feathers white with a black tip, and the other primary feathers grey with a black tip; the whole wing is very pale below. In breeding plumage, it has a slaty black hood, which it loses in non-breeding plumage. Its short, thin bill is black, and its legs are pinkish-red in winter, orangish-red in summer.
The juvenile plumage, usually only seen on the breeding grounds, is scalloped brown on the back, and patchy brown on the head; they
moult
In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at ...
into first-winter plumage in August mostly before migrating south.
First year birds are more like the adults with a grey back, but retain a brown bar across the forewing, blackish tips to the secondary feathers, and a black tip to the tail; they have the same plumage in winter and the following summer, but the summer plumage is paler due to wear and fading. Fewer than 5 percent of Bonaparte's gulls acquire a dark hood in their first summer, and on those that do, the hood is duller than on breeding adults.
Two-year old birds mostly gain full adult plumage, but a few retain signs of immaturity such as brown spots on the forewing and dark tips to some of the tail feathers.
The most similar potential confusion species is the Old World
black-headed gull
The black-headed gull (''Chroicocephalus ridibundus'') is a small gull that breeds in much of the Palearctic in Europe and Asia, and also locally in smaller numbers in coastal eastern Canada. Most of the population is migratory and winters fu ...
, which each being a regular, though scarce or rare, winter visitor within the wintering range of the other. They can best be distinguished by the smaller size of Bonaparte's gull, its slenderer, darker bill, pale grey rear of the neck, pinker legs, and in flight, by the conspicuously whiter underwing, lacking the dark uderside of the primary feathers of black-headed gull.
Little gull
The little gull (''Hydrocoloeus minutus''), is a species of gull belonging to the family Laridae which is mainly found in the Palearctic with some small colonies in North America. It breeds on freshwater lakes and marshes, and spends winters at ...
can also be confused in immature plumages; it is even smaller than Bonaparte's gull, and the dark bar on the forewing of year-old birds is black, not dark brown. Adult little gulls, with their uniform pale grey upperwing and blackish underwing, are far less likely to be confused.
Distribution and habitat
Bonaparte's gull breeds in
boreal forest
Taiga or tayga ( ; , ), also known as boreal forest or snow forest, is a biome characterized by pinophyta, coniferous forests consisting mostly of pines, spruces, and larches. The taiga, or boreal forest, is the world's largest land biome. I ...
across southern
Alaska
Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
and much of interior western
Canada
Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
, as far east as central
Quebec
Quebec is Canada's List of Canadian provinces and territories by area, largest province by area. Located in Central Canada, the province shares borders with the provinces of Ontario to the west, Newfoundland and Labrador to the northeast, ...
and south to within of the Canada – United States border.
It avoids dense stands of conifers, instead choosing more open areas, such as the treed edges of
bog
A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and musk ...
s,
fen
A fen is a type of peat-accumulating wetland fed by mineral-rich ground or surface water. It is one of the main types of wetland along with marshes, swamps, and bogs. Bogs and fens, both peat-forming ecosystems, are also known as mires ...
s, marshes, ponds, or islands. It typically nests within of open water.
It winters along the coasts of North America, and in the Great Lakes.
Vagrancy
It is a rare but annual visitor to western Europe and the
Azores
The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...
, where it generally associates with
black-headed gull
The black-headed gull (''Chroicocephalus ridibundus'') is a small gull that breeds in much of the Palearctic in Europe and Asia, and also locally in smaller numbers in coastal eastern Canada. Most of the population is migratory and winters fu ...
s.
In
Great Britain
Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...
, the number of records increased from averages of six per year at the start of the 21st century to around 12 per year by 2018–2022; the reason for this increase is unknown.
Individuals often return to particular sites over a number of years; one at
Bamburgh
Bamburgh ( ) is a village and civil parish on the coast of Northumberland, England. It had a population of 454 in 2001, decreasing to 414 at the 2011 census.
Bamburgh was the centre of an independent north Northumbrian territory between 867 a ...
in Northumberland returned for its 12th autumn in 2024.
In 2017 a breeding pair was found in northwestern
Iceland
Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...
.
Bonaparte's gull is an occasional non-breeding vagrant to the
Hawaiian Islands
The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...
,
and vagrants have also been recorded west to
Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
and south to
Brazil
Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
and
Senegal
Senegal, officially the Republic of Senegal, is the westernmost country in West Africa, situated on the Atlantic Ocean coastline. It borders Mauritania to Mauritania–Senegal border, the north, Mali to Mali–Senegal border, the east, Guinea t ...
.
Behaviour
They are
migratory and most move southeast or southwest to coastal waters, also the
Great Lakes
The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...
. They are graceful in flight, more like
terns
Terns are seabirds in the family (biology), family Laridae, subfamily Sterninae, that have a worldwide distribution and are normally found near the sea, rivers, or wetlands. Terns are treated in eleven genus, genera in a subgroup of the fam ...
than most other gulls.
Feeding
Like most gulls, Bonaparte's gull has a varied diet, with prey items changing over the course of the year, and from year to year. During the breeding season, it is largely
insectivorous
A robber fly eating a hoverfly
An insectivore is a carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects.
The first vertebrate insectivores we ...
.
It is known to quickly congregate in large numbers to take advantage of
termite
Termites are a group of detritivore, detritophagous Eusociality, eusocial cockroaches which consume a variety of Detritus, decaying plant material, generally in the form of wood, Plant litter, leaf litter, and Humus, soil humus. They are dist ...
dispersal flights, circling over the emerging swarm and hovering briefly to take the insects in flight.
It also gathers in large numbers to feed on the eggs of
spawning
Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...
salmon
Salmon (; : salmon) are any of several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the genera ''Salmo'' and ''Oncorhynchus'' of the family (biology), family Salmonidae, native ...
, alighting on the water and, if necessary, diving to take drifting eggs.
During migration and into the winter, insects are first supplemented, then replaced by other food items, including fish, small crustaceans, mollusks,
euphausiids, marine worms, and other invertebrates.
At least one immature bird has been recorded as having fed on walnut meat.
Bonaparte's gulls are known to engage in
kleptoparasitism
Kleptoparasitism (originally spelt clepto-parasitism, meaning "parasitism by theft") is a form of feeding in which one animal deliberately takes food from another. The strategy is evolutionarily stable when stealing is less costly than direct f ...
, and have been observed stealing earthworms from foraging
dunlins and
black-bellied plovers.
Breeding

Bonaparte's gulls begin breeding at two years of age; they are thought to be
monogamous
Monogamy ( ) is a relationship of two individuals in which they form a mutual and exclusive intimate partnership. Having only one partner at any one time, whether for life or serial monogamy, contrasts with various forms of non-monogamy (e.g. ...
.
The breeding season begins in mid-June.
Courting pairs perform swooping display flights, calling loudly and diving at each other, and then drop down to perch on a branch. Crouched and facing each other, with neck and crown feathers erected and wings slightly raised, they scream at each other with bills opened wide, bobbing up and down as they do so. This display can continue for several minutes before ending abruptly; afterwards, the birds may sit quietly together for some time before separating again.
They raise a single
brood per year,
nesting singly or in loose
colonies
A colony is a territory subject to a form of foreign rule, which rules the territory and its indigenous peoples separated from the foreign rulers, the colonizer, and their '' metropole'' (or "mother country"). This separated rule was often or ...
of , with
nests spaced at least apart. Unlike most other gulls, Bonaparte's gulls typically nest in trees — almost exclusively conifers, most often
black spruce
''Picea mariana'', the black spruce, is a North American species of spruce tree in the pine family. It is widespread across Canada, found in all 10 provinces and all 3 territories. It is the official tree of Newfoundland and Labrador and is tha ...
, but also
northern whitecedar,
tamarack
''Larix laricina'', commonly known as the tamarack, hackmatack, eastern larch, black larch, red larch, or American larch, is a species of larch native to Canada, from eastern Yukon and Inuvik, Northwest Territories east to Newfoundland, and als ...
and
jack pine
Jack pine (''Pinus banksiana''), also known as grey pine or scrub pine, is a North American pine.
Distribution and habitat
Its native range in Canada is east of the Rocky Mountains from the Mackenzie River in the Northwest Territories t ...
.
Both sexes help to build the nest,
which is a platform of small sticks, sometimes with
lichen
A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
, moss or marsh vegetation added, measuring about in diameter.
Most nests are placed above the ground, and within of open water, though they have been found low as , as high as , and as far as from open water. They are only rarely placed on the ground, except in the far north where trees are absent. Adults are aggressive in defending their nests, chasing away even large potential
predator
Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
s such as
hawk
Hawks are birds of prey of the family Accipitridae. They are very widely distributed and are found on all continents, except Antarctica.
The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks, and others. This ...
s,
common raven
The common raven or northern raven (''Corvus corax'') is a large all-black passerine bird. It is the most widely distributed of all Corvidae, corvids, found across the Northern Hemisphere. There are 11 accepted subspecies with little variatio ...
s and humans. There is some evidence that human activity in the area of their nests may cause decreased productivity — they are known to travel as far as a kilometre (about a half mile) to
mob people, — but, contrarily, some choose to nest near human habitation.
The female lays a
clutch
A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...
of , with most nests containing . The eggs are
subelliptical, slightly glossy and smooth, measuring
and weighing .
They range in colour from pale to medium green, olive or buff, and may be variably marked with spots, blotches, or scrawls of brown, grey, violet, or black; these markings may be fine and evenly distributed over the entire surface of the egg, or thick and concentrated towards the egg's larger end.
The eggs are
incubated by both parents for .
Studies have shown that breeding populations can be significantly impacted by bad weather. In one multi-year study in
Churchill, Manitoba
Churchill is a subarctic port town in northern Manitoba, Canada, on the west shore of Hudson Bay, roughly from the Manitoba–Nunavut border. It is most famous for the many polar bears that move toward the shore from inland in the autumn, leadi ...
, more than half of the eggs laid in observed nests were blown out of those nests during storms; only 42% of eggs survived to hatching.
Hatchling Bonaparte's gulls are
semi-precocial, emerging from their eggs covered with
natal down feathers, and with eyes already opened. The down is yellowish-buff, greyer on the flanks and belly, and somewhat pinkish on the breast, with dark brown mottling on the upperparts and head. The bill is blue-black with a pinkish base, and the legs and feet are pinkish-buff.
Young birds typically leave the nest within of hatching, jumping out and following their parents to the nearest open water.
Both parents tend the young.
The time it takes the young to
fledge
Fledging is the stage in a flying animal's life between egg, hatching or birth and becoming capable of flight.
This term is most frequently applied to birds, but is also used for bats. For altricial birds, those that spend more time in vulnera ...
is unknown.
Bonaparte's gulls may live to 18 years.
Voice
Bonaparte's gull has a voice described as nasal and raspy, with calls variously transcribed as or .
Conservation
Because of its extremely large range and its increasing population, Bonaparte's gull is listed as a species of
least concern
A least-concern species is a species that has been evaluated and categorized by the International Union for Conservation of Nature (IUCN) as not being a focus of wildlife conservation because the specific species is still plentiful in the wil ...
by the
International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...
.
In North America, it is protected by the
Migratory Bird Treaty Act
The Migratory Bird Treaty Act of 1918 (MBTA), codified at (although §709 is omitted), is a United States federal law, first enacted in 1918 to implement the convention for the protection of migratory birds between the United States and Canada. ...
.
Because it occurs in Europe and Africa only as a vagrant, it is not protected by the
Agreement on the Conservation of African-Eurasian Migratory Waterbirds.
The species is known to be preyed upon by
peregrine falcon
The peregrine falcon (''Falco peregrinus''), also known simply as the peregrine, is a Cosmopolitan distribution, cosmopolitan bird of prey (raptor) in the family (biology), family Falconidae renowned for its speed. A large, Corvus (genus), cro ...
s.
Like many birds, it hosts a number of internal and external parasites. The
linguatulid species ''
Reighardia sternae'',
a tiny, worm-like crustacean, is sometimes found in the gull's air sacs.
The
acanthocephala
Acanthocephala ( Greek , ' 'thorn' + , ' 'head') is a group of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses t ...
worm ''Corynosoma bipapillum'' is sometimes found in the bird's posterior gut,
as is the intestinal worm ''Echinostomum spinulosum''.
''Gigantobilharzia lawayi'', a
schistosome
''Schistosoma'' is a genus of trematodes, commonly known as blood flukes. They are parasitic flatworms responsible for a highly significant group of infections in humans termed ''schistosomiasis'', which is considered by the World Health Organ ...
(or blood fluke) may be carried in the
capillaries
A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the in ...
.
Externally, it is known to carry several species of
lice
Louse (: lice) is the common name for any member of the infraorder Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera was previously recognized as an order, until a 2021 genetic study determined th ...
, including ''
Actornithophilus
''Actornithophilus'' is a genus of louse in the family Amblycera. It was circumscription (taxonomy), circumscribed by Gordon Floyd Ferris in 1916. Its species are ectoparasites of birds in the order Charadriiformes.
Species
, the following spec ...
funebre'', ''Degeeriella atrimarginata'', ''Degeeriella punctata'', ''
Menopon'' species, and ''Philopterus gonothorax''.
Chroicocephalus philadelphia nesting Alaska.jpg, Ground nesting in Katmai National Park, Alaska
Bonaparte's Gull (20714333809).jpg, Showing the white underwing
Bonaparte's Gull in breeding plumage - 52018530795.jpg, In flight, showing the upperwing pattern
2021-11-14 Bonaparte's Gull, Stag Rocks, Northumberland, UK 2.jpg, Vagrant in UK
References
External links
*
*
*
*
*
Bonaparte's gull - ''Larus philadelphia''- USGS Patuxent Bird Identification InfoCenter
*
*
*
{{Taxonbar, from=Q629525
Bonaparte's gull
Native birds of Alaska
Birds of Canada
Bonaparte's gull
Taxa named by George Ord
Taxobox binomials not recognized by IUCN