{"id":6907,"date":"2024-11-01T17:43:17","date_gmt":"2024-11-01T17:43:17","guid":{"rendered":"https:\/\/wordpress.viu.ca\/biol325\/?p=6907"},"modified":"2024-11-30T05:13:40","modified_gmt":"2024-11-30T05:13:40","slug":"caspian-tern-the-pirate-of-the-caribbean","status":"publish","type":"post","link":"https:\/\/wordpress.viu.ca\/biol325\/2024\/11\/01\/caspian-tern-the-pirate-of-the-caribbean\/","title":{"rendered":"Caspian Tern: The Pirate of the Caribbean"},"content":{"rendered":"\n

Imagine you are a small tern species flying over the Caribbean Sea bringing a fish back to your chick who is resting in a mixed colony of sea birds. You land on a sandy island and make your way to your hungry begging chick, when a shadow blocks the sunlight. You turn and suddenly the fish has been ripped from your beak. You try to take the fish back, but it is too late, your opponent is larger than you and you don’t stand a chance against him. The pirate thief is your neighbour, the Caspian Tern.<\/p>\n\n\n\n

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Adult Caspian Tern in breeding plumage carrying a fish in its bill.<\/em> Credit: Jay McGowen<\/figcaption><\/figure>\n\n\n\n

Taxonomy<\/h2>\n\n\n\n

Hydroprogne caspia<\/em><\/strong> <\/p>\n\n\n\n

Class Aves<\/p>\n\n\n\n

Order Charadriiformes<\/p>\n\n\n\n

Family Laridae<\/p>\n\n\n\n

Identification<\/h2>\n\n\n\n

Caspian Terns can best be identified by their thick bright-red bill, often with a dark marking at the tip of the bill, and their dark wingtips (Stockwell et al., 2022). Adults have a white body with light grey wings. During breeding they have a solid black cap and during non-breeding the cap is more subdued with light black streaking(eBird). Juveniles have less sharp colours and have V-shaped marking on their wings.<\/p>\n\n\n\n

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Breeding adult Caspian Tern.<\/em> Credit: Dick Daniels<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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Non-breeding adult Caspian Tern.<\/em> Credit: Terence Alexander<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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Juvenile Caspian Tern<\/em>. Credit: Mason Maron<\/figcaption><\/figure>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

The Caspian Tern can be distinguished from the similar Royal Tern who is slightly smaller, has a forked tail and has a thinner bill that is more orange with no dark marking at the end (eBird).<\/p>\n\n\n\n

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Adult Royal Tern<\/em>. Credit: Denny Swaby<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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Adult Caspian Tern<\/em>. Credit: Esme Rosen<\/figcaption><\/figure>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n\n\n

Caspian Terns are the largest terns in the world and are about the size of an American Crow (All About Birds). They have sexually monochromatic plumage, meaning the males and females look the same, but the males have been shown to have longer head and bill length (Ackerman et al., 2008).<\/p>\n\n\n\n

The Caspian Tern’s call is a loud raspy \u201cscream\u201d that sounds like a gull with a frog in its throat (eBird). It is mildly unpleasant, so you have been warned.<\/p>\n\n\n\n

Caspian Tern adult call<\/em>. Credit: Audubon<\/figcaption><\/figure>\n\n\n\n
Juvenile Caspian Tern call<\/em>. Credit: Audubon <\/figcaption><\/figure>\n\n\n\n

Food and Feeding Behaviour<\/h2>\n\n\n\n

Caspian Terns mainly feed on fish such as chum, coho, chinook, and sockeye salmon, steelhead, Pacific sardine, rock bass, and many more(All About Birds). Crustaceans such as crayfish, large insects, and the young of other bird species are on the menu occasionally as well.<\/p>\n\n\n\n

To find their food Caspian Terns will fly between 10 and 100 feet above the water with their bill pointed downward, scanning the water (All About Birds). When they see a tasty meal, they dive at the unsuspecting prey, grabbing it with their large bill under the water. After quickly leaving the water, they will either swallow the fish instantly or carry it to their mate or chick.<\/p>\n\n\n\n

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Adult Caspian Tern with its bill pointed down scanning the water for food as it glides over the ocean.<\/em> Credit: Sasha Cahill<\/figcaption><\/figure>\n\n\n\n

Sometimes the pirate Caspian Tern will display kleptoparasitism which is when an individual steals food from another bird (All About Birds). <\/p>\n\n\n\n

Caspian Terns require abundant populations of fish and clear waters so they are good indicators of the health of an ecosystem (Birdbot, n.d.). They play an important role in their ecosystem as a top predator, and help maintain healthy aquatic life.<\/p>\n\n\n\n

Habitat and Distribution<\/h2>\n\n\n\n

Caspian Terns can be seen on every continent apart from Antarctica (Boyd, 2015). They like to remain near water including marine, brackish, and freshwater environments, and they are happy in both urban areas or more undisturbed environments (Stockwell et al., 2022). In North America their breeding distribution is widespread, breeding in colonies inland surrounding lakes or rivers and along both the west and east coasts (Boyd, 2015). They also breed in areas of Europe and largely in Kazakhstan, many breeding around their namesake, the Caspian Sea. They have a wide overwinter range as well, with many populations in Africa and around the Gulf of Mexico and the Caribbean Sea (All About Birds). Populations in Australia tend to stick to what they know and do not migrate, but rather undergo shorter movements from tight breeding colonies to less crammed foraging sites (Stockwell, 2022).<\/p>\n\n\n\n

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Map of the Caspian Tern’s global range (All About Birds).<\/em><\/figcaption><\/figure>\n\n\n\n

Nesting Behaviour<\/h2>\n\n\n\n

A male Caspian Tern will perform courtship displays by flying back and forth with a fish in his bill. He will land next to the female and present the fish while nodding (All About Birds). If the female likes his dance, she will accept the fish and perform a little dance of her own hunching down and then jerking her bill upwards. When the Caspian Terns have paired up they perform courtship flights over the colony breeding grounds.<\/p>\n\n\n\n

Caspian Terns prefer to nest in breeding colonies in open areas close to water with little vegetation and are frequently nesting alongside other gull and tern species (Boyd, 2015). They nest in what is called a scrape nest. This is a depression in the ground that may or may not have lining material added to it (Reid et al., 2002).<\/p>\n\n\n\n

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Caspian Tern chick beside two eggs in a nest scrape. <\/em>Credit: George Walter<\/figcaption><\/figure>\n\n\n\n

The male and female pair will select a site together and make a scrape in an open area with little vegetation (All About Birds). The couple might line the scrape with dried vegetation and surround it with pebbles, shell fragments, sticks, or other objects found close by.<\/p>\n\n\n\n

The female will generally lay 1-3 eggs once a year and incubate the eggs for 25-28 days with the males help (All About Birds). Once hatched the young will only stay in the nest for 1-2 days, as they come out of the eggs wide-eyed with a full down coat ready to take on the world. Both parents will play a role in egg incubation, feeding the chick, and defending the nest (Stockwell et al., 2022).<\/p>\n\n\n\n

Interesting Facts<\/h2>\n\n\n\n