Arctic Tern Vs Common Tern: Key Differences Explained

Arctic Tern Vs Common Tern: Key Differences Explained

Due to their many similarities it can be difficult to tell the Arctic tern and the common tern apart. This is especially true when viewing these fascinating birds from a distance.

However, there are certain distinguishing features that will help in the identification process. In this article we’ll be looking at those small but noticeable differences, helping you to differentiate between the two species.

Keep reading to find out more.

Key Takeaways

  • Arctic terns have a blood red somewhat spiky bill
  • Common terns have a more orange-red bill which is longer
  • Arctic terns are a pale grey colour whereas common terns are darker
  • Arctic terns have a light grey belly whereas a common terns belly is a much lighter grey
  • Arctic terns legs are a dark red colour whereas common terns legs are more of an orange-red colour
  • Arctic terns have narrower wings and longer tail streamers than common terns
  • Arctic terns are more slender with a smaller, rounder head

What Is The Difference Between The Arctic Tern And the Common Tern?

One of the main reasons why it can be tricky to tell these two birds apart is the fact that they often arrive at their breeding grounds at the same time. Or at least arrive within a short time of each other.

But that doesn’t mean that it’s impossible to tell them apart, because there are a few tell-tale signs if you know what to look for. These include;

Visual Differences

Female Common Tern

The first place to look is at the bill of the bird, Arctic terns have a relatively short, spiky bill which is blood red in colour. Whereas common terns have a longer bill which is a more orange-red colour and has a dark tip.

Then there’s the difference in the colour of these two birds, Arctic terns are a pale grey colour. Whereas common terns tend to be a darker, duskier grey.

Arctic terns tend to have a light grey belly. Whereas common terns tend to have a much paler grey belly.

The shape differences between these birds is another good identification feature. Arctic terns are more slender with a smaller rounder looking head. Common terns are larger and far more bulky in appearance.

If you spot a group of terns and you’re not sure which species they are, look at their legs. Arctic terns have far shorter legs than common terns.

Added to which, the leg colouring is slightly different as well. Arctic tern’s legs are a dull red colour. Whereas common tern’s legs are a more orange-red colour.

You’re more likely to be trying to identify these birds when in flight from a distance, which can be more of a challenge. However, Arctic terns tend to have narrower wings and much longer tail streamers than those of the common tern.

Plus common terns have dark streaked wingtips which can be strikingly different to the silvery grey wingtips of the Arctic tern. The outer wing of the Arctic tern appears to be translucent when in flight.

Differences In Habitat

Common terns can be found in many different habitats including rocky islands, salt marshes, barrier beaches and open waters. They breed throughout Europe, Asia and North America and spend their winters in warmer coastal tropical and subtropical areas.

Arctic terns breed in the Arctic regions as well as many other places throughout the world including the coastal areas of the UK. They winter in the Antarctic which means these amazing little terns can travel around 44,000 to 59,000 miles each year!

Nests & Eggs

Female Arctic Tern

Both Arctic terns and common terns are ground nesting birds. They both scrape out a shallow depression in the ground which is then lined with whatever they can find washed up on the beach or local plant material.

If they can’t find anything to line the nest with, the mother will lay her eggs on the shingle/gravel/sand. She will often place larger stones or grass or drift wood around the rim of the nest to prevent the eggs from rolling out.

Both parents take turns incubating the eggs which are pretty much identical in colour and markings for both species. The eggs are a dark olive colour with numerous brown spots or freckles.

The clutch size varies but it’s more likely that the common tern will lay a round 1 to 4 eggs whereas the Arctic tern is more likely to lay around 1 to 3 eggs.

Arctic tern eggs are around 3.6 x 3.2 cm in size, whereas common tern eggs are around 4.2 x 3.1 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

Although both members of the tern family, the common tern and Arctic tern have different and distinctive bird calls. The call of the Arctic tern is sharp and piercing and they make lots of high pitched cries to communicate with their mates and frighten intruders away around the nest site.

Common terns are also known for their vocal and social performances. They make a wide range of calls which are of a lower pitch compared to those of the Arctic tern.

Size & Weight

Arctic terns tend to be slightly smaller than common terns. Arctic terns have an average length of anywhere between 32 to 35 cm and a wingspan of between 75 to 86 cm.

Common terns are of a similar length with a slightly longer wingspan of between 77 to 98 cm.

However, common terns tend to weigh more than Arctic terns. Common terns weigh anywhere between 90 to 150 g whereas Arctic terns weigh anywhere between 95 to 125 g.

When Can They Be Seen In The UK?

Male Arctic Tern

Both the common tern and the Arctic tern can be seen in the UK from April to September. 

Arctic terns breed mainly in coastal areas of Scotland and Ireland with large colonies found in the Shetland and Orkney Islands. They also breed around the Welsh islands off Anglesey as well as on the Isle of Man.

Common terns also can be found in coastal areas of Scotland and are often spotted on lochs and islands on the west coast. As well as the Outer Hebrides, Northern Isles and around the Moray Firth.

In England, common terns can often be spotted on and around lakes and reservoirs all over lowland Britain. With many concentrated at river estuaries and coast lines.

Once the weather starts to turn around the middle to end of September they leave the UK and fly to their wintering grounds.

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

Frequently Asked Questions

How do you identify an Arctic tern?

You can identify an Arctic tern by its blood red bill and dark red legs.

Where can I see Arctic terns in the UK?

You can see Arctic terns in the UK mainly in coastal areas of Scotland and Ireland with large colonies found in the Shetland and Orkney Islands. They also breed around the Welsh islands off Anglesey as well as on the Isle of Man.

Where do common terns go in winter?

Common terns leave the UK in September and fly to warmer wintering grounds that stretch from the Spanish coast to the west coast of Africa.

Leave a Reply

Your email address will not be published. Required fields are marked *