Black-bellied Tern
Sterna acuticauda
Visual Identification
Appearance
The Black-bellied Tern is a medium-sized tern with distinctive colouration. In breeding plumage, it has a black cap and belly, contrasting with its pale grey upperparts, white throat, and darker grey wings. The bill is yellow-orange, and the legs are reddish-orange. The underwings show a striking white pattern with a darker band across the flight feathers.
Non-breeding adults have a white forehead (streaked with black), belly, and a black band behind the eye. The bill develops a black tip during this period. Juveniles can be distinguished by their reddish bill base and blackish feet, along with darker markings than similar species.
Size
Length
32cm to 35cm
Wingspan
64cm to 68cm
Weight
90g to 150g
Colours
Males and females have similar plumage
Primary Colour
Grey Black White
Secondary Colour
Red
Beak Colour
Red Black Orange
Leg Colour
Red
Habitat and Distribution
Habitats
Woodland
Garden
Wetland
Coastal
Urban
Farmland
Grassland
Desert
Tundra
Rainforest
Mountain
Savanna
Distribution
Black-bellied Terns inhabit large rivers, lakes, and coastal areas across South and Southeast Asia. They are found in countries such as India, Bangladesh, Myanmar, and Cambodia. These birds prefer freshwater habitats but may also frequent estuaries and coastal lagoons.
During the non-breeding season, some populations move to coastal areas or undertake short-distance migrations within their range following changing water levels and food availability.
Elevation Range
Up to 730 meters
Climate zones
Tropical, Subtropical
Distribution Map
This map gives you a rough idea of where you might spot a Black-bellied Tern. The coloured areas show countries where these birds have been seen.
A few things to keep in mind:
- Birds might not be everywhere in the coloured areas, for example, they may be present around the coast of that country
- Where birds live can change with seasons and available food
- This map is quite simple - it doesn't show exact locations
We're working on making our maps even better! Soon, we hope to show you:
- More detailed maps for bigger countries, including state and region
- How birds move around during different seasons
Behaviour and Ecology
Bird Attributes
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Share your thoughtsBird Attributes Explained
Our bird attributes system rates various aspects of a bird's capabilities on a scale of 0-100, based on data from field observations, scientific studies, and expert knowledge.
Attribute Categories:
- Agility: Manoeuvrability, speed, and grace in flight or movement.
- Strength: Physical power, often correlating with size and hunting abilities.
- Adaptability: Ability to thrive in various environments or changing conditions.
- Aggressiveness: Territorial behaviour and assertiveness, particularly during breeding seasons.
- Endurance: Stamina, often seen in migration patterns or foraging behaviours.
Understanding the Ratings:
- 0-20: Very Low
- 21-40: Low
- 41-60: Average
- 61-80: High
- 81-100: Very High
Remember, these attributes are relative to other bird species and don't necessarily indicate superiority.
Hover over the icon next to each attribute for more information.
Tap the icon next to each attribute for more information.
Agility
Reflects the bird's manoeuvrability, speed, and grace in flight or movement.
The Black-bellied Tern demonstrates remarkable agility through its precise plunge-diving technique, low-altitude flight patterns, and ability to hover effectively whilst hunting. Their forked tail provides excellent manoeuvrability, particularly when making quick directional changes during fishing.
Strength
Indicates the bird's physical power, often correlating with size and hunting abilities.
Whilst capable of carrying fish prey and maintaining steady flight in varying conditions, the Black-bellied Tern's relatively modest size (90-150g) and slender build suggest moderate strength. Their ability to plunge-dive effectively requires some muscle power, but they're not notably strong compared to other waterbirds.
Adaptability
Represents the bird's ability to thrive in various environments or changing conditions.
These terns show good adaptability through their ability to utilise both freshwater and coastal habitats, adjust to seasonal changes, and modify their hunting techniques (including following fishing boats). They can nest on various substrates, including floating vegetation, demonstrating flexible behaviour.
Aggressiveness
Measures the bird's territorial behaviour and assertiveness, particularly during breeding seasons.
During breeding season, Black-bellied Terns display territorial behaviour and will actively defend their nesting sites. They're known to produce harsh alarm calls when threatened and will mob potential predators, though they're not among the more aggressive tern species.
Endurance
Reflects the bird's stamina, often seen in migration patterns or foraging behaviours.
Their capacity for sustained low-altitude hunting flights, ability to migrate short distances, and regular plunge-diving activities demonstrate good endurance. They can maintain speeds of up to 40 km/h while hunting and spend considerable time airborne searching for prey, indicating strong stamina.
Diet
Black-bellied Terns primarily feed on small fish, which they catch by plunge-diving into water. They also consume aquatic insects, crustaceans, and occasionally small amphibians.
These terns often follow fishing boats to catch discarded fish or those stirred up by nets.
Behaviour
Black-bellied Terns are often seen flying low over water, scanning for prey. They hover briefly before plunge-diving to catch fish.
These terns are generally social, forming small flocks during non-breeding seasons and often associating with other tern species at roosting sites.
Vocalisation
The Black-bellied Tern's call is a harsh, grating 'kree-ah' or 'kik-kik'. During the breeding season, they become more vocal, producing a series of rapid, high-pitched notes that sound like 'ki-ki-ki-ki'. When alarmed, they emit a sharp, piercing 'keeya' call.
Nesting & Breeding
Breeding occurs primarily during the dry season when river levels are low. Black-bellied Terns form monogamous pairs and nest in small colonies, often with other tern species. They select sandy or rocky islands in rivers or lakes for nesting.
Nests are simple scrapes in the ground, sometimes lined with small pebbles. The female typically lays 2-3 eggs, which are pale buff with dark brown spots. Both parents share incubation duties.
Incubation lasts about 21-22 days, and chicks fledge after 25-30 days. Parents continue to care for the young for several weeks after fledging.
Conservation and Status
Global Conservation Status
The Black-bellied Tern is classified as Endangered due to rapid population decline. Major threats include habitat loss, water pollution, and disturbance of nesting sites.
Conservation efforts focus on protecting riverine habitats and raising awareness among local communities about the importance of these birds.
Birdwatching Tips
- Look for Black-bellied Terns near large rivers, lakes, and coastal areas
- Observe their distinctive low flight and hovering behaviour over water
- Listen for their harsh, grating calls during breeding season
- Watch for their unique plunge-diving feeding technique
Additional Information
Quick Facts
Family:
LaridaePredators
Main predators include large birds of prey, such as eagles and falcons, as well as corvids, gulls, and some mammals that may raid nests.
Did You Know?
- Black-bellied Terns are excellent swimmers, despite rarely being seen on water.
- They have been known to nest on floating vegetation in some areas.
- These terns can fly at speeds of up to 40 km/h when hunting.
References
- 1 2 3
website: BirdLife International. 2022. Sterna acuticauda. The IUCN Red List of Threatened Species 2022: e.T22694711A207933556.
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