Sandwich Tern Diet and Size: Feeding Habits, Predators, and Measurements

Sandwich Terns are the largest Tern species we get here in the UK and they can easily be identified by their black crest during the breeding season. They are pretty much the same size as the Black-Headed Gull and relatively common seabirds with an estimated 14,000 breeding pairs visiting the UK every year.

They often nest in large colonies with other seabirds like Black-Headed Gulls and Arctic Terns. These other seabirds are far more aggressive than Sandwich Terns and they rely on that aggression for their protection when nesting.

To find out more about these fascinating summer visitors, keep reading.

The Dietary Habits Of The Sandwich Tern

Sandwich Terns catch their prey by plunge diving underwater.

What Does A Sandwich Tern Eat?

The diet of the Sandwich Tern mainly consists of fish. They mainly eat sand eels, sprats, herring and whiting. They will also supplement their diets with squid and small crustaceans occasionally but their main food source is fish.

What To Feed A Baby Sandwich Tern?

The parents will catch small fish which they carry back to the nest crosswise in their bills making them visible as they fly towards their nests. They will feed their chicks with these small fish by placing them directly into their bills.

The parents make frequent trips to and from the nest with small fish to keep supplying the chicks with high protein food. This enables the chicks to grow at a fast rate. The chicks are generally ready to fledge the nest after around 3 to 4 weeks. 

However, they remain with their parents for around 10 to 12 months learning migratory routes, how and where to find fish and other foodstuffs and the best ways to avoid predators.

Breeding Habits Of Sandwich Terns

Male Sandwich Terns often perform elaborate aerial displays in order to attract female mates. They fly with rapid wing beats while calling loudly to attract a female.

These ritualistic displays can often involve group displays where several males will all perform at the same time. Once a male and female pair up which is cemented by the male offering the female small fish which she accepts, the pair will preen each other.

This mutual preening is an important part of their relationship bonding process.

Do Sandwich Terns Mate For Life?

Although many Sandwich Terns don’t mate for life, their pair bonds can last for 3 or 4 seasons. However, they do remain monogamous during the season once they have paired up.

Having said that, in some cases paired males will attempt to mate with additional females.

The Size & Weight Of Sandwich Terns

Sandwich Terns are very similar in size to Black-Headed Gulls except that Sandwich Terns have that black crest during the breeding season. 

How Much Does A Sandwich Tern Weigh?

Male and female Sandwich Terns tend to look very similar in appearance. However, males tend to be the larger of the two which can make it easier to sex these seabirds. The average weight of an adult Sandwich Tern is around  210 to 260 grams.

How Big Is A Sandwich Tern?

The Sandwich Tern is the largest Tern we see in the UK with an average adult being around 36 to 41 cm in length and boasting a wingspan of around 95 to 105 cm.

Are Sandwich Terns Under Threat?

While they are not currently considered to be a threatened species, Sandwich Terns face various threats to their well being. These threats include; habitat loss particularly through coastal development, tourism and climate change.

They are also susceptible to pollution from oil spills to plastic debris which can affect their habitat and food supplies. Overfishing is another cause for concern for the food resources needed by Sandwich Terns.

Many Sandwich Tern colonies are located on protected sites where human access is restricted during the breeding season. This helps to maintain their numbers but ongoing monitoring and research is needed to help track their numbers and health.

They also face the threat of predators.

What Eats A Sandwich Tern?

Sandwich Terns are at threat from Peregrine Falcons, Herring Gulls and Great Black-Backed Gulls who will take adults, chicks and eggs. The nests are susceptible to raids from foxes, rats, weasels, stoats and other small mammals who will take eggs and chicks and in some cases adult birds as well.

Where Can I See Sandwich Terns In The UK?

Sandwich Terns can be seen at many coastal locations around the UK during the spring and summer months. After the breeding season they can be spotted on many beaches as they prepare to migrate to their West African wintering grounds.

Some of the most reported sightings occur in the following places;

Norfolk

• Blakeney Point
• Holkham National Nature Reserve

Suffolk

• RSPB Minsmere
• Havergate Island

Hampshire

• Langstone Harbour

Dorset

• Brownsea Island

Northumbria

• The Farne Islands

Cumbria

• South Walney Nature Reserve

Scotland

• Nigg Bay, Cromarty Firth

The above locations offer some of the best chances of observing Sandwich Terns in the UK. The best chances of sightings are during the breeding season and just before the autumn migration.

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