Sandwich Tern Life Cycle: Nest Building To Fledging (and everything in between)

Sandwich Terns are summer visitors to UK shores and can be seen on sandy beaches and islands around the coastline. These relatively large Terns have whitish-grey upperparts, white underparts, a large black cap, a shaggy black crest, short black legs and a yellow-tipped black bill.

Outside of the breeding season they lose the shaggy black crest and their foreheads become white. When in flight, the Sandwich Tern shows grey wedges on their wing tips as well as a forked tail.

In this article we’ll take a close look at the Sandwich Tern particularly their nest building, egg laying and chick rearing habits. Keep reading to find out more.

How Long Does A Sandwich Tern Live?

The average lifespan of a Sandwich Tern is around 12 years and they typically start breeding at the age of 3 years. According to ring data, there have been isolated individuals that have survived for as long as 30 years and 9 months.

How Fast Can A Sandwich Tern Fly?

Sandwich Terns can fly at an average speed of anywhere between 25 to 30 mph (40 to 48 km/h). These speeds are pretty common among seabirds that rely on relatively fast speeds to catch prey or evade predators.

When hunting for food or during migratory flights, they may attain even faster flight speeds.

Are Sandwich Terns Aggressive?

Even though Sandwich Terns are the largest Tern species to breed in the UK, they are surprisingly non-aggressive. They tend to nest in colonies with other more aggressive species like Black-Headed Gulls and Arctic Terns.

These other more aggressive birds protect the nesting colony and in so doing, they protect the nests of the Sandwich Tern. If it becomes absolutely necessary, Sandwich Terns will show defensive behaviour by spreading their wings and raising their bodies to seem larger than they actually are.

They have also been seen displaying mobbing and dive bombing tactics to protect their nests and chicks.

What Is A Sandwich Tern’s Habitat?

Sandwich Terns prefer sandy beaches for nesting typically in large colonies which includes other seabirds like Arctic Terns and Black-Headed Gulls. However they will frequent sandy and rocky beaches, cliff sides, estuaries and large inland bodies of water like lakes and reservoirs.

Sandwich Terns are summer visitors and passage migrants and can be seen around the coastline of the UK from March until October. They then fly off to warmer African beaches to overwinter.

How Long Does It Take For A Sandwich Tern To Build A Nest?

It generally takes around 1 to 2 days for Sandwich Terns to build a nest. The nest is a simple scrape nest which is lined with the birds excrement.

The nest is sited on the ground just above the high tide mark away from any vegetation. Mating pairs will often abandon a nest if any growing vegetation encroaches on the site.

They nest in large colonies as there is safety in numbers. Colonial sites can be extremely noisy and if you stray too close you’re likely to get dive bombed by other species in the colony.

Eggs

Once the pair are satisfied with the siting and construction of the nest, they move onto the next stage in their life cycle, the eggs.

When Do Sandwich Terns Lay Eggs?

As the nest building takes such a short time, egg laying can commence within days or weeks of the bird’s arrival back to their breeding grounds. However, egg laying tends to begin during the first week of May unless the weather is particularly bad.

In which case egg laying is delayed until conditions are more favourable. Having said that, Sandwich Terns are typically the first species to finish their breeding season 

How Many Eggs Does A Sandwich Tern Lay?

Sandwich Terns tend to lay 1 to 3 eggs per brood and they only lay one brood per season. A typical clutch contains 1 or 2 eggs but 3 isn’t impossible. 

This small number of eggs ensures that the parents can take care of their offspring and nurture them to adulthood.

What Do Sandwich Tern Eggs Look Like?

The eggs of the Sandwich Tern are white, pinkish or buff coloured and covered with dark brown speckles. They are oval shaped and around 51 x 36 mm in size.

The average weight of a Sandwich Terns egg is around 35 grams.

How Long Do Sandwich Tern Eggs Take To Hatch?

The eggs are incubated by both parents for around 21 to 29 days. The incubation period begins as soon as the last egg has been laid. The female will typically lay one egg each day until her clutch of 1 to 3 eggs is complete.

Chicks

Once the eggs hatch we move on to the next stage in the life cycle of the Sandwich Tern, the chicks.

How Many Chicks Does A Sandwich Tern Have?

Sandwich Terns generally have the same amount of chicks as eggs laid which in most cases is 1 or 2 chicks per brood. There are occasions when the eggs aren’t fertilised or the embryo dies in the egg.

However, in most cases the number of chicks that hatch corresponds with the number of eggs laid. 

When Do Sandwich Tern Chicks Open Their Eyes?

Sandwich Tern chicks are precocial and have their eyes open as soon as they hatch. They are also ready to leave the nest after around 24 to 48 hours of hatching.

Having their eyes open as soon as they hatch is a survival trait which ensures that they are able to recognise their parents and respond quickly to movements and calls from their parents.

When Do Sandwich Tern Chicks Fledge?

After around 7 to 14 days some colonies form creches where young birds can gather together in large flocks when their parents are away hunting for food.

These large groups offer some protection from predators simply by their sheer size and number of chicks in one place. The chicks develop and grow at a relatively fast rate and are usually ready to take their first flight or fledge at around 28 to 35 days after hatching.

Even after fledging, the young Sandwich Terns spend the following year shadowing their parents learning how and where to catch prey. As well as dodging any predators.

SEE ALSO: Black Grouse Vs Capercaillie: Key Differences Explained

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