Arctic Tern Vs Caspian Tern: Key Differences Explained

Arctic Tern Vs Caspian Tern: Key Differences Explained

It is easy to tell the difference between the Caspian tern and the Arctic tern because the Caspian tern is the largest tern in the world. It is also a rare visitor to the shores of the UK whereas Arctic terns are a relatively common sight from April to September.

Key Takeaways

  • Caspian terns are far larger than Arctic terns
  • Caspian terns have black (or dark grey) feet and legs whereas Arctic terns have red feet and legs
  • When flying, Caspian terns resemble gulls more than terns
  • Arctic terns are more slender and much smaller

What Is The Difference Between The Arctic Tern And The Caspian Tern?

There are several marked differences between the Arctic tern and the Caspian tern as well as a few similarities. Let’s take a closer look at these fascinating birds.

Visual Differences

Female Arctic Tern

The most striking visible difference between the Caspian tern and the Arctic tern is the size difference.  Caspian terns are large, heavy bodied seabirds with a large head as well as a thick pointed bill which is straight. 

They also have broad, long pointed wings and a shallow forked tail.

Whereas Arctic terns are far smaller and much more slender and have angular wings and long tail streamers.

Caspian terns are mainly white with pale grey upper wings. The Arctic tern on the other hand, is a more grey colour overall.

Arctic terns have red legs whereas Caspian terns have black or dark grey feet and legs.

When in flight, Caspian terns resemble the flight of a gull more than the flight of any other members of the tern family. With smooth wing beats as opposed to the familiar choppy flight of the smaller terns.

Differences In Habitat

Caspian terns breed in open flat areas around coastlines, beaches, on islands always near water. They can be found nesting near freshwater as well as in seawater areas.

In Winter, they stay mainly in coastal areas near to the sea although they can occasionally be found on freshwater lakes or rivers.

Arctic terns breed in the Arctic regions as well as many other places around the world including coastal areas of the UK.

They tend to fly south in the winter to the Antarctic regions travelling around 50 to 60 thousand miles every year.

Nests & Eggs

Both of these bird species make scrape nests by scraping the surface of the beach with their feet to make a small depression. The nest is made by both parents.

Caspian terns tend to ring their nests with pebbles, fragments of shell, driftwood and other objects found on the beach to help keep the eggs in and mark the boundary of the nest.

Both parents take turns incubating the eggs which are similar in colour between both species.  The eggs typically have spots and are disguised, resembling rocks to fit in with their natural setting. They tend to have a light blue, green, or grey shade. 

The clutch size is also similar with the mother of both Caspian and Arctic terns laying somewhere between 1 to 3 eggs.

The size of the bird is reflected in the size of the eggs with Arctic tern eggs being around 3.6 x 3.2 cm in size Whereas Caspian tern eggs are around 7.3 x 4.8 cm in size.

The chicks of both species are born with their eyes open like most ground nesting birds, and are able to walk almost immediately after hatching.

Bird Calls

Caspian Tern

Although they are both members of the tern family, these two birds have very different and distinctive bird calls.

Caspian terns make a raspy  “karh” sound which can often be heard when they’re in flight and is common around breeding grounds.

Arctic terns on the other hand, make a sharp, piercing sound as well as many high pitched cries which are used to communicate with their partners and deter intruders from their nests.

Size & Weight

As we have seen, Caspian terns are far larger than Arctic terns. Adult Caspian terns are around 47 to 54 cm in length with a wingspan of around 126 to 128 cm.

Arctic terns are around 32 to 35 cm in length with a wingspan of between 75 to 86 cm.

Caspian terns weigh around 530 to 785 g whereas Arctic terns are around 5 times lighter,weighing around 95 to 125 g.

When Can They Be Seen In The UK?

Arctic terns are regular visitors to the UK and can be seen from April to September. You can regularly see Arctic terns in coastal areas of Scotland and Ireland. There are large breeding colonies found in the Shetland and Orkney Islands.

There are also breeding colonies to be found off the Welsh Anglesey coast and on the Isle of Man.

Caspian terns are rare visitors to the UK but can sometimes be seen during the summer months. Sightings can sometimes be made off the east coast of Scotland as well as inland in Norfolk, Lincolnshire and parts of Yorkshire.

SEE ALSO: Arctic Tern Life Cycle: Nest Building To Fledging (and everything in between)

Frequently Asked Questions

What is the difference between a Caspian tern and an Arctic tern?

The main difference between the Caspian tern and the Arctic tern is the size. Caspian terns are the largest members of the tern family with adults being almost twice the size of adult Arctic terns. Caspian terns also have black legs and feet whereas Arctic terns have red feet and legs.

What are the characteristics of the Caspian Tern?

The characteristics of the Caspian tern are a large heavy body with a large head and a thick straight bill and a shallow forked tail.

What are the special features of the Arctic tern?

The special features of the Arctic tern include; its red bill, legs and feet, its angular wings and its ability to fly from the Arctic to the Antarctic every year.

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