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

Black Terns are rare in the world of Terns as they are one of only three members of the Tern family that breed in freshwater marshes. They used to be a regular sight in the UK  up until the early 19th century. Especially in the Eastern fenlands of Lincolnshire and Cambridgeshire before the area was drained removing their breeding grounds which pretty much wiped out the English population by about 1840.

There have been attempts to reintroduce the Black Tern to the UK with only limited success. There were around 5 or 6 breeding pairs reported in England and one in Ireland during the 1970s.

Now they are regular migrants and often arrive during spring as they fly towards their continental breeding grounds and get blown off course by strong easterly winds. They are easily distinguishable from other Terns with their black head and underparts, and dark grey back and wings. 

In this article we’ll be taking a close look at the life cycle of the Black Tern from nest building to fledging and much more in between. Keep reading to find out more about these interesting members of the Tern family.

How Long Does A Black Tern Live?

The average lifespan of a Black Tern is around 10 to 17 years with some surviving in the wild for around 21 years according to ring data.

They reach sexual maturity at around the age of 2 years; this is common in birds that have relatively extended life expectancy.

How Fast Can A Black Tern Fly?

The Black Tern (Chlidonias niger) can reach speeds of up to 17 mph (28 km/h) when flying. They are known for their erratic and floaty flight, and are often seen hovering above marshland in search of food.

Are Black Terns Aggressive?

Black Terns are generally peaceful birds and are rarely aggressive towards other Black Terns. Having said that, they will enthusiastically protect their eggs, chicks and nests from predators.

This aggression is even displayed towards any humans that happen to stray too close to their nesting site. Black Terns will gang up with others nesting in the same area and mob any would-be predators. They are known to dive bomb in large groups and peck at any intruder.

What Is A Black Tern’s Habitat?

Black Terns typically nest in large freshwater marshes in small colonies. They can also be found in rice fields and on some river islands.

During their migration, Black Terns can be found in any number of different wetland habitats including; lakes, marshes, sewage lagoons, beaches and even open seawater. In winter they migrate to coastal areas of Africa and South America.

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

It doesn’t take very long at all for Black Terns to build a nest, in fact, in as little as 4 days the nesting site is selected, the nest constructed and the eggs laid.The male and female work together to build the nest which is typically built in shallow, still water in a position sheltered from the wind and any waves. 

The nest itself is constructed from bulrushes or cattails found floating on the surface of the water. The male and female Black Tern gather dead vegetation and arrange it into a shallow, floating mound with a bowl-shaped area in the middle.

These nests are typically built on floating dead vegetation, but are sometimes constructed on solid ground close to the water’s edge. The nests are generally constructed in sites with around 20 other nests forming a small colony which is useful for defending the nests against any would-be predators.

Eggs

Once the nest has been successfully constructed to the satisfaction of both birds, they move on to the next stage in the life cycle of the Black Tern, the egg laying phase.

When Do Black Terns Lay Eggs?

The typical breeding season for Black Terns runs from May to June. The exact time the eggs are laid can vary depending on factors such as geographical location, temperature, the abundance of food and the health and experience of the individual birds.

If the climatic conditions are favourable, the female might lay her eggs as early as the end of April. However, in cold springs egg laying might be delayed until late June or even early July.

How Many Eggs Does A Black Tern Lay?

The female will lay anywhere between 1 to 4 eggs with an average clutch containing 2 eggs. This small number of eggs makes it easier for the parents to successfully raise their younglings.

This is an essential factor in the survival of the species.

What Do Black Tern Eggs Look Like?

The eggs of the Black Tern are oval shaped and in some cases more pyriform (extremely pointed at one end). The colour varies from site to site and typically blends in with the colour of the nest. 

Eggs can vary in colour from an off-white, light buff or dark olive colour with dark brown markings that act as a perfect camouflage to keep the eggs relatively safe from predators.

How Long Do Black Tern Eggs Take To Hatch?

The eggs hatch after around 19 to 23 days of incubation. Both the male and female take turns incubating the eggs and flying off in search of food.

Their diet consists mainly of insects that fly above their freshwater habitats as well as fish and molluscs found in the water close to their nesting site.

Chicks

Once the incubation period has passed we move on to the next stage in the life cycle of the Black Tern, the chicks.

How Many Chicks Does A Black Tern Have?

The number of chicks that hatch should correspond to the number of eggs laid. However, this isn’t always the case, the average survival rate from egg to fledging is around 50%.

This means that from a clutch of 2 eggs, 1 will survive to the fledgling stage. There are various factors that can affect the survival rate of Black Tern chicks which include; the condition of the habitat, the amount of food available, the weather as well as attacks by predators.

When Do Black Tern Chicks Open Their Eyes?

Black Tern chicks have their eyes open as soon as they hatch. These precocial birds are relatively mature and mobile as soon as they hatch.

They are capable of leaving the nest and swimming within 24 hours of hatching. Both parents bring the younglings food for around 7 to 14 days while the chicks remain unable to fly.

When Do Black Tern Chicks Fledge?

Black Tern chicks develop at a steady rate and typically take their first flight (fledge) at about 23 days after hatching. Even after they fledge, the fledglings still rely on their parents for food for around 2 weeks.

During this time they are learning where to find food, what to eat and how to avoid predators.

SEE ALSO: Ptarmigan Diet and Size: Feeding Habits, Predators, and Measurements

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