Bird O'clock

Unlocking the Secrets of the Brush Cuckoo: From vocals to breeding behavior

The Brush Cuckoo, scientifically known as Cacomantis variolosus, is a bird species that is found in the tropical and subtropical regions of Asia and Australasia. Its distinctive call can often be heard in these areas, making it a recognizable bird species.

In this article, we will provide an introduction to the Brush Cuckoo bird species, discuss its identification, plumages, and molts.The Brush Cuckoo is a fascinating bird species that has captured the attention of many ornithologists around the world. With its unique vocalizations and distinct physical features, this bird species has become a sought-after sighting for birdwatchers.

Understanding the identification, plumages, and molts of this bird species can provide a more in-depth appreciation for its beauty and behavior in the wild.


Field Identification: When attempting to identify a Brush Cuckoo in the wild, it is important to focus on its overall size and shape. The Brush Cuckoo is a relatively small bird measuring around 20-27 cm in length.

It has a long, slightly curved, dark beak, and a long tail that is often held upright. The upperparts of the bird are brown with white spots, while the underparts are a creamy white.

The eye of the male bird is red, while the females eye is brown.

Similar Species: The Brush Cuckoo species is relatively similar in appearance to other cuckoo species, making it easy to misidentify.

However, the main difference between the Brush Cuckoo and other similar species is its size and shape. The Brush Cuckoo is much smaller than the Common Koel, another bird species found in the same area.

Additionally, the Brush Cuckoo’s distinctive markings and call make it easily identifiable.


Plumages describe the various stages of feather growth and the associated patterns and colours. The Brush Cuckoo species has two plumages; the breeding plumage and the non-breeding plumage.

The breeding plumage of males involves the bird having a black head and upperparts with white spots, white underparts with a brown ochre, or deep orange rufous, rectangular marking on the breast. The breeding plumage of females is similar, but they lack the rectangular marking found on the breast.

The non-breeding plumage, on the other hand, involves the disappearance of the black coloration resulting in a more uniform, lighter coloration for both males and females.


Molts are the process by which a bird sheds its old feathers and replaces them with new ones. A bird undergoes multiple molts throughout its life.

The Brush Cuckoo species experiences two molts; the pre-basic molt and the pre-alternate molt. The pre-basic molt is a process by which the bird sheds its old feathers and replaces them with new ones.

This molt occurs after the breeding season and before migration. On the other hand, the pre-alternate molt occurs when the bird receives new feathers in preparation for the breeding season.

The pre-alternate molt occurs in the southern hemisphere between April and June.


In conclusion, the Brush Cuckoo bird species is a unique and fascinating creature found in Asia and Australasia. Its distinctive call and physical features make it an intriguing subject for birdwatchers and ornithologists alike.

The identification, plumages, and molts of the Brush Cuckoo species offer insight into its behavior and biology. By understanding these factors, one can appreciate the beauty and significance of the Brush Cuckoo.

Systematics History

The Brush Cuckoo belongs to the Cuculidae family, which encompasses cuckoo species across the globe. Taxonomically, it has undergone several revisions, and its scientific name has changed over time.

Initially, it was named Cuculus variolosus, but it was later reclassified as Hierococcyx variolosus due to its morphology and vocalizations. Finally, molecular studies led to its current classification under the genus Cacomantis.

Geographic Variation

The Brush Cuckoo exhibits slight variations in plumage across its range, although these comprise gradual clinal variations rather than discrete geographic subspecies. Phenotypic differences have been observed in the tone of the back plumage, which ranges from dark brown to dark olive-brown in the northernmost part of the species range, and transforms into lighter brown in the south of its range.

Another noticeable variation is the extent of the white streaking on the crown, throat, and upper breast; this covert variation may be related to tracheal or syrinx anatomy, or the sounds produced during vocalizations.


Despite the clinal variation in Brush Cuckoo plumage, some sources recognize three subspecies of Cacomantis variolosus, namely C. v.

variolosus, C. v.

harterti, and C. v.

mirabilis. C.

v. variolosus is the most widespread subspecies of the Brush Cuckoo and breeds from the Himalayas to Thailand and the Malay Peninsula.

Its plumage is dark brown on its back and light brown underneath, with white spotting on its wings and tail. Its breeding season extends from March to September.

C. v.

harterti breeds in the Andaman Islands and may be distinguished from C. v.

variolosus by its darker plumage. C.

v. mirabilis is endemic to the Philippines and appears to be paler overall than the other two subspecies.

Related Species

The Brush Cuckoo is closely related to several other cuckoo species in its genus that have similar morphology and vocalizations. These include the Rufous-bellied Hawk-Cuckoo (Cacomantis sepulcralis), which has a range stretching from the Himalayas through Indochina to the Malay Peninsula, and the Rusty-breasted Cuckoo (C.

sepulcralis williamsoni), which is found in the Philippines. These species are visually similar to the Brush Cuckoo, although they exhibit differences in plumage and vocalizations.

Historical Changes to Distribution

The Brush Cuckoo species’ distribution has been altered due to human activities such as deforestation, wetland drainage, and rapid urbanization. Although the Brush Cuckoo remains relatively common throughout its range, it is declining due to habitat loss.

In areas where its habitat has been seriously degraded, the Brush Cuckoo has adapted to using secondary forests and even gardens and parks as alternative nesting or foraging sites. Island populations of the Brush Cuckoo, such as the subspecies C.

v. harterti in the Andaman Islands, have also seen significant declines due to the destruction of their forest habitats.

In some Pacific islands, such as Fiji and Samoa, the Brush Cuckoo has been introduced for insect control but has become naturalized and contributes to local ecosystems. Moreover, the global climate change may have an impact on specific range limits of geographic and climatic factors affecting the species’ viability.

Interpreting and forecasting the impact of such stressors remains an open area of research among ornithologists globally.


In conclusion, the Brush Cuckoo belongs to the Cuculidae family and has undergone several taxonomic revisions. Although the clinal variation in plumage does not translate into separate subspecies, three subspecies are still recognized by some sources.

The species, which is closely related to the Rufous-bellied Hawk-Cuckoo and Rusty-breasted Cuckoo, is relatively common throughout its range, but habitat loss remains a significant threat to its populations. Finally, certain demographic factors and climatic stressors may impact the Brush Cuckoo’s range and viability, warranting further research in the field.


The Brush Cuckoo prefers to inhabit primary and secondary lowland forests with an understory layer consisting of shrubs and bushes. The species is also found in mangroves, plantations, and the edges of forests.

Studies have shown that the presence of light gaps in forests can increase the abundance of Brush Cuckoos in an area. These gaps provide more space for shrubs and bushes to grow, which presumably increases the availability of food and nesting opportunities.

Brush Cuckoos consume a wide range of arthropods, including caterpillars, beetles, and grasshoppers. The availability of these insects varies between habitats and seasons, which explains the species’ preference for areas with a diverse range of vegetation and habitats.

Moreover, the Brush Cuckoo’s favored habitats in lowland tropical forests, which are dominated by fast-growing pioneer tree species and contain copious herbaceous plants, maintain a high level of insect diversity.

Movements and Migration

The Brush Cuckoo species is considered a short-distance migratory bird, moving between breeding and non-breeding sites within a region. Migratory movements are infrequent and differ between populations.

For example, populations breeding at higher latitudes tend to move southwards during the non-breeding season, while populations at lower latitudes remain resident in their breeding areas. During breeding season, the Brush Cuckoo is territorial and defends a small area that contains its nesting site and foraging grounds.

Despite their aggressive territoriality, Brush Cuckoos are known to exhibit a certain degree of tolerance regarding other birds’ proximity during the non-breeding season. This suggests that food resources and favorable habitats are key determinants of the species’ behavior outside of the breeding season.

Brush Cuckoos generally forage in the understory for insects, sometimes fly-catching from bare branches or perching in the open. Research suggests that this style of foraging within the understory may account for their preference for shrublands and drier forest margins.

Moreover, Brush Cuckoos undergo a pre-breeding migration from Northern Australia to Southern Australia before the breeding season. This migration pattern is also present in other Australian cuckoo species such as Shining Bronze-Cuckoo (Chrysococcyx lucidus).

Research using tracking devices has revealed that some Brush Cuckoos undertake movements associated with the weather patterns and resources availability. The Brush Cuckoo has a relatively short migration distance, typically moving up to 1,000 kilometers per year.

Northern populations have been observed moving into Southeast Asia during the non-breeding season while still staying within their region of origin. It is believed that these movements help the populations access more abundant food resources in areas with higher food availability.


In summary, the Brush Cuckoo species is found in a variety of habitats, preferring primary and secondary lowland tropical forests with an understory layer consisting of shrubs and bushes. Its foraging style within the understory layer may account for its preference for shrublands over taller forests.

Brush Cuckoos are territorial during the breeding season but exhibit tolerance outside of the breeding season, possibly due to food resource availability. The Brush Cuckoo is considered a short-distance migrant, moving between breeding and non-breeding sites within a region.

These movements typically occur during the pre- and post-breeding seasons and may be associated with weather patterns and food resource availability. Finally, ongoing ecological factors such as habitat loss, climatic stressors, and human activities continue to pose significant challenges for the survival of the species, highlighting the need for further conservation efforts by ornithologists and ecologists.

Diet and Foraging

Feeding: Brush Cuckoos feed primarily on insects. The species is known to forage in the understory of the forest, where it searches for insects to eat.

The Brush Cuckoo’s foraging style within the understory layer may account for its preference for shrublands over taller forests. The species commonly fly-catches, perches in the open or makes short flights to catch prey.

This species is also known to follow army ant swarms to prey on the insects that are flushed out by the ants. Diet: Brush Cuckoos consume a wide range of arthropods, including caterpillars, beetles, and grasshoppers.

The species is known to be opportunist, and it can adjust its diet based on the availability of prey items. Brush Cuckoos feed mainly on larvae or adults of moth and butterfly species, which provide the bulk of their diet.

Nonetheless, studies suggest that termites, and other insects may also make up an important part of their diet. During the breeding season, the Brush Cuckoo population in an area increases and consumes a more substantial amount of food, likely owing to the energetic demands of reproduction.

Metabolism and Temperature Regulation: The Brush Cuckoo’s metabolic rate and body temperature regulation are likely influenced more by external conditions than internal functions. Brush Cuckoos typically have relatively low metabolic rates, possibly due to their small size and the fact that the species does not fly for extended periods.

The species also has a low evaporative water loss, meaning they experience less water loss than other bird species.

Sounds and Vocal


Vocalization: The Brush Cuckoo has a distinctive and complex vocalization that comprises six distinct call types. The melodic and strikingly human-like characteristics of the song of the Brush Cuckoo have endeared the birdwatchers and naturalists alike.

The loud, fast, and double-noted whip-whip call of the Brush Cuckoo is often considered the species’ most distinctive vocalization, audible from far away. Different subspecies (if considered valid) are known to have slight variations in their call, making these vocalizations useful for sub-species differentiation.

Apart from its distinctive whip whistle, the Brush Cuckoo often vocalizes other sounds when threatened, such as a harsh trill or a fast chatter. The species’ vocalization is not only used as a territorial display but also for mate attraction and recognition of partners in the wild.

Males tend to call more frequently during breeding season, during which they become highly territorial and defend an area that includes the nesting site and feeding grounds. Additionally, the Brush Cuckoo is known to engage in mimicry of other bird sounds, presumably for camouflage or as a territorial display.


In summary, the Brush Cuckoo species feeds primarily on insects, searching for its prey in shrublands and the understory of forests. The species’ diet is opportunistic, and it can adjust its food to the prevalence of different prey items.

The metabolic rate of Brush Cuckoos is relatively low, with slight influences from external conditions. Finally, the Brush Cuckoo has a distinctive vocalization with six different types of calls.

The loud whip whistle is often the most recognizable of these calls, used for territorial display, mate attraction, and recognition of partners. The species’ ability to mimic the sounds of other bird species for camouflage or territorial display is noteworthy.


Locomotion: Brush Cuckoos are arboreal, meaning they spend most of their time in trees and shrubs. The species moves through the understory of the forest with relative ease, using a combination of hopping, climbing, and flight.

Brush Cuckoos are primarily ground foragers and have shorter wings than other cuckoo species to facilitate their foraging style in dense vegetation. Self Maintenance: Brush Cuckoos exhibit a high degree of self-maintenance behavior, with frequent preening at rest.

This behavior ensures that the feathers remain in good condition, maximizes their aerodynamic efficiency for flight, and helps to protect feathers from parasites. Agonistic

Behavior: The Brush Cuckoo is territorial during the breeding season, defending its territory vigorously against other birds and conspecifics.

Brush Cuckoos use a range of visual, vocal, and physical displays, such as wing flicking, vocalizations, and chasing to defend their nesting site and foraging grounds. Sexual

Behavior: The Brush Cuckoo has a polygynous mating system, where males mate with more than one female.

During the breeding season, males become highly territorial and defend an area that includes the nesting site and feeding grounds. Males have been observed to court females by hopping around them and emitting their whip-whistle calls.

Courtship displays differ between subspecies, with Philippine subspecies of the Brush Cuckoo singing a series of melodic phrases to woo a female.


The Brush Cuckoo’s breeding season is highly seasonal, usually lasting from March to September.

Breeding is highly correlated with the onset of the wet season in most parts of its range, which likely influences food resource availability and insect abundance.

Brush Cuckoos typically have monogamous mating systems in which the males court the females through displays and call behavior. The Brush Cuckoo builds its nest within vegetation, conveniently hidden from predators.

The nest is a shallow structure made up of a few small twigs that form a platform for incubation. Both males and females incubate the eggs, which typically number two.

The incubation period is usually around seventeen days, with the eggs hatching sequentially. The chicks remain in the nest for up to three weeks, with both parents foraging for food to feed them.

Demography and Populations

The Brush Cuckoo species is not considered a globally threatened species, with a stable population trend overall. However, population sizes are decreasing in some areas due to habitat loss and degradation.

The global climate change may also influence the species’ range and population viability in certain areas. Brush Cuckoos have an opportunistic dietary behaviour, which may help facilitate their ability to adapt to changing food resources and abiotic factors.

Demographic studies of the Brush Cuckoo species have revealed that the population structure consists of different demographic groups (adult

Popular Posts