We're celebrating gulls on the blog this week! Today we'd like to share a bird term that relates to some species of gulls. Let's find out about kleptoparasitism!
Kleptoparasitism is just what it sounds like - parasitism by theft (klepto-). It basically refers to one animal stealing food from another. Before we go on, it should be made clear that gulls are not the only species that engage in this behavior. They aren't even the only birds that do so.
Why would one animal steal food from another? In some cases, the thief takes prey items that it would not be able to capture on its own. Sometimes the kleptoparasite steals food opportunistically, or to save the time and effort of obtaining prey. Kleptoparasitism can also refer to the theft of non-food items, like when Chinstrap Penguins steal nest material from other penguins to use in their own nest.
Birds in the seabird family Skua are known for their kleptoparasitic behavior. Some species of skua obtain a significant percentage of their food using this method, stealing prey caught by other seabirds.
Frigatebirds are known for this behavior as well, giving them the appropriate nickname "pirate of the sea".
Gulls can be both perpetrators and victims of kleptoparasitism. Heermann's Gulls and Laughing Gulls are known to steal fish from Brown Pelicans, snatching anything that escapes from the pelican's bill as it surfaces from a hunt. Gulls may chase others of their own species in order to steal freshly caught prey or found food items.
Chasing down deep diving fish hunters is a way for non-diving gulls to obtain food not otherwise available.
Gulls have also been known to steal food from humans! Has this ever happened to you?
When we had our first Gull Week in 2015, we answered some Frequently Asked Questions About Gulls. Today we're going to answer a few more fun FAQs about the species in this family of seabirds!
What do gulls eat? Are gulls carnivores? What do gulls drink? Gulls tend to be opportunistic omnivores. They'll take every chance to eat almost anything! Gulls feed on fish and other marine animals. They will eat insects, worms, eggs, and small land animals. Gulls may also feed on carrion and garbage, other birds, and plant matter like seeds and fruit. As far as drinking, gulls are able to drink sea water. A special gland helps them excrete the salt before it reaches the kidneys.
What do gulls do in winter? When do gulls migrate? Most gulls migrate between wintering grounds and breeding territory. After mating season is complete, they move to warmer climates. The specific timing of this depends on their breeding calendar. Migration distances range from the Franklin's Gull's yearly trek from Canada to South America, to species that simply disperse to the coast from more inland breeding grounds.
What are baby gulls like? Most baby gulls have downy feathers when they hatch. In most gull species, chicks are precocial (or semi-precocial), meaning that they are relatively mobile and can leave the nesting site within a short time of hatching. Ring-billed Gulls fully leave their nest by 4 days of age. Baby Herring Gulls remain close to their nest site for the first week of life. Young gulls are typically dependent on their parents or other adult gulls for food until they fully fledge.
Where do gulls go at night? Most species of gull are diurnal, meaning they are awake during the day and at rest during the night. Gulls typically like to roost either on the water, or along beaches, dunes, or offshore islands. Sleeping on the water is only preferred when the water is calm. The exception to this is the Swallow-tailed Gull, the world's only nocturnal gull species. Instead of resting at night, they are on the hunt for food.
How can you tell how old a gull is? This is a great part of the challenge of gull identification. There is no simple answer that covers all gull species. Gulls go through different plumages as they reach adulthood and they also go through two yearly molts.
The number of years it takes a gull to reach its full adult plumage ranges from two years for smaller gulls to three or four years for larger birds. Gulls of different ages will have different plumages.
Gulls also go through molts each spring (to "alternate plumage") and fall (to "basic plumage"). During a molt, which may take place over several weeks, the bird may appear to be in between two plumages.
In addition to the changes in a gull's feather appearance, there are changes that may occur to their legs and bills. These may change color as they age or molt!
When you know the specifics of how a species of gull ages and molts, you may be able to tell if a gull is one, two, or three years old, or an adult aged four or older.
Are gulls protected? Sometimes gulls are considered to be nuisance birds. Their level of protection varies from place to place. In the United States, native gulls are protected under the Migratory Bird Treaty Act. In the United Kingdom, they are protected under the Wildlife and Countryside Act 1981 and the Wildlife Order 1985 (Northern Ireland).
Do gulls sing? In general, gulls are not known for their melodious voices. Their vocalizations are often brash and loud, part of the soundtrack of the beach in many locations. Their vocalizations are typically referred to as calls, with each species utilizing a variety of different calls for communicating things like finding (or begging for) food, warning off intruders, sounding a predator alarm to the colony, and other reasons. Different calls will also be used for pair-bonding and even during copulation. Chicks have different call sounds than adults.
See our previous post for more frequently asked questions about gulls.
Two new birds in the gull family Laridae join Birdorable this week! We've added the Pallas's Gull and the Western Gull to our cute cartoon bird family.
The Pallas's Gull is one of the largest species of gull in the world. It is a so-called "black-headed" gull because it is one of several species of gull that develops a fully black head during breeding season. An alternative name for this bird is the Great Black-headed Gull. They can weigh over four and a half pounds as full adults! Only the Great Black-backed Gull and Glaucous Gull average larger.
This bird is named after the prolific naturalist Peter Simon Pallas, who has several other species named in his honor, including Pallas's Cat, Pallas's Squirrel, and Pallas's Tube-nosed Bat.
The Western Gull is another large species of gull -- they can weigh in at three pounds or more. This is a "white-headed" gull found along the Pacific coast of North America. Western Gulls feed on the ocean, taking prey like squid, fish, and jellyfish on the surface since they are unable to dive. Western Gulls will also feed on carcasses of large marine mammals like sea lions, and opportunistically take food items like snails and starfish in intertidal habitats.
The San Francisco Giants have experienced problems with flocks of Western Gulls visiting their stadium in the late innings of baseball games. They presumably come to feed on refuse left in the stands by fans, but before the game is over flocks visiting the park poop on fans and swarm the playing field. The native birds are protected by federal law, although the Giants could get the gulls to disperse with the help of a falconer.
Larophile is available via our Zazzle shop on many different t-shirt styles and colors for men, women and children. You can see a selection of the apparel and other gift items available with this design at the bottom of this post, or click here to see them all.
This week, we're celebrating gulls! There are about 55 widely recognized species of gull in the world. We'd like to share some of the extreme facts and interesting statistics found within this diverse family.
Smallest Gull Species The Little Gull, weighing in at around 4.2 ounces (120 grams), is the smallest species of gull. Its length is 9.8 to 12 inches (25 to 30 cm).
Largest Gull Species The largest gull species in the world is the Great Black-backed Gull, which weighs in at around 62 ounces (1750 grams), almost 15 times as heavy as the Little Gull. It's length is 2.1 to 2.6 feet (64 to 79 cm).
The Longest Living Gulls Gulls, particularly the large "white-headed" gulls, can be long-lived. The longevity record for the European Herring Gull is 49 years! The longest-lived wild Great Black-backed Gull was over 27 years old.
Cross-Species Parenting The Black-headed Duck of South America is known to be a brood parasite of the Brown-hooded Gull. The duck lays eggs in nests of other birds (including other ducks and other gulls) and lets the nest-owners do the incubating! The ducklings are able to leave the nest just hours after hatching, making their escape without otherwise disturbing the nest. The Brown-hooded Gull or other nesting adult will continue to care for its own eggs and chicks.
Tale of the Tails Most species of gull have a rounded tail. There are only three exceptions: the Sabine's Gull and Swallow-tailed Gull have forked tails, and the Ross's Gull has a wedge-shaped tail.
Longest Migration Many species of gull are migratory. The Franklin's Gull may have the longest migration of all the gulls. They breed as far north as central Canada, and spend the winter as far south as Chile and Argentina.
Rare Gulls & Threatened Species The Lava Gull of the Galapagos Islands is considered to be Vulnerable to extinction. The small population of less than 400 pairs is relatively stable but the species is probably the rarest of all the gulls.
The Black-billed Gull of New Zealand is considered to be Endangered. The population has been on a rapid decline since the introduction of invasive predators to New Zealand, like weasels and cats.
Most Abundant The Ring-billed Gull was once hunted for its feathers. With protection the species has rebounded and is likely the most common species of gull in North America.
Night Vision The Swallow-tailed Gull is a "black-headed" gull found in the Galapagos Islands. They are the only completely nocturnal gulls in the world! They feed on squid and fish that only come to the water's surface at night. In order to be able to see in the dark, the Swallow-tailed Gull has very large eyes -- larger than any other gull species!
Join us in the following days as we celebrate all things gulls with our second Gull Week! Our first Gull Week was back in 2015. Gulls are part of a widespread family of social and intelligent seabirds.
Birdorable has 23 species of gull so far, out of the approximately 55 recognized species of gull in the world. We'll add a couple more this week to make it a cool 25!
To kick off the week, let's take a look back at how we've featured gulls here at Birdorable in the past:
Since our first Gull Week, we've added a couple of new species to the family. Check out our Grey-hooded Gull and Iceland Gull. We hope you'll join us this week as we celebrate gulls on the Birdorable blog!