Bird O'clock

Flight Secrets Nesting Marvels: The Wonders of Christmas Island Swiftlets

The Christmas Island Swiftlet is a small bird species belonging to the family Apodidae. It is endemic to Christmas Island and is known for its unique nesting behavior, which involves building nests out of dried saliva.

In this article, we will explore the identification, plumages, and molts of this fascinating bird species.


Field Identification

The Christmas Island Swiftlet is a small bird, measuring about 9 centimeters in length and weighing about 9 grams. It has a distinctive swallow-like shape, with long, pointed wings and a short, forked tail.

Its plumage is shiny black on top and lighter grayish-brown underneath. It has a small, curved beak, and its legs and feet are black.

Similar Species

The Christmas Island Swiftlet can be easily distinguished from other swiftlets by its shiny black plumage and shorter tail. It is often confused with the Glossy Swiftlet, which is larger in size and has a longer tail.

However, the two species can be distinguished by their calls, with the Christmas Island Swiftlet having a more high-pitched and rapid call.


The Christmas Island Swiftlet has a single plumage, which is shiny black on top and grayish-brown underneath. However, juveniles have a slightly duller plumage and may have a whitish throat.


The Christmas Island Swiftlet undergoes a complete molt once a year, typically during the breeding season. During this time, the bird will shed its old feathers and grow new ones to replace them.

Molting can take up to several weeks and can be an energetically costly process for the bird.


In conclusion, the Christmas Island Swiftlet is a small, unique bird species that is known for its distinctive nesting behavior and shiny black plumage. By understanding its identification, plumages, and molts, we can gain a greater appreciation for this fascinating bird species and the important role it plays in the ecosystem.

Systematics History

The Christmas Island Swiftlet, scientifically known as Collocalia natalis, was first described by British ornithologist Edward Newton in 1883. However, it was not until the early twentieth century that its taxonomic classification was established.

In 1916, American ornithologist James Chapin placed the species in the genus Collocalia, which is derived from the Latin word “collo” meaning glue and “calia” meaning house, referring to its unique nesting behavior.

Geographic Variation

The Christmas Island Swiftlet is endemic to Christmas Island in the Indian Ocean, which is located about 380 kilometers south of Java, Indonesia. As such, there is no geographic variation within the species.


There are no recognized subspecies of the Christmas Island Swiftlet.

Related Species

The Christmas Island Swiftlet is one of over 90 species of swiftlets in the family Apodidae. It is most closely related to the Glossy Swiftlet (Collocalia esculenta), which is found in Southeast Asia and Australia.

The two species were once considered conspecific, but genetic analysis and vocalizations have since confirmed their distinct status.

Historical Changes to Distribution

The distribution of the Christmas Island Swiftlet has undergone significant changes throughout its history. The bird was originally found throughout Christmas Island, but the rapid deforestation and habitat destruction caused by the island’s phosphate mining industry in the early twentieth century greatly reduced its population.

As a result, the Christmas Island Swiftlet was eventually limited to the remaining forested areas of the island, particularly in the central plateau. However, the construction of housing and other infrastructure in these areas has further reduced the species’ habitat.

Today, the Christmas Island Swiftlet is considered to be vulnerable to extinction due to the ongoing threats of habitat loss and degradation. To address this issue, the Christmas Island National Park was established in 1980, with the aim of protecting the remaining forested areas on the island.

Efforts have also been made to reintroduce the bird to other parts of the island where suitable habitat exists, such as in the northern and eastern coastal regions. In conclusion, the Christmas Island Swiftlet’s taxonomic classification, geographic variation, subspecies, and related species have been established through the work of ornithologists over time.

However, the bird’s current status as a vulnerable species highlights the importance of conservation efforts and the need to protect its habitat in order to ensure its survival for future generations.


The Christmas Island Swiftlet is restricted to the island of Christmas Island, where it is found in mature rainforest, secondary growth, and coconut plantations. It favors areas with tall trees, as well as caves and other cavities for nesting.

The bird is an especially skilled flier, known to fly high above the treetops during the day and then return to its nest at night. It forages exclusively over the dense rainforest, where it feeds on flying insects that it catches in mid-air.

The swiftlet’s strong wings and aerial agility make it a skilled hunter and able to evade predators.

Movements and Migration

As an endemic species, the Christmas Island Swiftlet does not migrate to other areas. It is a resident bird, meaning that it remains on the island throughout the year.

However, the bird has been known to move to different areas of the island in response to changes in food availability or habitat. During periods of drought, for example, the swiftlet may move to areas where there is more water, such as near the coast, in search of food.

Despite its limited movements, the Christmas Island Swiftlet plays an important ecological role by pollinating the island’s vegetation. As the bird moves from tree to tree in search of food, it transfers pollen from one flower to another, aiding in the reproduction of plant species on the island.

Threats to

Habitat and Migration

The Christmas Island Swiftlet is listed as a vulnerable species due to habitat loss and degradation caused by human activities. Deforestation, land clearing, and residential development have considerably reduced the bird’s habitat on the island.

Moreover, introduced predators, such as feral cats, rats, and snakes, pose a significant threat, as they prey upon the swiftlet’s nestlings. The bird’s reproductive success is further threatened by the harvesting of its nests for human consumption, a practice that has been rampant in some Asian countries.

These nests, made of the bird’s saliva, are harvested and processed for use in bird’s nest soup, a delicacy among some cultures. Due to the high demand, poachers have been known to climb into caves to extract the nests, risking injury to the birds and damage to their habitat.

Conservation Efforts

To address the threats to the Christmas Island Swiftlet’s habitat, a number of conservation efforts have been instituted. The Christmas Island National Park, established in 1980, has played a significant role in protecting the bird’s remaining habitat on the island.

The park’s management plan includes measures to control invasive species, restore degraded habitat, and limit new development. Another conservation initiative is the Christmas Island Swiftlet project, which aims to monitor the bird’s population and movements, provide information on its habitat requirements, and develop strategies for its conservation.

The project also conducts public education and outreach to raise awareness about the importance of the bird and its habitat. In addition, the Christmas Island Tourism Association has implemented best practices for sustainable tourism, promoting low-impact activities and responsible nature-based tourism that minimizes the impact on the swiftlet’s habitat.

In conclusion, the Christmas Island Swiftlet’s habitat requirements and limited movements have made it vulnerable to habitat loss and degradation caused by human activities. To ensure the survival of this important species, there is a need for effective conservation measures that address the threats to its habitat and promote sustainable practices to minimize human impact.

Diet and Foraging


The Christmas Island Swiftlet is an insectivore, feeding on a variety of flying insects such as flies, moths, and mosquitoes. The bird feeds exclusively in flight, making use of its highly efficient and maneuverable wings.

The swiftlet is known for its aerial agility and speed, capable of catching flying insects mid-air with ease. The bird feeds throughout the day, pausing only for short periods of rest in between.


The Christmas Island Swiftlet’s diet varies depending on the time of year and the availability of food. Insects found in the forest canopy, such as termites and ants, are more abundant during the wet season, while insects that inhabit the undergrowth, like spiders and beetles, are more common during the dry season.

The swiftlet is also known to feed on the fruits and nectar of certain plant species, sometimes dipping its bill into flowers to drink the nectar.

Metabolism and Temperature Regulation

The metabolism of the Christmas Island Swiftlet is highly adapted to its aerial foraging behavior. The bird’s respiratory system, in particular, is highly efficient, allowing it to process large amounts of oxygen needed for sustained flight.

Additionally, the swiftlet has a high body temperature, which helps maintain its body functions during flight. To regulate its body temperature, the Christmas Island Swiftlet uses a technique called panting, which involves rapid opening and closing of the beak.

This rapid movement helps circulate air through the bird’s respiratory system, facilitating heat exchange and helping to dissipate excess heat.

Sounds and Vocal Behavior


The Christmas Island Swiftlet is known for its high-pitched, rapid vocalizations, which are an important part of the bird’s social behavior. Male swiftlets use vocalizations to attract mates and establish their territory, while female swiftlets use vocalizations to communicate with their mates and offspring.

The bird’s vocalizations consist of a series of high-pitched, rapid notes, typically lasting about 0.2 to 0.5 seconds. These vocalizations are often given in flight, as the bird swoops and dives in aerial displays.

The swiftlet’s vocalizations have a distinctive chirping quality, which is often described as sounding like a “squeaky toy.”

Interestingly, the Christmas Island Swiftlet’s vocalizations have been observed to change with the seasons. During the breeding season, for example, males will give more complex vocalizations, which may include trills, buzzes, and other variations.

This change is thought to reflect the bird’s reproductive condition and may help to attract a mate.


In conclusion, the Christmas Island Swiftlet’s diet and foraging behavior are closely linked to its highly efficient respiratory system, which allows the bird to process large amounts of oxygen needed for sustained flight and aerial foraging. The bird’s vocalizations, meanwhile, play an important role in its social behavior, reflecting its reproductive condition and helping to establish territory and attract mates.

The swiftlet’s unique adaptations and behaviors make it a fascinating species to study, highlighting the intricate relationships between bird physiology, behavior, and ecology.



The Christmas Island Swiftlet is known for its highly efficient and maneuverable flight, which allows it to forage for insects in the air. The swiftlet is also capable of rapid turns and dives, making it a skilled hunter and evading predators.

The bird’s wings are narrow and pointed, providing excellent lift and efficiency during flight, while their short, forked tails help with agility in the air.


The Christmas Island Swiftlet is a clean bird and takes care to preen its feathers regularly, ensuring the proper functioning of its wings and maintaining its health. The bird also engages in wing stretching, which helps to strengthen the powerful muscles needed for sustained flight.

Additionally, the swiftlet uses saliva from its salivary glands to construct and maintain its nests, which are essential for reproduction.

Agonistic Behavior

During the breeding season, male Christmas Island Swiftlets engage in agonistic behavior to establish their territories and attract mates. This behavior can include aerial displays, vocalizations, and physical aggression towards other males that encroach on their territory.

However, unlike some other bird species, this behavior rarely leads to physical contact or injuries, as the swiftlets usually use vocalizations and displays to establish dominance.

Sexual Behavior

Christmas Island Swiftlets are monogamous and form pair bonds that can last for the duration of their lifespan. During courtship, male birds will engage in high-speed flights and aerial displays, accompanied by rapid vocalizations, to attract their potential mate.

They will also offer nesting material, such as plant matter, to the female as part of their courtship behavior.


The breeding season of the Christmas Island Swiftlet occurs between August and February, coinciding with the rainy season on the island. During this time, swiftlets construct their unique nests out of dried saliva and other materials attached to the ceilings of caves, or in crevices in cliffs.

The nests are small, cup-shaped structures, and are often constructed in large colonies. Once the nest is complete, the female will lay a single egg, which both parents will take turns incubating for about 20 days.

After hatching, the parents will continue to share the duties of feeding and caring for the chick until it is ready to leave the nest, usually after about 35 days. Nestlings are vulnerable to predation by introduced predators such as rats and cats, putting them at risk of extinction.

Demography and Populations

The Christmas Island Swiftlet is listed as a vulnerable species by the International Union for Conservation of Nature (IUCN) due to its small and declining population.

Habitat loss and fragmentation, coupled with the introduction of predators, have significantly reduced the swiftlet’s numbers on the island.

Conservation efforts are underway to protect the remaining population of Christmas Island Swiftlets. This includes habitat restoration programs, predator control measures, and the development of nesting boxes to encourage nesting outside of caves, which are more vulnerable to predation.

Scientific monitoring and research, such as the Christmas Island Swiftlet project, are also contributing to our understanding of the species and helping to coordinate conservation efforts. In conclusion, the Christmas Island Swiftlet’s behavior is closely tied to their unique adaptations for flight and aerial foraging.

Their nesting behavior, courtship displays, and parental care all underscore the importance of their unique ecology in mating rituals, breeding, and population maintenance. Efforts to conserve this species must take into account their close relationship with the island’s environment, and focus on habitat preservation and management to ensure the longevity of this species.

The Christmas Island Swiftlet is a small bird species that is endemic to Christmas Island, located in the Indian Ocean. Despite being vulnerable to extinction, the bird’s unique adaptations and behaviors make it an important species for ecological research.

Through our understanding of this species, we learn about the intricate relationships between bird physiology, behavior, and ecology, and the importance of conservation efforts to protect vulnerable species. The swiftlet’s habitat requirements, diet and foraging behavior, vocalizations, and breeding behaviors are just some of the topics that help to illustrate their importance and highlight the need for additional research and conservation initiatives.

Through a continued commitment to protecting this unique species, we can help ensure a brighter future for both the Christmas Island Swiftlet and other ecologically significant bird species around the world.

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