{"id":5010,"date":"2022-10-28T16:21:33","date_gmt":"2022-10-28T16:21:33","guid":{"rendered":"https:\/\/wordpress.viu.ca\/biol325\/?p=5010"},"modified":"2022-11-04T22:22:11","modified_gmt":"2022-11-04T22:22:11","slug":"bonapartes-gull","status":"publish","type":"post","link":"https:\/\/wordpress.viu.ca\/biol325\/2022\/10\/28\/bonapartes-gull\/","title":{"rendered":"Bonaparte’s Gull: Unmasked"},"content":{"rendered":"\n

Now I know what you\u2019re thinking: \u201cNo way am I really going to read a long-winded blog post about some boring seagull when there are so many other interesting bird blogs about much cooler that birds I could be reading\u201d. But trust me this once, this is a gull unlike any that you have heard of before; and I hope by the end of reading this you will come to appreciate these handsome\u2014and frankly, criminally underrated\u2014birds almost as much as I do.<\/p>\n\n\n\n

Classification: How did it get the name?<\/h2>\n\n\n\n

The Bonaparte\u2019s gull (Chroicocephalus philadelphia<\/em>) is a member of the Laridae family (gulls and terns) in the order Charadriiformes (sea and shorebirds). Its common name was given to honour, not the well-known revolutionary Napoleon, but his nephew Charles Lucien Bonaparte; who you might be surprised to learn was a renowned ornithologist who worked both in the United States and in Europe. As of 2022, he is credited by the International Ornithological Committee<\/a> for coining the Latin names of more than 600 genera, species and subspecies of birds in his career. But enough about the man, lets talk birds\u2026<\/p>\n\n\n\n

Identification: How can I tell them apart from other gulls?<\/h2>\n\n\n\n

Bonaparte\u2019s gull is rather small and sleek compared to a lot of other gull species, close in size to an American Crow. Their plumage is largely similar to most other gulls, with white bodies and light grey backs and wings. Where they differ from most gulls however, is the colouration of their heads.<\/p>\n\n\n\n

In breeding plumage, the Bonaparte\u2019s gull can be easily identified as they look ready to pull off an elaborate bank heist. With an all-black head with only a little white plumage left around the eyes, this colour pattern gives the appearance of a black balaclava worn to conceal their identities, but ironically giving them away. In their non-breeding plumage, these gulls lack the full black balaclava, but can still be identified by a black spot on their cheek behind the eye.<\/p>\n\n\n\n

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Breeding Adult<\/em> (Photo by Jim Sims<\/a>)<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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Non-breeding Adult<\/em> (Photo by Darren Clark<\/a>)<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n

In both adult plumages, the Bonaparte\u2019s gull can also be identified by white wedges on the front side of the wing tips, which contrast the gray colouration of the rest of the wing. Other identifying features include a narrow, all-black beak\u2014colour matched to its black balaclava in breeding plumage\u2014and bright red-orange legs. <\/p>\n\n\n\n

Juvenile Bonaparte\u2019s gulls display the same black spot visible in the adult non-breeding plumage but differ from adults in their mix of brown and grey colouration of the body and wings, and a black band across the end of the tail. The brown patches and black tail band are retained throughout the majority of the gull\u2019s first year of life. Juveniles can also often be identified by black markings present across the whole length of the posterior edge of the wing, while adults only retain black markings on the distal end of the wing. During their first summer, they may begin to display some black feathers on the head, but the balaclava will not be fully formed.<\/p>\n\n\n\n

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Juvenile<\/em> (Anonymous<\/a>)<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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First Winter<\/em> (Alan Wells<\/a>)<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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First Summer<\/em> (Jay McGowan<\/a>)<\/figcaption><\/figure>\n<\/div>\n<\/div>\n<\/div><\/div>\n<\/div>\n<\/div>\n\n\n\n

Migration and Distribution: Where can I find them?<\/h2>\n\n\n\n
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Bonaparte’s gull distribution map<\/em> (All About Birds<\/a>)<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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Bonaparte’s gulls are migratory birds. While they are commonly found across all of North America, their population moves north and south across the continent with the changing of the seasons. These gulls winter on the southern coasts of North America, typically beginning their flight northward around March-April (Burger, J., & Gochfeld, M., 2020). The migration routes they take are varied, but much of the population will follow river valleys, lakes, and other bodies of water. Breeding territory for the Bonaparte\u2019s gull is also vast and dispersed but located mostly in the north-western areas of the continent. Gulls can usually be found in breeding grounds from May to early September (Burger, J., & Gochfeld, M., 2020). Some transatlantic vagrants have also been reported in western Europe and Norway (All About Birds<\/a>).<\/p>\n<\/div>\n<\/div>\n\n\n\n

Habitat and Behaviour – Summer Breeding Season<\/h2>\n\n\n\n

During the breeding season, Bonaparte\u2019s gulls fly inland to the boreal forests of southern Alaska and north-western Canada. While inland, they prefer to stick around wet marshy areas, or near lakes and streams. Bonaparte\u2019s gulls are unique among seagulls in their tendency to construct nests in trees. The nests are usually built near the trunk and can be as high as 50 feet off the ground (All About Birds<\/a>). The construction of these nests is a joint effort of a breeding pair of gulls; and sometimes used over several breeding seasons. Their elevated nests compliment their feeding habits during the breeding season; which consists largely of flying insects, mostly caught on the wing or off the surface of trees and other plants (Braune, B. M., 1987).<\/p>\n\n\n

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Tree nesting of Bonaparte’s gulls is unique among gull species<\/em> (Photo by Christian Artuso<\/a>) <\/figcaption><\/figure>\n<\/div>\n\n\n

Mate selection among Bonaparte\u2019s gulls largely occurs in midair around the nesting grounds: courting gulls will call loudly while swooping and diving at each other in displays of ultimate gull prowess. The courtship ends with two gulls deciding they are impressed with the other\u2019s swooping and screaming, and landing in a nearby tree, where they continue to scream at each other while bills opened upwards and heads bobbing up and down (Twomey, A. C., 1934). Sometimes they will do this for minutes at a time, before they decide that enough is enough and just sit together in silence, enjoying each others company.<\/p>\n\n\n\n

Long call of the Bonaparte’s gull. It may sound very annoying to us, but I assure you the gulls find it very attractive<\/em> (Recording by Peter Boesman<\/a>)<\/figcaption><\/figure>\n\n\n\n
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Once a happy breeding pair of Bonaparte\u2019s gulls is established, the two will collaboratively construct their nest. Breeding gulls value their privacy and personal space, and therefore tend to avoid building nests on already occupied trees; it is rare to see two nests built less than a hundred feet from each other (Twomey, A. C., 1934). The nests are constructed mostly of spruce and tamarack twigs, held together with lichen, and lined with tree bark. <\/p>\n<\/div>\n\n\n\n

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Nesting Bonaparte’s gull with <\/em>hatchlings (Photo by Michael Quinton<\/a>)<\/figcaption><\/figure>\n<\/div><\/div>\n<\/div>\n\n\n\n
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Adult Bonaparte’s gull with two hatchlings <\/em>(Photo by Jess Findlay<\/a>)<\/figcaption><\/figure>\n<\/div><\/div>\n\n\n\n
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Females typically lay a clutch of 2-4 eggs, which are incubated by both parents for about 3 weeks before hatching. Once hatched, the chicks stay in the nest for their first 6-7 days of life before following their parents out (Sandilands, A., 2011; Jehl Jr., J. R., 1971). From the laying of the eggs to the young leaving the nest, the parents will defend the nesting site aggressively against potential predators. They are known to scare off intruders through aerial dives accompanied by shrill calls (Burger, J., & Gochfeld, M., 2020). Due to the elevated placement of most Bonaparte\u2019s gull nests, aerial predators like ravens and hawks pose the biggest threat. However, they have also been known to mob<\/a> humans that have encroached on breeding territory (Twomey, A. C., 1934).<\/p>\n<\/div>\n<\/div>\n\n\n\n

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Downy gull chick<\/em> (From USFWS<\/a>)<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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Adult and chick swimming together<\/em> (From USFWS<\/a>)<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n

Habitat and Behaviour – Non-breeding Winter Season<\/h2>\n\n\n\n
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Over the colder winter months, Bonaparte\u2019s gulls tend to stay closer to the east and west coasts of the United States, as well as Cuba, the Gulf of Mexico, and some Caribbean islands (Latta, S. C., & Rodr\u00edguez, P. G., 2018). Their non-breeding habitats allow for a much greater diversity of feeding opportunities than their northern breeding habitats permit. Non-breeding Bonaparte\u2019s gulls are known to feed in ponds, lakes, river marshes, bays, and oceans (Burger, J., & Gochfeld, M., 2020). Notably, they are almost never found scavenging human refuse around garbage dumps and landfills like many other gull species; they consider themselves above that.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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While ocean feeding, these gulls are known to gather along tidal rips and upwellings as far as 20 km from shore. Their diet here consists mainly of small fish, crustaceans (especially shrimp and krill), and other marine invertebrates (Burger, J., 1988). One interesting feeding technique Bonaparte\u2019s gulls use while out on open water is known as \u201cconveyer belt feeding\u201d, wherein large flocks of gulls fly upwind very close to the water\u2019s surface so they may quickly dive at prey below. When they reach the end of the food patch they quickly fly upward, allowing the wind to carry them back to the start of the que where they may do it all over again, hence the name (All About Birds<\/a>).<\/p>\n<\/div>\n\n\n\n

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Bonaparte’s gull foraging in intertidal zone <\/em>(Photo by Dave Ingram<\/a>)<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n
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