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Discover the Fascinating Life of the Aerobatic Blyth’s Swift

Bird: Blyth’s Swift, Apus leuconyxThe Blyth’s Swift, also known as Apus leuconyx, is a small bird of the swift family, which is found in parts of tropical and subtropical Asia. These swifts are often spotted flying high in the sky at great speeds, making sharp turns and darting after insects.

In this article, we will learn more about the identification, plumage and molts of the Blyth’s Swift.



Identification: The Blyth’s Swift is a small bird, measuring about 14 cm in length. It has a dark brownish-gray body, with a paler throat and underparts.

It has long, narrow wings and a short, forked tail. Its bill is small and black, and the eyes are dark.

Similar Species: The Blyth’s Swift looks quite similar to the Little Swift and the Pacific Swift, but can be distinguished by its paler throat and underparts.


The Blyth’s Swift has only one plumage, which is the adult plumage. The sexes are similar in appearance, although the male may have slightly longer wings than the female.


The Blyth’s Swift undergoes a complete molt every year, during which it sheds all its feathers and grows a new set. The molt usually takes place after the breeding season, and may last for several weeks.

During the molt, the bird may become less active and spend more time preening its feathers. In conclusion, the Blyth’s Swift is a fascinating bird that can be easily identified by its small size, narrow wings, and dark brownish-gray body.

While it does not have any unique plumages or molts, it is still a joy to watch these swifts fly through the sky with such grace and speed.

Systematics History

The Blyth’s Swift, Apus leuconyx, belongs to the family Apodidae, which comprises over 90 species of swifts found throughout the world. The classification of the Apus genus has undergone numerous changes over the years due to advancements in genetics and molecular biology.

The Blyth’s Swift was first described by George Robert Gray in 1845, based on a specimen collected from the island of Java. Since then, its systematics have been continuously studied, leading to important discoveries about its geographic variation, subspecies, and related species.

Geographic Variation

The Blyth’s Swift has a wide geographic distribution, ranging from the Indian subcontinent to Southeast Asia, China, and Taiwan. Its range overlaps with several other species of swifts, which can sometimes make identification challenging.

However, there are some physical and vocal differences that can help distinguish the Blyth’s Swift from other species.


There are two recognized subspecies of the Blyth’s Swift, Apus leuconyx leuconyx and Apus leuconyx saturatus. The nominate subspecies, A.

l. leuconyx, is distributed throughout most of the species’ range, while A.

l. saturatus is found in northeastern India and Nepal.

The subspecies differ slightly in their plumage, with A. l.

saturatus having a slightly darker throat than A. l.


Related Species

The Blyth’s Swift is closely related to other species of swifts within the Apus genus, including the Pacific Swift and the Little Swift. The Pacific Swift, Apus pacificus, is found throughout much of Asia, Australia, and the Pacific islands, and is similar in appearance to the Blyth’s Swift, but has a darker underbelly.

The Little Swift, Apus affinis, is found in sub-Saharan Africa and southern Asia and is smaller than the Blyth’s Swift, with a less forked tail.

Historical Changes to Distribution

The Blyth’s Swift has undergone some changes in its range over time, affected by both natural and human factors. In the late 1800s, the species was recorded from Thailand, but was not seen in the country again until the 1980s.

This decrease in sightings may be attributed to habitat destruction and hunting by humans. The species has also become more widespread in recent years, with sightings reported as far north as Japan and South Korea.

This expansion of the range may be due to changing climate patterns or adaptations to urban environments. In conclusion, the systematics of the Blyth’s Swift have been continuously studied and refined over the years, leading to a better understanding of its geographic variation, subspecies, and related species.

It is one of several species of swifts found throughout Asia, and its range has undergone some changes over time due to natural and human factors. Despite these changes, the Blyth’s Swift continues to be a widespread and fascinating bird, known for its speedy flights and unique vocalizations.


The Blyth’s Swift is primarily a bird of open habitats such as grasslands, savannas, and scrublands. It also occurs in agricultural lands, urban areas, and forest edges.

The species is found across a wide elevation range, from sea level up to around 2,500 meters in the Himalayas. It is often observed flying high in the sky, catching insects on the wing.

The species is more commonly seen during the breeding season, as it remains high in the air, making it challenging to spot. However, during the non-breeding season, the Blyth’s Swift may roost in groups in sheltered locations such as cavities in trees or buildings.

Movements and Migration

The Blyth’s Swift is a long-distance migrant, and its movements vary depending on the season. In the breeding season, the species is found across much of South and Southeast Asia, from India and Pakistan to southern China and Southeast Asia.

During this time, it is thought that the species may be a partial migrant, with some birds remaining in the breeding range year-round. Others may move to higher elevations to breed during the summer months.

There is limited information on the breeding behavior of the Blyth’s Swift, but it is known to breed in small colonies, with pairs at a distance from each other. In the non-breeding season, the Blyth’s Swift migrates to Southeast Asia, where it is thought to overwinter across a broad range extending from the eastern Himalayas to the Philippines, Borneo, and northern Australia.

It is believed that the species undertakes a clockwise migration, moving from the breeding grounds in India and Southeast Asia to the non-breeding grounds in Indonesia and Australia. In some regions, such as the Philippines, the Blyth’s Swift appears to be a common migrant, with large numbers passing through during migration periods.

The Blyth’s Swift is known to be highly aerial, meaning that it spends most of its time in flight, traveling long distances in search of food. It is also thought that the species may sleep on the wing, which allows it to conserve energy during long journeys.

Recent tracking studies have shown that the Blyth’s Swift is capable of impressive feats of endurance, covering vast distances without rest. In one study, a Blyth’s Swift was tracked flying for over 10,000 kilometers across the Indian Ocean, which is one of the longest flights ever recorded for a bird of its size.

In conclusion, the Blyth’s Swift is a fascinating bird with highly aerial behavior. It is an open habitat species, found in a variety of habitats throughout its range.

The species breeds across much of South and Southeast Asia and migrates to Southeast Asia and parts of Australia during the non-breeding season. Recent tracking studies have revealed impressive endurance capabilities of the species, underscoring one of its most remarkable traits.

Diet and Foraging

The Blyth’s Swift is an insectivorous species that feeds almost entirely while in flight. It is known for its remarkable aerial agility, which allows it to catch insects, including flies, wasps, and dragonflies, on the wing.

The swift captures its prey with its bill and then transfers it to its gullet while still in flight. Because the swift spends most of its time in the air, it requires a high intake of food relative to its body size.


The Blyth’s Swift eats a wide range of insect prey. As an aerial insectivore, it is limited to prey that is available in the air, such as insects that are flying or hovering.

Its feeding style limits it to relatively small, agile, and often elusive insects, and the swift has adapted to this by becoming a highly skilled flyer and hunter in the air. Unlike many other birds, the Blyth’s Swift does not drink water in a conventional way but rather obtains water while in the air.

While foraging for insects, the swift may also intercept falling raindrops or fly through mist to obtain moisture. This technique allows it to stay hydrated while not landing.


The specific diet of the Blyth’s Swift varies depending on the location and seasonal availability of insects. It is thought that the species may feed on different types of insects depending on the time of year, with certain species being more abundant at certain times.

Blyth’s Swifts in the Himalayas have been observed feeding on a range of insects, including termites, beetles, and flies. Meanwhile, those in Southeast Asia feed on insects such as gnats and blackflies.

The high metabolic rate of these swifts means that they have to obtain high levels of protein, especially during the breeding season, to support reproductive processes.

Metabolism and Temperature Regulation

The Blyth’s Swift has a high metabolic rate and must consume a large amount of food to sustain energy expenditure. The species has developed several adaptations that allow it to regulate its temperature more effectively while in flight.

For example, it has a relatively small body mass, which reduces heat loss. Additionally, the feathers on its body are tightly and closely packed, minimizing the area for heat loss.

Because the swift spends most of its time flying, it is also exposed to colder temperatures at night, which is why its ability to maintain body heat is so important.

Sounds and Vocal Behavior

The vocalizations of the Blyth’s Swift are an important aspect of its communication. These birds have a range of calls and songs that are used for a variety of purposes, including navigation, social interaction, and courtship.

The vocalizations of the Blyth’s Swift are typically described as high-pitched, harsh, and rasping.


The Blyth’s Swift has few vocalizations, with its repertoire consisting mostly of short, high-pitched, and buzzy calls. These calls are used to identify conspecifics and may be used in navigation during migration.

The calls are typically delivered when the bird is in flight and are often repeated in rapid succession. The species may also make a variety of vocalizations that are used for different purposes, including courtship displays and territorial defense.

One of the most commonly heard vocalizations is a buzz, which is typically heard when a group of swifts is flying together. This sound is produced by the wings of the swifts as they move rapidly through the air, creating a distinctive buzzing sound that is instantly recognizable.

In conclusion, the Blyth’s Swift is a fascinating species with unique adaptations that make it highly adapted to its aerial lifestyle. Its diet consists almost entirely of insects, which it catches while in flight, and its metabolic rate is extremely high, which requires high energy expenditure.

The species has developed many adaptations, including minimizing body mass and tightly-packed feathers, to regulate its body temperature.

Vocalizations also serve as an important mode of communication for the Blyth’s Swift, including calls and songs used for navigation, social interaction, and courtship.



The Blyth’s Swift is a highly aerial species that is exclusively adapted to flying and spends most of its life in the air, making it an efficient flyer. It can reach speeds of up to 100 kilometers per hour and can fly continuously for extended periods of time, with one bird being recorded flying continuously for over 10,000 kilometers.

The swift has a unique, aerodynamic shape that allows it to be exceptionally maneuverable in the air, making it an agile hunter that can catch flying insects with ease. When it does land, it is either to roost or to mate.

Self Maintenance

The Blyth’s Swift is known to be a fastidious preener, keeping its feathers in excellent condition. Its feathers are designed to be tight against its body, facilitating flight and protecting the bird from temperature changes and humidity.

This tight feathering requires regular preening to prevent damage and keep it clean, which the bird does by running its beak along the length of them while clapping its wings together repeatedly.

Agonistic Behavior

The Blyth’s Swift is a social species that forms groups during migration and outside of the breeding season. However, during the breeding season, the swift can also display agonistic behavior.

Males may defend their territory from rival males, and conflicts between birds may break out. Fighting may involve pecking, biting, and grappling or wrestling.

Flapping and striking with the wings may also occur.

Sexual Behavior

The Blyth’s Swift is typically monogamous during the breeding season, with males vying for the attention of females through courtship displays. The males engage in aerial displays, including short chases and circles around the female, where they may display their agility and call to one another.

The male will then land, bowing and raising his wings to nearby females. When the female is receptive, the pair will mate.


Little is known about the breeding of the Blyth’s Swift. The birds nest in small colonies under the eaves of buildings or in other sheltered locations.

The nests are made of a variety of materials, including feathers, insect wings, and grass. The species is believed to be monogamous, with pairs forming during the breeding season.

The female lays a single egg, which is incubated for approximately 21 to 24 days. The chick is fed by both parents, with each member of the pair catching insects and transferring them to the chick while in flight.

After around 45 days, the chick leaves the nest and begins to fly. The pair may also raise a second brood in the same season.

Demography and Populations

The Blyth’s Swift is a widespread species with a large population size. Its global population has not been quantified, but its distribution across much of South and Southeast Asia suggests that its numbers are large.

The species is also not considered to be globally threatened, with a population that appears to be stable and is not experiencing significant declines. However, there may be local populations that are declining due to habitat loss and hunting, and the species may be sensitive to environmental changes.

Nonetheless, the Blyth’s Swift continues to be a fascinating bird that serves as a valuable example of an avian species that is highly adapted to its aerial lifestyle. Overall, the Blyth’s Swift is a unique and remarkable bird species.

It has evolved numerous adaptations that allow it to effectively hunt insects while in flight and regulate its body temperature. Its highly aerial lifestyle also impacts its behavior, including locomotion, self-maintenance, and social interactions.

While we still have much to learn about the ecology and behavior of the Blyth’s Swift, continued study of this species is essential to understanding the broader effects of climate change and habitat loss on aerial insectivores around the world. The Blyth’s Swift serves as a critical reminder of the interconnectedness of all living organisms and the importance of protecting our planet’s rich biodiversity.

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