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5 Fascinating Facts about the Black-thighed Falconet

The Black-thighed Falconet, also known as Microhierax fringillarius, is a small falcon found in Asia. Despite its diminutive size, this bird is a fierce predator, preying on insects, small reptiles, and other small birds.

In this article, we will delve into the identification, plumage, and behaviors of this fascinating bird in order to gain a greater appreciation for its unique characteristics.


Field Identification

The Black-thighed Falconet is a small, compact bird, usually measuring about 15cm in length. Its head is round, with a short, curved beak and large, dark eyes.

Its wings are short and pointed, and its tail is squared-off at the base. The birds plumage is characterized by a russet-brown head and body, a white belly, and black thighs.

Its wings have distinctive black and white markings.

Similar Species

The Black-thighed Falconet belongs to a group of small falcons that are often difficult to tell apart. In particular, the bird is similar in appearance to the Collared Falconet (Microhierax caerulescens).

However, the Black-thighed Falconet can be distinguished by its black thighs and the lack of a collar on its neck. Additionally, the markings on its wings are slightly different from those of the Collared Falconet.



Like all birds, the Black-thighed Falconet goes through different stages of plumage known as molts. There are two main molts: the pre-basic molt and the pre-alternate molt.

During the pre-basic molt, which occurs in the late summer or early fall, the bird replaces all of its feathers. This molt results in a more subdued plumage, with fewer bright colors.

In contrast, the pre-alternate molt occurs in the spring and summer, and results in more colorful or striking plumage. This helps birds to attract mates during the breeding season.



As mentioned earlier, the Black-thighed Falconet is a fierce predator. It is known to hunt a wide variety of prey, including insects, small reptiles, and other birds.

It is especially skilled at capturing insects in mid-air, using its sharp talons to pluck them out of the sky. It is also known to perch on high branches or other vantage points, scanning the area for potential prey.


The Black-thighed Falconet breeds during the winter months, making its nest in the hollow of a tree or a rock crevice. The female lays a clutch of two eggs, which are incubated by both parents for about 25 days.

After hatching, the chicks are fed a diet of insects and other small prey by both parents. They fledge after about 30 days, and become independent after a few months.


Overall, the Black-thighed Falconet is a fascinating bird with many unique characteristics. Its distinctive plumage, fierce hunting skills, and interesting breeding behaviors are just a few of the reasons why bird enthusiasts are drawn to this species.

By learning more about the Black-thighed Falconet, we can gain a greater appreciation for the diversity and complexity of the natural world.

Systematics History

The Black-thighed Falconet (Microhierax fringillarius) is classified in the family Falconidae and is a member of the genus Microhierax. The Falconidae family includes birds of prey, divided into diurnal and nocturnal birds.

The diurnal birds of prey, or falcons, include the Black-thighed Falconet. In the past, the genus Microhierax was included in the family Falconinae, which at that time included only falcons, but molecular studies proved that the genus should have a familial level recognition.

Geographic Variation

The Black-thighed Falconet is distributed in Asia, where it inhabits the tropical forests of the Indian Subcontinent, Southeast Asia, and the Indonesian Archipelago. Its range extends from the foothills of the Himalayas in the north to the lower Mekong region in the south.

Moreover, the Black-thighed Falconet is also found in the islands of Sumatra, Java, Borneo, and the Philippines. This geographic variation in distribution has resulted in some unique characteristics and subspecies differentiation.


There are three recognized subspecies of the Black-thighed Falconet: M. f.

fringillarius, M. f.

ceylonensis, and M. f.

saturatus. The subspecies M.

f. fringillarius is found from Nepal and northern India to southern China, Thailand, and Indochina.

The subspecies M. f.

ceylonensis is found only on the island of Sri Lanka, while M. f.

saturatus is found in the Malaysian states of Sabah and Sarawak and on the Indonesian island of Borneo. The subspecies differentiation is based on the size and color of the bird.

M. f.

fringillarius is the largest subspecies, with a more heavily streaked plumage pattern. The male has a dark brown head with rust-colored nape and mantle.

The underparts are white with dark streaks on the breast and flanks. The female is similar but has a more contrasting head pattern.

M. f.

ceylonensis is a smaller subspecies, with a paler plumage pattern and less prominent markings on the underparts. The male has a brown head and underparts are off-white with sparse streaks and the female has a slightly brighter underpart than the male.

In contrast, M. f.

saturatus is larger than M. f.

ceylonensis, but smaller than M. f.

fringillarius. This subspecies has a more brightly colored plumage, with a cinnamon rump, brighter yellow underparts, and a white throat.

Related Species

There are several other species in the genus Microhierax, including the Philippine Falconet (M. erythrogenys), the Sunda Pygmy Falcon (M.

latifrons), and the White-rumped Falcon (M. insignis).

The Philippine Falconet is found only in the Philippines and has a more distinctively red head, while the Sunda Pygmy Falcon is endemic to the Indonesian Archipelago. The White-rumped Falcon is distributed from eastern India to Southeast Asia and has a white rump, which distinguishes it from the Black-thighed Falconet.

Despite the close relationship of these species, their behaviors, habitats, diets, and vocalizations are different, which contributes to the different ecological niches of the species.

Historical Changes to Distribution

Despite being widespread across many parts of Asia, the Black-thighed Falconet has experienced changes to its distribution over time.

Habitat loss, primarily caused by deforestation, is the most significant threat to the survival of this species.

This has led to population declines and range contractions in all three subspecies. In Sri Lanka, where only one subspecies is found, forest loss and habitat degradation have resulted in decreased breeding success and a significant population decline.

Additionally, the illegal capture of this species for the pet trade has had an impact on its populations across its range. Climate change, particularly the alteration of seasonal patterns, could also have an impact on the bird’s distribution.

The Black-thighed Falconet, like many bird species, relies on the timing and abundance of food resources, as well as weather patterns, to breed and migrate. Changes in these patterns can have a significant impact on the species survival, causing a shift in its distribution.

In conclusion, the Black-thighed Falconet is a fascinating species of bird with unique characteristics that distinguish it from other birds of prey. Its geographic variation and subspecies differentiation have enabled it to adapt to various habitats, diets, and ecological niches.

However, ongoing habitat loss and other threats have had an impact on the bird’s distribution, and its survival relies on conservation efforts to protect its habitat and prevent further range contractions.


The Black-thighed Falconet is typically found in tropical deciduous forests, evergreen forests, and semi-evergreen forests, where there is a high concentration of trees and varied understory vegetation. These birds are also known to inhabit forest edges, agricultural lands, and grasslands.

Specifically, they can be found in foothills, plains, and low mountainous areas up to an elevation of 2000 meters. The species prefers forest edges or thinning forests where there is a mix of open space and forest canopy, which provides suitable habitat for the bird’s prey.

Moreover, the presence of nearby waterbodies, such as rivers, streams, or wetlands, is also essential as it supplies the increased food requirement during breeding. The availability of cavities in trees or rock crevices for nesting is also important, as Black-thighed Falconets are cavity nesters.

Movements and Migration

The Black-thighed Falconet is resident or sedentary in most parts of its range, although some local movements may occur in response to changes in food resources. These movements are usually associated with seasonal changes in the abundance of prey or reproductive activity rather than migration.

This species may move to areas with more resources as a response to the availability of suitable breeding sites or prevailing weather conditions. However, the Black-thighed Falconet’s movements and migration patterns can vary significantly depending on its range and subspecies.

For instance, in Malaysia, the subspecies M. f.

saturatus appears to be partially migratory, with some birds moving between different altitudes to take advantage of seasonal fluctuations in food resources. Moreover, in some areas, such as southern Vietnam, the species may move to lower elevations for the breeding season.

In contrast, the subspecies M. f.

ceylonensis is largely sedentary, as Sri Lanka’s relatively small landmass does not provide enough space for long-distance movements. On the other hand, M.

f. fringillarius shows seasonal movements related to breeding.

In northern India and Nepal, it is a winter visitor, arriving in the fall and leaving during the spring. In Southeast Asia, it is a resident, although some birds may move to higher altitudes during the non-breeding season.

During the breeding season, the Black-thighed Falconet has a specific territory where it breeds and hunts. These territories can vary in size and are typically defended by both the male and female.

In summary, the Black-thighed Falconet is primarily a resident bird that may move locally in response to changes in prey availability or reproductive activity, with subspecies showing varying degrees of migratory or sedentary behavior. Understanding the seasonal movements and migration patterns is crucial for the conservation of this species, especially in ensuring suitable habitats are available during the breeding seasons.

Diet and Foraging


The Black-thighed Falconet is an active and aggressive predator that hunts a variety of small prey, including insects, reptiles, and other birds. It feeds mainly on insects, including grasshoppers, beetles, butterflies, and dragonflies, which it captures on the wing by making short sallies, hovering, or flying from a perch.

It uses its sharp talons to catch and hold onto prey, which it then consumes in flight or on a perch. The bird’s unique hunting technique allows it to take prey rapidly and efficiently, enabling it to catch flying insects with greater certainty.


The Black-thighed Falconet’s diet varies depending on the subspecies, geographic location, and availability of food resources. In Southeast Asia, the bird typically feeds on insects, with beetles and grasshoppers being the most common prey.

Similarly, in Sri Lanka, the bird’s diet primarily consists of insects such as cicadas and grasshoppers. In contrast, M.

f. fringillarius in northern India and Nepal feeds on a wider variety of prey, including small birds.

Some subspecies, such as M. f.

saturatus in Malaysia, feed on reptiles such as lizards and skinks. Overall, the Black-thighed Falconet has a diverse diet that allows it to utilize the resources available in its habitat effectively.

Metabolism and Temperature Regulation

The Black-thighed Falconet has a high metabolic rate, which enables it to maintain a high internal body temperature necessary for best flying and hunting performance. Consequently, this species is adapted to cope with high ambient temperatures and humid environments.

When the body temperature rises, the bird pants, spreading its wings and opening its bill, which allows heat to be dissipated through evaporation. Moreover, the Black-thighed Falconet’s plumage aids in thermoregulation by insulating the bird from external temperatures.

Sounds and Vocal Behavior


The Black-thighed Falconet has a variety of vocalizations, including soft whistles, trills, and chattering calls. The bird uses these calls for communication, attracting mates, and establishing territory boundaries.

During the breeding season, males perform display flights, accompanied by loud whistle and chattering calls, to attract females and establish a territory. Similarly, females produce trilling calls to indicate readiness to mate or to call for a male’s attention.

The birds calls are often high-pitched and repeated continuously, often sounding like a musical series. In addition, the vocalization of the Black-thighed Falconet can vary by geographic location.

For example, the subspecies M. f.

fringillarius has a slightly different call structure compared to M. f.

saturatus and M. f.

ceylonensis. By analyzing these differences in vocalization, researchers can gain insight into the bird’s behavior, ecology, and taxonomy.


Overall, the Black-thighed Falconet is an astonishing bird species with unique characteristics that have enabled it to adapt to varied ecological niches. Its hunting techniques, diet, thermoregulation, and vocalizations, have contributed significantly to its survival in the wilds of Asia.

By understanding these aspects of the Black-thighed Falconet’s biology, we can gain a greater appreciation for the complexity and diversity of the natural world.



The Black-thighed Falconet displays remarkable agility and speed in flight, uncommonly swift and precise in its movements, which makes it an efficient predatory bird. It typically flies with a series of fluttering wing beats, interspersed with short glides, weaving around obstacles and making sudden turns as it pursues its prey.

They can also hover for several seconds to catch their prey during their hunting flights. Their short wings allow them to maneuver effortlessly between trees in forested habitats.

Self Maintenance

The Black-thighed Falconet is fastidious in its behavior and is regularly observed preening plumage to keep feathers well-oiled and remove dirt and parasites. For this purpose, they use their bill and the oil secreted by a gland on their lower back to maintain the quality of their feathers.

In addition to routine preening, Black-thighed Falconets also bathe in water or dust to remove dirt and parasites thoroughly.

Agonistic and Sexual Behavior

The Black-thighed Falconet displays a variety of agonistic and sexual behaviors. During the breeding season, males establish territories with displays and calls, which are used to attract females and deter other males.

Territory boundaries are rigorously defended, and neighbors often confront each other over invasion attempts. The bird employs a series of ritualized displays, including bowing, chasing, and posturing to communicate with other individuals.


The breeding season of Black-thighed Falconets varies depending on location, with birds breeding between November and June in India, and between May and August in Southeast Asia. Females select nest sites, which are typically cavities in trees or rocks, and both males and females participate in nest building.

The nests are made up of leaves, twigs, and other small debris in the cavity. The female lays two to three eggs and incubates them for about 26 days.

Both parents take turns incubating the eggs and chicks fed by both in the nest. The chicks hatch, covered with down, and become fully feathered in 22 to 30 days.

The adults continue to feed and take care of the chicks until they are ready to leave the nest, which takes about 30 to 35 days. Once the chicks are weaned, they accompany their parents to learn how to hunt and establish their territories.

Demography and Populations

The Black-thighed Falconet is widespread across its range, but its population size is unknown, and habitat loss has had an impact on its populations. Populations of this species are declining primarily due to deforestation and habitat loss, resulting from logging, agriculture, and human intervention.

Moreover, the illegal pet trade is also a significant threat to the species. In response to these threats, conservation measures aim to preserve suitable habitats and protect this species’ nesting and foraging sites.

The Black-thighed Falconet has been classified as Least Concern by the International Union for Conservation of Nature (IUCN) due to its vast range and population size. However, continued monitoring and conservation efforts are needed to ensure the persistence of this species in the wild.

By protecting its habitats, encouraging sustainable land use practices, and enforcing laws against poaching, the Black-thighed Falconet can continue to be appreciated for its unique adaptations, behaviors, and ecological roles.

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