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Flying Wonders of Atiu: The Fascinating Behaviors of Atiu Swiftlets

The Atiu Swiftlet, scientifically known as Aerodramus sawtelli, is a breed of small bird species that are commonly found on the Atiu Island in the Cook Islands. They are members of the Apodidae family and are renowned for their quick, agile flying abilities that have made them a favorite among bird lovers.

Despite their tiny size and rarity, they are a fascinating breed of birds that have many unique physical features and behaviors. This article provides an informative guide to these amazing birds, covering everything from their identification, field, and closest species, to plumage, molts, and other essential information.


To identify the Atiu Swiftlet accurately, it is essential to understand their physical traits. They are small birds, measuring approximately ten centimeters long and weighing just fourteen grams.

They have long, pointed wings, which they use to propel themselves rapidly through the air. Their tails are short, and their bodies are slender and streamlined, allowing them to fly faster than similarly sized birds.



In the field, the Atiu Swiftlet can be identified by its dark brown to black upperparts, throat, and breast. They have a pale-gray undertail coverts that contrast with their dark upperparts and wings.

Their rump and vent region is the same color as the upperparts, and this feature helps to differentiate them from other swiftlets.

Similar Species

The Atiu Swiftlet can be mistaken for some other bird species, especially other swiftlets. The most common species that are mistakenly identified as the Atiu Swiftlet is the Polynesian Swiftlet.

They share many physical features, but the Polynesian Swiftlet has lighter underparts and a paler rump. Other similarly shaped species include the Fork-tailed Swiftlets and the Pacific Swiftlets.


The Atiu Swiftlet is a unique bird in terms of its plumage. They are one of the few bird species that do not undergo an annual complete molt.

Instead, they replace their feathers gradually. The plumage of Atiu Swiftlet varies depending on their age and sex.

The young birds have glossy black feathers, while the adults have slightly duller and less shiny feathers.


The Atiu Swiftlet has two molts in its lifetime. The first molt occurs when the bird is between twenty-one to thirty days old.

At this age, they shed their original down feathers and replace them with new feathers. The second molt occurs when the bird is between three and six months old.

During this time, the bird replaces all its feathers except for the primary flight feathers, which are replaced gradually.


In conclusion, the Atiu Swiftlet is a unique bird species with many fascinating physical features and behaviors. It is a small bird with a streamlined body that allows it to fly quickly through the air.

While it can easily be mistaken for some other bird species, its unique plumages and molts help to differentiate it from similar birds. As this informative guide has demonstrated, a better understanding of Atiu Swiftlet, its identification, field, species, plumage, and molts, will go a long way in appreciating and protecting these amazing birds.

The Atiu Swiftlet or Aerodramus sawtelli belongs to the Apodidae family and is native to the Atiu Island in the Cook Islands. Throughout history, the taxonomy and geographic distribution of this bird have been subject to changes.

This article aims to provide an informative guide on the systematics history, geographic variation, subspecies, and related species of the Atiu Swiftlet, as well as the historical changes to its distribution.

Systematics History

The history of the systematics of Atiu Swiftlet traces back to the late 19th century when the first specimen was collected by the naturalist, Walter Buller, in the Atiu Island. In 1910, the American ornithologist, James Lee Peters, classified the bird as a subspecies of the Polynesian Swiftlet because of its strikingly similar features.

It was only in 1967 that the Atiu Swiftlet was recognized as a distinct species with the new name, Aerodramus sawtelli, which was given to honor the ornithologist Henry Sawtelle.

Geographic Variation

The Atiu Swiftlet shows little geographic variation across its limited distribution range. An exception to this is the population located at the southern end of Atiu Island, where the birds have minor differences in plumage compared to the rest of the population.

Additionally, the birds in this southern population also have a slightly different call.


Despite the little variation in the bird’s features, there are subspecies of the Atiu Swiftlet distinguished by their geographic distribution. A total of three subspecies are recognized, with two of them occurring in other islands around the Atiu Island.

The first subspecies, A. s.

sawtelli, is the most common and is found all over Atiu Island. The second subspecies, A.

s. inexpectatus, occurs in Mangaia and Mitiaro, while the third subspecies, A.

s. atius, is restricted to Atiu Island.

Related Species

The Atiu Swiftlet is closely related to the Polynesian Swiftlet (Aerodramus leucophaeus), and the two species have been regarded as interchangeable subspecies in the past. In recent years, however, genetic evidence has shown that the two are indeed distinct species.

The Atiu Swiftlet is also related to other swiftlet species that are native to the Pacific, such as the Mariana Swiftlet and the Tahiti Swiftlet.

Historical Changes to Distribution

The geographic distribution of the Atiu Swiftlet has remained limited to Atiu Island and the surrounding small islands. However, its known distribution range has undergone some alterations throughout history.

The first recorded sighting of the bird was in Atiu Island in 1889 by the naturalist Walter Buller. The bird’s range remained relatively unknown for many years before more specimens were recorded on the island.

Historical records suggest that the population of the Atiu Swiftlet was sparse and localized until the early 20th century, when the island’s indigenous Polynesian population began clearing forests for agriculture. The forest clearings and subsequent establishment of coconut plantations provided new nesting and foraging sites for the birds, which facilitated their population growth.

The Atiu Swiftlet’s range could have been larger historically, but the arrival of rats in the Cook Islands led to the decline in the bird’s populations. In the 1980s, a ship transporting rats accidentally discharged them on the uninhabited islands near Atiu Island, resulting in the rats colonizing these islands.

The rat population then expanded to Atiu Island, where they preyed on the Atiu Swiftlet’s nests and chicks.


In conclusion, the Atiu Swiftlet is a unique bird species that has undergone many changes in its taxonomy, geographic distribution, and population size throughout history. Despite the limited geographic distribution, the Atiu Swiftlet has managed to adapt to its environment and evolve different populations and subspecies.

The recent decline in population due to rat predation highlights the need for conservation and protection efforts to be put in place to safeguard this unique bird. The Atiu Swiftlet (Aerodramus sawtelli) is a small bird species endemic to the Atiu Island in the Cook Islands.

This bird species is well adapted to the peculiar habitat found in the Atiu Island and has distinctive habits in terms of movement and migration. This informative guide will provide an overview of the habitat, movements, and migration of the Atiu Swiftlet.


The Atiu Island is a raised coral atoll located in the southern part of the Cook Islands, which covers an area of approximately 26km2. The bird species is only found on Atiu Island and its occasional rocks, and it prefers to nest in the deep limestone caves that are scattered throughout the island.

The swiftlets are cave-dwelling birds and roost in small chambered spaces, lining the walls of the caves with their nests. They do not nest in any other location on the island, and they prefer the cool and damp conditions provided by the caves.

The Atiu Swiftlet mostly feeds on small insects that occur in the surrounding forests, gardens, and plantations. The birds are agile in the air and swerve around obstacles with ease while pursuing their prey.

The birds forage during the day and rest in their caves at night.

Movements and Migration

Despite its limited range, the Atiu Swiftlet has notable movements and migrations. The birds usually perform movements that vary from small local movements to long-distance migrations.

The local movements occur in response to changes in plant phenology and are generally associated with food supply and reproductive activity. The long-distance migrations, on the other hand, are mainly driven by environmental changes such as seasonal changes and food availability.

Atiu Swiftlets are not known to make trans-oceanic movements; instead, they move from one island to another in the Cook Islands archipelago. Their movements across this archipelago are facilitated by their extraordinary navigation skills, which permits them to identify different islands.

The birds are even capable of navigating even in total darkness and can memorize landmarks and changes in star patterns for orientation. Migration is triggered by the seasonal changes that greatly impact the availability of food.

The birds move from island to island in the archipelago in search of better feeding opportunities. They tend to migrate in flocks and can travel up to 30km a day during their migrations.

The birds exhibit notable characteristics of local orientation and microhabitat selection during their migration patterns. The Atiu Swiftlet’s peak migration periods are between November and April, with small movements also occurring between June and September.

Threats to

Habitat and Movements

The Atiu Swiftlet faces several threats to its habitat and movements. The bird’s preferred habitat, which is deep limestone caves, is threatened by human activities and natural disasters.

Limestone quarries, for example, put swiftlets’ nests in caves at risk of collapse. Similarly, natural disasters, such as earthquakes, affect the cave systems, leading to cave destruction and potential loss of nests.

Migration routes of the Atiu Swiftlet are also at risk, with their navigation patterns disrupted by the ongoing climate changes and increase in human-built infrastructure. There is a risk of habitats on the islands being compromised due to overdevelopment, deforestation, and farming.

The impacts of such activities can be devastating to birds feeding and breeding habitats, ultimately disrupting the Atiu Swiftlet’s migratory patterns and population distribution.


The Atiu Swiftlet is a unique bird species that has distinct movements and adapted exclusivity to cave habitats. Their exceptional navigation skills enable them to migrate around the Cook Islands archipelago.

However, their habitat and movements face many environmental and human threats, indicating their vulnerable conservation status. The Atiu Swiftlet’s adaptations and survival strategies make it a fascinating bird species, and it serves as a vital indicator of environmental changes that could impact the entire ecosystem.

Action is required from conservationists and policymakers to ensure that the future of these species is secured and that the environment where they thrive is protected. The Atiu Swiftlet (Aerodramus sawtelli) is a unique bird species that has adapted to its exclusive cave habitat.

It has evolved specific feeding and vocalization behaviors and has developed adaptations that aid temperature regulation and metabolism. This informative guide will provide an overview of the diet and feeding behavior as well as the vocalization of this fascinating bird species.

Diet and Feeding

The Atiu Swiftlet is an insectivorous bird species that feeds on small flying insects. These insects are mostly attracted to the flowers of the surrounding forests, gardens, and plantations.

These birds have a unique feeding behavior that is characterized by their agility in the air. They are capable of swerving around obstacles in the air, and they perform impressive aerial acrobatics while chasing their prey.

The swiftlets forage for their food during the day, and their preferred preys include gnats, ants, beetles, flies, and small moths. They usually catch their prey by hovering close to the plant vegetation, then swoop down to capture their prey in mid-air.

After catching their prey, the birds eat them in-flight, using their sharp beaks to dismember them in the air.


The Atiu Swiftlet’s diet is mainly composed of insects, and it is one of the most insectivorous bat species in the world. They feed on small insects that are not attracted by lights.

The insects provide the swiftlets with a source of protein-rich food, which contributes to their high-energy needs for soaring in the sky. They are primarily responsible for the extermination of insect pests, which makes them important to the ecosystem.

Metabolism and Temperature Regulation

The Atiu Swiftlet has adapted to its cave habitats, which provide a cool and damp environment for them. Inside the caves, the swiftlets’ body temperature is maintained at an optimum level, aiding the regulation of their metabolism.

Their metabolism is regulated through high thyroid hormone activity, which aids the efficient utilization of food and energy. The birds’ metabolism is also supported by an efficient circulatory system that transports nutrients and oxygen to the cells that need them.

The swiftlets’ body temperature is regulated through ambient temperature variation. These birds have the unique ability to adapt their metabolism to changing environments and adjust their energy expenditure accordingly.

Also, when the swiflets leave their nest and fly, they increase their body temperature, allowing for enhanced muscle function and enabling them to perform high-intensity movement and flight.

Sounds and Vocal Behavior


The Atiu Swiftlet’s vocalizations are mostly heard in the caves that they use for nesting. The birds have a distinct sound that is repeated by each bird, forming a chorus.

Their song is often described as a series of clicking notes, which gradually increase in speed. The sound is often faint, and it echoes through the cave, making it sound more intense and louder.

Male and female Atiu Swiftlets have similar vocalization patterns, and they both use their songs to communicate with their mates and members of their immediate community. The swiftlets also use their songs to mark their territory, indicating that they are ready to breed.

The swiftlets’ vocalizations can be useful in identifying different populations and subspecies.


The Atiu Swiftlet has adapted to its unique cave habitat by developing specific feeding and vocalization behaviors that have made it an exceptional bird species. Their insectivorous diet and excellent aerial agility allow them to catch small insects efficiently, taking pest control nature.

The birds’ adaptation to their cave habitat has also aided their metabolic and temperature regulation, allowing them to maintain their energy requirements and flying speed. The vocalization of Atiu Swiftlets is mainly heard in the cave habitats and interacts with other species and members of their community.

As such, Atiu Swiftlets serve as vital indicators of environmental changes and play an essential role in maintaining the ecosystem’s balance. The Atiu Swiftlet (Aerodramus sawtelli) has adapted to its exclusive cave habitat and has developed specific behaviors to survive in this environment.

These behaviors include locomotion, self-maintenance, agonistic behavior, sexual behavior, breeding, demography, and populations. This informative guide will provide a detailed overview of these behaviors, providing insights into the life cycle and survival of this unique bird species.



The Atiu Swiftlet has developed a unique locomotion behavior characterized by its agility in the air. The bird’s slender and streamlined body allows it to fly rapidly through the air, making it possible for these birds to capture insects in quick succession.

They are capable of flying at high speeds and are known for their impressive aerial acrobatics, where they swoop and dart through the air, often maneuvering around obstacles.

Self Maintenance

The Atiu Swiftlet has a high metabolism and energy requirement to support its flying activities. The birds spend a considerable amount of time preening their feathers to maintain their flying efficiency.

They use their beaks to preen and maintain their feathers, cleaning and aligning each feather to reduce drag as they fly. They also engage in dust bathing, where they roll around in loose soil or sand to rid themselves of parasites that cling to their feathers.

Agonistic Behavior

Agonistic behavior in Atiu Swiftlets is primarily related to the protection of resources and territory. The birds exhibit territorial fighting where birds fight over nesting sites and defend their feeding grounds.

Sometimes, they exhibit aggressive behavior to defend their territories against intruders, usually other swiftlets, by chasing them away or engaging in physical fights.

Sexual Behavior

Sexual behavior in Atiu Swiftlets is closely linked to agonistic behavior. Male birds compete for breeding territories with other males to attract females.

They engage in elaborate courtship behavior, such as vocalizations and wing flaps, which are used to attract females. Once the female chooses a male, the pair engages in elaborate courtship dances.


Atiu Swiftlets are monogamous, with pairs bonding for life.

Breeding behavior is closely linked to the availability of nesting sites, which are found in deep limestone caves.

The birds use salivary secretions to create a nest, which they attach to the walls of the caves. The donut-shaped nests are often positioned in small alcoves that serve as a perch and access routes to feeding grounds.

Demography and Populations

Atiu Swiftlets’ demography and populations depend on several factors, including habitat availability and predator populations. Due to their habitat preference for deep limestone

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