Species Profile
Black-bellied Tern
Sterna acuticauda
Quick Facts
Conservation
ENEndangeredLength
32–35 cm
Weight
90–150 g
Wingspan
64–68 cm
Migration
Partial migrant
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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.
Identification & Characteristics
Colors
- Primary
- Grey
- Secondary
- Red
- Beak
- Red
- Legs
- Red
Attributes
Understanding Attributes
Rated 0–100 based on research and observation. A score of 50 is average across all bird species. These attributes are relative and don't necessarily indicate superiority.
Habitat & 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.
Distribution
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.
Calls & Sounds
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
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
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.
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