The Arctic tern belongs to the class Aves, which contains all birds. More specifically, the Arctic tern is in the order Charadriiformes and the family Laridae. Here is a quick outline of the classification:
Kingdom
Animalia – Arctic terns are animals.
Phylum
Chordata – Arctic terns are vertebrates with a backbone.
Class
Aves – This class contains all birds.
Order
Charadriiformes – This order contains the gulls, terns, auks, and skimmers.
Family
Laridae – The gulls and terns belong to this family.
Genus
Sterna – The terns belong to this genus.
Species
Sterna paradisaea – This is the binomial name for the Arctic tern.
So in summary, the Arctic tern belongs to the class Aves along with all other bird species. This places it in the phylum Chordata which contains all vertebrates. The specific order, family, genus, and species give additional information about how the Arctic tern relates to other similar birds.
Characteristics of the Class Aves
Since the Arctic tern belongs to the class Aves, it shares many key characteristics with other birds:
- Feathers – All birds have feathers which provide insulation and allow for flight.
- Beaks – Beaks are used for eating, grooming, feeding young, and defense.
- Wings – Wings provide powered flight which sets birds apart from other animals.
- Lightweight skeletons – Birds have hollow and lightweight bones which aid in flight.
- High metabolisms – Birds have very high metabolisms to support the energy demands of flight.
- Hard-shelled eggs – Birds lay eggs with hard calcite shells to protect the developing young.
- Warm-blooded – Birds are endothermic and maintain a high constant body temperature.
The Arctic tern exhibits all of these class Aves characteristics. Its streamlined body, long pointed wings, feathers, and forked tail all enable it to fly enormous distances as it migrates. Like other birds, the Arctic tern builds nests, lays eggs, and has a toothless beak. Its high metabolism powers it on its pole-to-pole migration.
Evolutionary History
Birds evolved from feathered theropod dinosaurs during the Jurassic period around 150 million years ago. They adapted powered flight through changes to their forelimbs and skeletal structure. Birds diversified rapidly and displaced pterosaurs as the main flying vertebrates.
The earliest seabirds evolved during the Cretaceous period. The Arctic tern lineage probably diverged from other terns around 30 million years ago during the Oligocene. By adapting to nesting and feeding in high latitude Arctic environments, the Arctic tern occupied an important niche.
Distinctive Features of Arctic Terns
While the Arctic tern shares the overall Aves body plan, it has many distinctive adaptations to its pelagic, predatory lifestyle:
- Long, narrow wings for endurance flight on migration.
- Streamlined and buoyant body to aid surface diving.
- Forked tail for aerial maneuverability.
- Pointed bill specialized for catching fish.
- Plumage differences between breeding and nonbreeding.
- Very short legs set far back on the body.
- Webbed feet for swimming and pushing off from the water’s surface.
- Salt gland to remove excess salt from the body.
The Arctic tern has distinct adaptations from other terns that allow it to migrate huge distances and utilize resources in the high Arctic. However, its core body plan places it firmly within the class Aves.
Reproduction
Arctic terns share the same reproductive strategies as other birds in the class Aves:
- Courtship behaviors like aerial displays and offering fish.
- Scrape nests on the ground with some sparse lining.
- Clutch size of 1-3 eggs which are incubated by both parents.
- Both parents feed the chicks after they hatch.
- Chicks fledge around 3-4 weeks after hatching.
These reproductive behaviors maximize breeding success and the ability to raise multiple young each season. The Arctic tern’s adaptations are aimed at taking advantage of the bounty of the Arctic summer to raise chicks before migrating south again.
Conclusion
In summary, the Arctic tern is a member of the class Aves, which means it shares key characteristics like feathers, wings, hard-shelled eggs, and flight with other birds. It diverged from a common seabird ancestor and evolved adaptations for its long-distance migratory lifestyle. However, features like its streamlined body, long pointed wings, salt gland, and migratory breeding behaviors place it firmly within the overall Aves blueprint. Understanding what class the Arctic tern belongs to provides insight into its evolutionary history, anatomy, reproduction, and lifestyle.