Common Tern vs Arctic Tern: How to Tell Them Apart

Updated 6 October 2026

Quick answer. On summer adults, check the bill. A Common Tern has an orange-red bill with a black tip. An Arctic Tern has a shorter, all blood-red bill. On the ground, the Arctic Tern's legs are so short it seems to sit on its belly. Overhead, all its flight feathers let the light through. The Common Tern shows only a small pale patch.

Side by side

Feature	Common Tern	Arctic Tern
Size	Low to mid 30s cm long. Bulkier, with a longer head and bill.	Much the same length, but slighter, with a rounder head.
Bill	Longer. Orange-red with a black tip.	Shorter and finer. Dark blood-red, with no black tip.
Legs	Longer, red, easy to see on a standing bird.	Very short. The bird looks as if it is sitting down.
Key plumage	Pale grey above, whiter below. Late summer adults show a dark wedge on the outer upperwing.	Greyer below, so a white stripe stands out between the black cap and the grey chest. Upperwing evenly pale.
Underwing	Only the inner primaries are translucent. Broad, smudgy dark tips to the outer primaries.	All the flight feathers are translucent. A thin, sharp black line along the tips of the primaries.
Tail	Shorter streamers. On a perched bird they stop at about the wing tips.	Long streamers that reach past the wing tips.
Flight	Strong and steady. Head and bill stick well out in front.	Lighter and bouncier. Short necked. Often hovers in steps before diving.
Song	None. Calls only.	None. Calls only.
Call	A long, harsh "kree-arrr" that falls in pitch. Also a short "kip".	Higher and shorter: "kree-er". Also a hard, rattling "kt-kt-kt".
Habitat	Coasts and inland: gravel pits, reservoirs and rivers. Takes to nesting rafts.	Coasts and islands. Hardly ever nests inland in Britain.
When in the UK	Mid April to September, a few into October.	Late April and May to September.
UK status	Amber list. About 11,000 pairs (2015).	Red list. The commoner of the two in the UK, with most pairs in Scotland.

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The quickest way to tell them apart

If the bird is perched, look at the bill tip and the legs. A black tip and a clear length of red leg make it a Common Tern. An all red bill on a bird with almost no legs is an Arctic Tern.

If it is flying over you against a bright sky, look through the wing. On an Arctic Tern the whole outer wing glows, with a fine black line along the rear edge. On a Common Tern the outer wing looks darker, with a pale window only behind the bend.

By sight

Proportions. The Common Tern has a longer bill, flatter crown and longer neck, so more of the bird sits in front of the wings. The Arctic Tern is round headed and short necked, with more tail behind.
Upperwing. From midsummer, Common Terns show a dark wedge on the outer primaries where older feathers have worn. Arctic Terns stay clean silver-grey.
Juveniles. Young Common Terns have a ginger tone to the back, a dark bar on the front of the wing and an orange base to the bill. Young Arctic Terns look cleaner and greyer, with white rear wing feathers and a darker bill.

By sound

Both are noisy at colonies. The Common Tern's main call is a long, grating "kree-arrr" with the stress on the first part and a clear drop at the end. The Arctic Tern's version is higher, thinner and shorter, and it mixes in fast, hard, rattling notes when alarmed.

The difference is subtle, and mixed colonies make it harder. Check a phone recording in Sound ID.

By season and habitat

Both are summer visitors. Common Terns return from mid April. Arctic Terns peak a little later, in late April and May. The Arctic Tern makes the longest migration of any bird, to Antarctic waters and back. Common Terns winter off western and southern Africa.

Geography is a strong clue. Arctic Terns breed mainly in Scotland, above all in Orkney and Shetland, with colonies south to Northumberland, Anglesey and Northern Ireland. Common Terns breed round most coasts and far inland in England. A tern nesting on a gravel pit raft in the Midlands is a Common Tern.

The exception is spring passage. In late April and early May, flocks of Arctic Terns cross England and drop onto reservoirs, most often in rain or north-easterly winds. See our migration guide.

Common mistakes

Trusting bill colour in autumn. Both get darker bills after breeding, and juveniles of both have dark bills.
Assuming every inland tern is a Common Tern in spring. Check passage flocks with care.
Forgetting other terns. The Roseate Tern is rare, very pale, with a mostly black bill. The Sandwich Tern is bigger, with a black bill tipped yellow.

Where to see both

For Common Terns at close range, try the Scrape at RSPB Minsmere or watch the breeding birds at Rutland Water, a reservoir that can also catch Arctic Terns on spring passage. For nesting Arctic Terns you need to go north: the Farne Islands in Northumberland, reached by boat, hold a well-known colony. Our seabirds guide has more colonies.

FAQ

What is a commic tern?

It is birders' shorthand for a tern that is either Common or Arctic but was not seen well enough to say which. It is an accepted entry for distant or brief views.

Which tern nests inland in the UK?

The Common Tern. It breeds on gravel pits, reservoirs and rivers across lowland England, often on rafts put out for it. Arctic Terns are almost wholly coastal breeders, though migrants pass over inland waters in spring.

Do Arctic Terns attack people?

At the nest, yes. They dive at anyone who walks through the colony and will peck heads. On a visit to a colony, keep to the paths and wear a hat.

Log both terns

Common Tern and Arctic Tern are both in the Birdedex. Log the one you are sure of, and keep the commic terns in your notebook.

Open the Birdedex →