Black Tern Diet and Size: Feeding Habits, Predators, and Measurements
Black Terns used to have a large breeding population in the UK centred around the fenlands of East Anglia. Sadly as these wetland habitats were drained for agricultural development, the Black Tern population all but died out.
Nowadays, they are only passage migrants that can be seen as they travel to and from their African and South American wintering grounds and their Continental European breeding grounds. In this article we’ll be looking at the eating habits, breeding habits as well as the size and weight of these interesting freshwater Terns and much more.
Table of Contents
The Dietary Habits Of The Black Tern
Black Terns (Chlidonias niger) have a varied diet that changes with the season and the availability of food.
What Does A Black Tern Eat?
The diet of the Black Tern mainly consists of flying insects including; dragonflies, mayflies, beetles, and flies. They typically catch these insects mid-air or snatch them from the water’s surface.
During the breeding season, they may catch crustaceans, small molluscs, and other invertebrates from shallow waters.
They also consume small fish, especially outside the breeding season when they forage over lakes, rivers, or coastal waters.
What To Feed A Baby Black Tern?
Black Terns feed their chicks mainly insects and small fish. During the early stages of development, adults regurgitate partially digested food to feed their young, ensuring that the chicks receive a nutrient-rich diet that is easy to swallow.
As the chicks grow, parents bring whole prey, particularly; insects like dragonflies and mayflies are a large part of the chick’s diet. As the chicks develop, parents may also feed them small fish caught from nearby water bodies.
These protein rich foods are essential for the rapid growth and development of the chicks.
Breeding Habits Of Black Terns
The breeding habits of Black Terns are fascinating and include a range of behaviours that help strengthen pair bonds, select nesting sites, and protect their young.
One of the most distinctive behaviours during the breeding season is the aerial courtship displays. Pairs engage in synchronised, graceful flying where the male and female soar and swoop together, often high above their breeding habitat. This flight strengthens the pair bond and signals readiness for breeding.
The male will catch a fish or insect and present it to the female in mid-flight or at a nesting site. This ritual, known as courtship feeding, helps the female gauge the male’s ability to provide food for future chicks.
He will also perform various displays including bowing or offering nesting materials to the female.
Do Black Terns Mate For Life?
Black Terns do mate for life and form long-lasting pair bonds. However, there are cases where pairs change partners. This is particularly true if the nesting fails to produce any chicks or one partner dies.
The Size & Weight Of Black Terns
Both male and female Black Terns are similar in size and colouration making it difficult to distinguish between the sexes.
How Much Does A Black Tern Weigh?
An adult Black Terns weighs around 73 grams (2.5 ounces). This light weight enables the Black Tern to fly extremely long distances between their breeding grounds in Continental Europe and their wintering grounds in Africa and South America.
How Big Is A Black Tern?
The Black Tern has an overall length of around 22 to 24 cm and boasts a wingspan of around 64 to 68 cm. Despite their small size, Black Terns are agile fliers, known for their graceful, buoyant flight, especially when foraging or performing courtship displays.
Their compact size and light weight make them efficient hunters of insects and small fish.
Are Black Terns Under Threat?
Black Terns face several threats, from both natural and human causes. While they are not currently classified as endangered globally, they are considered near threatened or of conservation concern in certain regions due to huge declines in their population in some areas.
One of the biggest threats to Black Terns is the loss or degradation of their wetland habitats due to human activities like wetland drainage, pollution and changes in water levels due to water management practices.
Changes in climate can impact wetland ecosystems by altering water levels, increasing the frequency of storms, and causing droughts, all of which can harm Black Tern nesting sites and food sources.
Human disturbance due to recreational activities like boating and fishing as well as walking close to breeding colonies can disturb nesting birds. In some cases they can abandon nesting sites altogether leaving eggs and chicks vulnerable.
A shortage of food is another concern for the Black Tern population which can be caused by overfishing, pollution and the use of pesticides and insecticides.
What Eats A Black Tern?
Adult Black Terns as well as their chicks and eggs are also under the threat of predation by many predatory birds. Including; Herring Gulls, Great-Black Backed Gulls, Hawks and Crows.
They are also under threat from mammals including; foxes, raccoons, minks and otters. This is particularly when their nests are located on low easily accessible islands or in marshes with easy land access.
Fish can also take young chicks particularly large Pike and Largemouth Bass. Plus in some regions, water snakes also prey on eggs and chicks.
While Black Terns are agile and protective of their nests, their small size and reliance on fragile wetland ecosystems make them vulnerable to both natural predators and environmental changes.
Where Can I See Black Terns In The UK?
In the UK, Black Terns are mainly seen as passage migrants during their spring and autumn migrations. They do not breed in the UK, but instead pass through while travelling between their breeding grounds in northern and eastern Europe and their wintering grounds in Africa.
The spring migration typically peaks in late April and May when Black Terns are often seen along the southern and eastern coasts of England, though they can also be spotted inland near large water bodies.
However, you’re far more likely to spot Black Terns in the UK during the autumn migration in August and September.
The most reported sightings of Black Terns occur in the following places;
East and South Coasts of England
- The Suffolk Coast
- The Norfolk Coast
- The Kent Coast
- The Sussex Coast
Inland Reservoirs and Lakes
- Rutland Water (Leicestershire)
- Grafham Water (Cambridgeshire)
- Blashford Lakes (Hampshire)
Large Wetland Reserves
- RSPB Minsmere (Suffolk)
- Titchwell Marsh (Norfolk)
- Cley Marshes (Norfolk)
Although less common than in southern England, Black Terns are occasionally seen along the coasts of Scotland and Wales, particularly in areas with large lakes or coastal wetlands.
SEE ALSO: Ptarmigan Diet and Size: Feeding Habits, Predators, and Measurements
Frequently Asked Questions
Black Terns breed in freshwater wetlands, marshes, and shallow lakes across northern and eastern Europe, Asia, and parts of North America.
Black Terns primarily eat insects, small fish, and aquatic invertebrates.
Black Terns can be seen in the UK during their migration in spring (April-May) and autumn (August-October).
