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10 Fascinating Facts About the Black-naped Tern

The world of birds is a colorful and fascinating one, filled with unique and interesting species that capture our imagination. In this article, we will be exploring the Black-naped Tern (Sterna sumatrana), a bird that dazzles with its striking plumage and graceful flight.

Originating from Southeast Asia, this species has captured the hearts of bird watchers and enthusiasts alike with its unique characteristics and behaviors. Join us as we delve into the world of the Black-naped Tern and discover what makes it so special.

Identification

Field Identification

The Black-naped Tern is a small bird, measuring between 33 and 38 cm in length with a wingspan of 76-81 cm. It has a distinctive black nape (the back of the neck), which sets it apart from other terns.

Its upperparts are a pale grey, while its underparts are white. The bill and legs are black, and it has a black band on the tail.

When in flight, this species has a graceful, buoyant appearance, with deep wingbeats and occasional glides. It flies with its head held level with its body, giving it a streamlined appearance.

Similar Species

The Black-naped Tern can be easily confused with other tern species, such as the Common Tern (Sterna hirundo). However, the Black-naped Tern’s distinctive black nape provides a clear identifier.

Additionally, the Common Tern has a thinner, more pointed bill, and a more pronounced white forehead. Other tern species, such as the Roseate Tern (Sterna dougallii) and the Little Tern (Sternula albifrons), also have distinctive characteristics that differentiate them from the Black-naped Tern.

Plumages

The Black-naped Tern has two plumages: breeding and non-breeding.

Breeding Plumage: During the breeding season, the Black-naped Tern’s upperparts have a darker grey hue, and its crown and nape turn blacker. It also develops black stripes under each eye.

Non-breeding Plumage: During the non-breeding season, the Black-naped Tern’s upperparts become paler in color, and its crown and nape turn grey. The black stripes under each eye disappear, and the bird’s throat turns whiter.

Molts

The Black-naped Tern goes through two molts in a year: a complete molt and a partial molt. Complete Molt: The complete molt occurs after the breeding season, around November or December.

During this molt, the bird loses all its feathers and regrows new ones. Partial Molt: The partial molt occurs after the non-breeding season, around May or June.

During this molt, the bird only replaces some of its feathers.

Conclusion

The Black-naped Tern is a beautiful species of bird, unique in its striking plumage and graceful flight. Its distinctive features make it easy to identify, and its molting habits add an extra layer of interest to this fascinating species.

Whether you are a bird watcher or just someone with an appreciation for the natural world, the Black-naped Tern is a species worth learning about and observing in the wild. , as the article will end organically after covering the information in a thorough and informative manner.

Systematics History

The Black-naped Tern, Sterna sumatrana, falls under the family of Laridae, along with other terns and gulls. Systematic history describes the changes in classification of the Black-naped Tern, from its first recorded observations in 1817 in the Malayan Archipelego, to todays classification of the two subspecies, Sterna sumatrana sumatrana and Sterna sumatrana albistriata.

Geographic Variation

The Black-naped Tern has a longitudinal range that spans from the Red Sea to the Malay Peninsula and western Indonesia. Its breeding range is from the Nicobar Islands in the Bay of Bengal to the coasts of Japan and China.

The non-breeding range is more extensive, from the coasts of East and Southeast Asia down to Eastern Australia and the Solomons.

Subspecies

There are two subspecies of the Black-naped Tern: Sterna sumatrana sumatrana and Sterna sumatrana albistriata. Sterna sumatrana sumatrana is found in the North Arabian Sea, the Bay of Bengal and Southeast Asia.

This subspecies has a white forehead and is smaller in size compared to the other subspecies. Sterna sumatrana albistriata is found in Australia, the Philippines and Indonesia, and is larger in size compared to Sterna sumatrana sumatrana.

This subspecies has a grey forehead compared to the white forehead of the other subspecies.

Related Species

The Black-naped Tern has close relatives that belong to the genus Sterna, which consists of around 40 species. Its closest relative is the Bridled Tern, Sterna anaethetus.

These two species share several distinct characteristics, including a similar shape and coloration. The Bridled Tern is, however, larger in size and has a more extensive geographic range, spanning from the Red Sea to the Pacific Ocean.

Historical Changes to Distribution

The Black-naped Tern’s distribution has undergone significant changes since its first recorded observations in 1817. In the early 20th century, the species was considered a common sight along the coasts of the Indian subcontinent.

However, by the mid-20th century, populations had declined significantly due to habitat destruction and hunting. In the 1960s, the Black-naped Tern was even considered extinct in the Maldives, Mauritius and other small islands in the Indian Ocean.

As conservation efforts improved in the late 20th century, populations of the Black-naped Tern began to recover. Today, the species is considered a common sight along its breeding and non-breeding ranges.

However, habitat loss and pollution continue to be major threats to the species, with oil spills and plastic pollution being particularly problematic. One notable change in the Black-naped Tern’s distribution is the species’ expansion to new areas.

In the late 20th century, the Black-naped Tern began to establish breeding colonies along the coast of Western Australia, where it had not previously been observed. This expansion has been attributed to climate change and increased water temperatures, which have created new habitats suitable for the species.

Conclusion

In conclusion, the Black-naped Tern is a fascinating species with a rich history and evolving distribution. The species has gone through significant changes since its first recorded observations, from declines in populations to expansion to new areas.

While conservation efforts have helped the species recover in some areas, ongoing threats such as habitat destruction and pollution continue to be major challenges to the Black-naped Tern’s survival. By understanding the species’ systematics and history, we can better appreciate the unique characteristics of the Black-naped Tern and work towards protecting it for future generations.

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Habitat

The Black-naped Tern can be found in a variety of coastal habitats, including rocky and sandy shores, coral reefs, and tidal mudflats. The species prefers areas with low vegetation cover, as this allows for easy access to nesting sites.

The Black-naped Tern is also known to nest on small sandy islands and man-made structures such as jetties and offshore platforms. During the non-breeding season, the Black-naped Tern can be found in a range of habitats outside of its breeding range, including estuaries, coastal lagoons, and bays.

The species can also be seen patrolling offshore waters in search of food.

Movements and Migration

The Black-naped Tern is a migratory species, with populations in the northern part of its range migrating southward during the non-breeding season. The southern populations do not migrate at all.

The species is generally considered to be a short-distance migrant, although some individuals have been observed making longer migrations from the Philippines to Japan. The migration routes of the Black-naped Tern vary depending on the population.

Populations in the northern part of the range, such as in Japan and China, migrate southwards to Southeast Asia, Australia and the Solomon Islands. These populations typically begin their migration in late August and early September, and return to their breeding grounds in March or April.

Populations in the southern part of the range, such as those found in Southeast Asia and the Philippines, do not migrate at all. These populations remain in their breeding range year-round.

The Black-naped Tern’s migration patterns are influenced by a range of environmental factors, including food availability, weather patterns, and tidal cycles. Populations in the northern part of the range are known to follow certain tidal patterns in order to maximize their feeding opportunities during migration.

During migration, the Black-naped Tern can be found in a range of habitats, including offshore waters, coral reefs, and estuaries. The species is known to roost on small offshore islands during migration, and these roosting sites can attract thousands of individuals at once.

Conclusion

In conclusion, the Black-naped Tern is a migratory species that is adapted to a range of coastal habitats. During the breeding season, the species prefers low vegetation cover and can be found nesting on small islands and man-made structures.

During the non-breeding season, the species can be found in a range of habitats near the coast, including estuaries and coastal lagoons. The Black-naped Tern’s migration patterns are influenced by a range of environmental factors, including food availability, weather patterns, and tidal cycles.

Populations in the northern part of the range migrate southwards during the non-breeding season, while populations in the southern part of the range remain in their breeding range year-round. Understanding the Black-naped Tern’s movements and habitat preferences is vital for ensuring its conservation and protection, both within its breeding and non-breeding ranges.

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Diet and Foraging

Feeding

The Black-naped Tern is primarily a pelagic, plunge-diving species that feeds on small fish, squid, and crustaceans. The species can be seen patrolling offshore waters in search of food during the non-breeding season.

During the breeding season, the species forages closer to its nesting sites, within 20 km of the coast. The Black-naped Tern hunts for its prey by diving into the water from the air at high speeds.

It also occasionally hovers above the water’s surface before diving, allowing it to get a better view of the prey below. The species hunts alone or in small groups and can be seen diving to depths of up to 10 meters.

Diet

The Black-naped Tern has a diverse diet that primarily consists of small fish such as anchovies, sardines, and mackerels. The species also feeds on squid and crustaceans such as prawns and crabs.

Studies have shown that the species can consume up to 31 fish per hour during the breeding season, with an average prey size of 4.75 cm.

Metabolism and Temperature Regulation

The Black-naped Tern has a high metabolism that allows it to sustain the energy demands of its plunge-diving feeding behavior. These feeding behaviors have been shown to increase the birds’ metabolic rate by up to 10 times their resting metabolic rate.

Additionally, the Black-naped Tern has developed strategies to regulate its body temperature during feeding. The species has a network of blood vessels in its bill that allow it to dissipate the heat generated during the diving process.

This adaptation helps to prevent overheating when diving into the warm ocean waters.

Sounds and Vocal Behavior

Vocalization

The Black-naped Tern is a vocal bird with a range of calls used for communication. During the breeding season, the species has a repertoire of calls used for courtship and territorial displays.

One of the most distinctive calls of the Black-naped Tern is its high-pitched trill, which is often used during courtship displays. The species is known to call in flight, with pairs engaging in coordinated vocalizations during aerial displays.

These vocal displays can be seen during courtship, territorial displays, and feeding behaviors. Additionally, the Black-naped Tern has been observed producing calls in response to threats or disturbances, such as the presence of predators or human disturbances.

These calls are often loud and sharp, and can be used to alert other members of the flock to potential dangers.

Conclusion

In conclusion, the Black-naped Tern is a species with unique feeding behaviors and vocalizations. The species feeds primarily on small fish, squid, and crustaceans, and has developed unique adaptations to support its high metabolism and regulate body temperature during feeding.

The species is also highly vocal, using a range of calls for communication and display during courtship, territorial displays, feeding behaviors, and response to threats or disturbances. Understanding the Black-naped Tern’s feeding behaviors and vocalizations is important for its conservation and protection, as it allows us to better understand the species’ behavior and the threats it faces in the wild.

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Behavior

Locomotion

The Black-naped Tern exhibits aerial locomotion during its foraging, courtship, and territorial displays. This species is an agile and fast flyer, with deep, powerful wing beats interspersed with glides that allow it to cover large distances in search of food.

During courtship displays, the Black-naped Tern performs a variety of aerial acrobatics, including sweeping dives and chases with its mate. These displays are usually accompanied by vocalizations, which serve to strengthen the pair bond.

Self Maintenance

The Black-naped Tern exhibits regular maintenance behaviors, such as preening and bathing. Preening is important for the maintenance of its flight feathers, while bathing is used for cleaning and cooling off.

Agonistic Behavior

The Black-naped Tern exhibits agonistic behavior when defending its territory or young. This species is known to perform aerial displays and dive-bomb predators or other birds that invade its territory or come close to its chicks.

Sexual Behavior

The Black-naped Tern is a monogamous species, with pairs usually forming long-term bonds that last throughout the breeding season. Courtship displays usually involve the pair engaging in coordinated aerial displays and vocalizations, strengthening their pair bond.

Breeding

The breeding season of the Black-naped Tern varies depending on the location, with populations in the northern part of the range breeding from April to September and populations in the southern part of the range breeding from November to February. During the breeding season, the Black-naped Tern forms large colonies on small, sandy islands or man-made structures such as jetties.

The species nests in shallow scrapes on the ground, often under small shrubs or rocks. The female lays a clutch of 1-2 eggs, which she incubates for around 24 days.

Both parents take turns incubating the eggs and caring for the chicks once they hatch. The chicks are precocial, meaning that they are born with downy feathers and are mobile from birth.

They are fed by both parents, who regurgitate food for them. The chicks fledge after around 21-25 days and become independent from their parents shortly after.

Demography and Populations

The Black-naped Tern is considered a species of Least Concern by the IUCN Red List, with a global population estimated between 1 and 5 million individuals. However, some populations have declined due to habitat loss, pollution, and hunting.

Some populations in the Maldives and Mauritius have even been considered extinct due to habitat destruction and hunting. Conservation efforts have been put in place to protect the Black-naped Tern’s populations, including the creation of protected areas and monitoring of breeding sites.

These efforts have resulted in some populations recovering in certain areas, but ongoing threats such as habitat loss and pollution continue to pose challenges for the species’ survival.

Conclusion

In conclusion, the Black-naped Tern exhibits a range of interesting behaviors, including aerial locomotion, self-maintenance, agonistic behavior, and courtship displays during the breeding season. The species nests in large colonies on small, sandy islands or man-made structures and raises precocial chicks that become independent after around 21-25 days.

While the Black-naped Tern is considered a species of Least Concern, ongoing threats such as habitat loss and pollution continue to pose challenges for its survival. Conservation efforts are vital for protecting the species’ populations and ensuring its long-term survival in the wild.

In conclusion, the Black-naped Tern is a fascinating species with unique characteristics that capture the imagination of bird watchers and enthusiasts alike. From its striking plumage and graceful flight to its diverse diet and complex behaviors, the Black-naped Tern is a species that is worthy of study and conservation.

Understanding the species’ systematics, history, movements, habitat, and behavior provides crucial insights into the challenges it faces, as well as the opportunities for its protection and conservation. By taking action to protect this species, we can ensure that future generations can continue to appreciate the beauty and importance of the Black-naped Tern in our world.

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