Bird O'clock

10 Fascinating Facts About the Nankeen Kestrel

The Nankeen Kestrel, also known as the Australian Kestrel or the Windhover, is a small bird of prey that can be found throughout Australia, New Zealand, and parts of Southeast Asia. With its striking plumage and sharp hunting instincts, this bird is a formidable predator in the skies.

In this article, we will dive into the identification, plumages, and molts of this fascinating species.

Identification

Field Identification

The Nankeen Kestrel has a distinctive appearance, making it relatively easy to identify in the field. They are small birds, measuring around 30cm in length, with a wingspan of around 60cm.

They have long, pointed wings and a short tail that they use to steer and maneuver in the air. Their plumage is predominantly reddish-brown, with white undersides and black spots.

Juvenile birds have more muted colors and lack the black spots on their undersides.

Similar Species

While the Nankeen Kestrel is unique in its coloration and markings, it can be confused with other birds of prey, namely the Black-shouldered Kite and the Whistling Kite. The Black-shouldered Kite is slightly larger than the Nankeen Kestrel and has a distinctive white head and black shoulder patches.

The Whistling Kite is much larger, with a wingspan of up to 1.5 meters, and has a predominantly brown plumage with a pale head and neck.

Plumages

The Nankeen Kestrel has several plumage variations throughout its life cycle. Adult birds have a reddish-brown back and white underparts, with black spots on the undersides.

They also have a black facial mask and a distinctive blue-grey beak. Juvenile birds have a more muted coloration, with browns and greys rather than reds, and lack the black spots on their undersides.

As they mature, they develop their adult plumage, usually around one year of age.

Molts

Like most birds, the Nankeen Kestrel goes through molting cycles to replace old or worn feathers. They go through two major molts each year, replacing their feathers in an orderly pattern from the head down to the tail.

The first molt occurs after breeding season, typically around March or April, while the second molt occurs in the late summer or early fall, usually around August or September.

Key takeaways

– The Nankeen Kestrel is a small bird of prey found in Australia, New Zealand, and Southeast Asia. – They can be identified by their reddish-brown plumage, white undersides, black spots, and blue-grey beak.

– Juvenile birds lack the black spots and have a more muted coloration. – The Nankeen Kestrel goes through two major molts each year, replacing feathers in an orderly pattern from the head down to the tail.

Systematics History

The Nankeen Kestrel, also known as the Australian Kestrel, Falco cenchroides, belongs to the Falconidae family, which includes other falcon species such as the Peregrine Falcon, Kestrels, and Falcons. The systematic classification of the Nankeen Kestrel has gone through several changes throughout history.

In the past, the Nankeen Kestrel was considered to be a subspecies of the Common Kestrel (Falco tinnunculus). However, genetic studies have shown that the Nankeen Kestrel is a distinct species and therefore, was reclassified as Falco cenchroides in 1902.

Geographic Variation

The Nankeen Kestrel is widely distributed throughout Australia, New Guinea, and parts of Southeast Asia. Due to its extensive range, several geographic variations within the species have been identified, particularly in their size and coloration.

In northern Australia, the Nankeen Kestrel is larger in size compared to those found in southern and western parts of the continent. In Indonesia, especially in Bali and Sulawesi, the Nankeen Kestrel is smaller in size compared to those found in Australia.

The Indonesian Nankeen Kestrel also has a darker appearance and lacks the black markings on the wings seen in the Australian birds.

Subspecies

Currently, six subspecies of the Nankeen Kestrel are recognized. They are Falco cenchroides cenchroides, F.

c. natalis, F.

c. punicus, F.

c. subniger, F.

c. dichroa, and F.

c. rufescens.

These subspecies are primarily differentiated by their size and coloration. Falco cenchroides cenchroides is the nominate subspecies and can be found throughout most of Australia.

They are the largest subspecies with a length of up to 35cm. Falco cenchroides natalis is found in New Guinea, and is the smallest subspecies.

They have a more orange-brown coloration than other subspecies. Falco cenchroides punicus is found in Indonesia and is smaller in size than those found in Australia.

They have a darker appearance with less prominent black markings on their wings. Falco cenchroides subniger is found throughout arid regions of Australia.

This subspecies has a darker appearance overall, with prominently black-streaked white underparts. Falco cenchroides dichroa can be found in southern and southeastern Australia.

They have a paler appearance compared to other subspecies, with less distinct black markings on their wings. Falco cenchroides rufescens is found in Tasmania, an island state of Australia.

They have a reddish-brown appearance, with less white on their underparts compared to other subspecies.

Related Species

The Nankeen Kestrel is closely related to other kestrel species, such as the Common Kestrel (Falco tinnunculus) of Europe and the Lesser Kestrel (Falco naumanni) of Africa. However, genetic studies have shown that the Nankeen Kestrel is more closely related to the American Kestrel (Falco sparverius) than to other Kestrel species.

Historical Changes to Distribution

The distribution of the Nankeen Kestrel has undergone significant changes throughout history. The species was once widespread across mainland Australia, but has since become scarce in some areas due to habitat destruction and declining prey populations.

In the past, the Nankeen Kestrel was found in Tasmania, but became extinct on the island in the 1960s. The species was reintroduced to Tasmania in the 1980s, and is now considered to be a breeding resident on the island.

The Nankeen Kestrel has also undergone changes in its distribution in response to climate change. As temperatures increase, the species has shifted its range southwards in search of cooler temperatures.

This range shift has resulted in the species declining in some areas while expanding in others.

Key takeaways

– The Nankeen Kestrel belongs to the Falconidae family and was reclassified as Falco cenchroides in 1902. – The species is widely distributed throughout Australia, New Guinea, and parts of Southeast Asia and has several geographic variations in size and coloration.

– Currently, six subspecies of the Nankeen Kestrel are recognized, primarily differentiated by their size and coloration. – The Nankeen Kestrel is closely related to other kestrel species, but is more closely related to the American Kestrel than to other Kestrel species.

– The distribution of the species has undergone significant changes throughout history, due to habitat destruction, declining prey populations, and climate change.

Habitat

The Nankeen Kestrel can be found in a wide range of habitats, including open grasslands, savannas, woodlands, and coastal areas. However, they are particularly associated with open farmland, where they hunt for small mammals, birds, and insects in the fields and along roadways.

The species has adapted to human-modified landscapes and can often be spotted perched on powerlines, fence posts, and telephone poles in rural and urban areas. Despite their high tolerance for human presence, the species is sensitive to habitat fragmentation and can suffer population declines when their habitat is broken up into smaller, isolated patches.

Movements and Migration

The Nankeen Kestrel is generally considered a non-migratory species, but they do exhibit some local movements and seasonal fluctuations in their range. These movements are driven by changes in food availability and breeding behaviors.

During the breeding season, from June to December, the Nankeen Kestrel becomes more territorial and spends more time hunting and defending its territory. This can lead to local movements as individuals move further afield in search of prey.

During the non-breeding season, from January to May, the species may become more nomadic and move more widely in search of food. In some regions, they may also move to higher elevations in the cooler months.

While the Nankeen Kestrel is mostly non-migratory, some individuals have been found to undertake short-distance migrations. These movements are more commonly observed in juveniles and can occur in response to changes in food availability or environmental conditions.

An example of this is the seasonal migration of Nankeen Kestrels in the Northern Territory of Australia. In the dry season, the birds move to the coast in search of food, and return inland during the wet season when food is more abundant in the grasslands.

Migration behavior is also linked to population genetics. In a study of Nankeen Kestrels in Australia, genetic analysis showed that birds from the northern latitudes exhibited a higher degree of migration behavior compared to those from southern populations.

Overall, while the Nankeen Kestrel is mostly a non-migratory species, there are some local movements and short-distance migrations exhibited by the species throughout their range. These movements are driven by changes in food availability, breeding behaviors, and environmental conditions, and can vary between different populations.

Key takeaways

– The Nankeen Kestrel inhabits a wide range of habitats, including open farmland, grasslands, savannas, woodlands, and coastal areas. They are adaptable to human-modified landscapes, but can be sensitive to habitat fragmentation.

– The species is generally considered non-migratory, but exhibits some local movements and seasonal fluctuations in their range in response to changes in food availability and breeding behaviors. – While short-distance migrations have been observed in some populations, migration behavior is generally linked to population genetics and varies between different populations.

Diet and Foraging

Feeding

The Nankeen Kestrel is a diurnal hunter and an opportunistic feeder, preying on a variety of animals, including small mammals, birds, reptiles, and insects. They have keen eyesight, and scan the ground from a perch or high flight to locate prey.

Once prey is spotted, they will descend swiftly and capture it in their talons. The species exhibit a variety of hunting techniques, including hovering, perch hunting and ground hunting.

Hovering is the most commonly observed hunting behavior in the species, where the bird will remain airborne, using its wings to maintain a stable position while scanning for prey below. Perch hunting is another common hunting behavior, where the bird will scan the ground from a perch, such as a fence post or telephone pole.

Once prey is spotted, the bird will launch itself into the air and descend upon the prey quickly. Ground hunting is less commonly observed and usually involves hunting insects or small rodents that are active on the ground.

Diet

The Nankeen Kestrel has a varied diet, and the prey they consume differ depending on their location and the availability of prey. In Australia, the species predominantly feeds on small mammals such as rodents and rabbit, but will also take insects, reptiles, and small birds.

In Southeast Asia, their diet is comprised of insects, small birds, and small mammals such as mice and rats. In New Guinea, they are known to prey on a variety of lizards, small birds, and insects.

Metabolism and Temperature Regulation

Like all birds, the Nankeen Kestrel is endothermic, meaning they maintain a constant body temperature through metabolic processes. In order to maintain their body temperature, their metabolism is high, which requires a steady supply of nutrients.

To account for the high energy demands of their metabolism, the species has adapted to a high protein diet, consisting of prey rich in amino acids. This high protein diet allows the species to maintain their body temperature during periods of low ambient temperature, such as during the cool winter months.

To further help regulate their temperature, the Nankeen Kestrel exhibits behavioral thermoregulation. This behavior involves postural changes that expose different regions of their body to either the sun or shade, depending on the temperature.

By altering their posture, they can regulate heat loss and gain from their body.

Sounds and Vocal Behavior

Vocalization

The Nankeen Kestrel has a variety of vocalizations that they use to communicate with each other and establish their territory. They have a distinctive, high-pitched whistling call that can be heard during flight, and a harsh, screeching call when engaging in territorial disputes.

One vocalization commonly observed in the species is the chittering call. This call is used in social interactions and often heard when individuals are sharing food or roosting together.

Additionally, the species exhibits a softer chirruping call when communicating with their mate or young. During the breeding season, the male Nankeen Kestrel will also perform a courtship display, which includes vocalizations and aerial acrobatics.

The male will perch near the female and produce a high, squealing call while flapping his wings and elevating his body. This behavior is used to attract a mate and establish a breeding pair.

In summary, the Nankeen Kestrel is a diurnal hunter and opportunistic feeder, preying on a variety of animals, including small mammals, birds, reptiles, and insects. They have a high metabolism and exhibit behavioral thermoregulation to regulate their body temperature.

The species exhibits a variety of vocalizations, including high-pitched whistling calls, screeching calls during territorial disputes, and softer chirruping calls during communication with their mate or young. The male also performs a courtship display which includes high-pitched vocalizations and aerial acrobatics.

Behavior

Locomotion

The Nankeen Kestrel is a very agile flier, with a fast, direct flight that is well-adapted for hunting. They use their long, pointed wings to soar high in the air while searching for prey and glide with their wings outstretched during hunting dives or descents.

They are also capable of hovering in the air for extended periods of time, allowing them to observe the ground below for potential prey. On the ground, the species is also quite agile, running swiftly on their strong legs while pursuing prey or during territorial displays.

Self Maintenance

The Nankeen Kestrel exhibits typical self-maintenance behaviors of most birds. They regularly preen their feathers, using their beak to clean individual feathers and remove feather parasites.

They also occasionally take dust baths to clean their feathers and help to control mites and lice.

Agonistic Behavior

The Nankeen Kestrel exhibits agonistic behavior during territorial disputes or when other birds or predators enter their territory. They will chase, dive, and use vocalizations to drive away intruders.

In addition, males will engage in agonistic behavior during the breeding season to establish and defend their territory from other males.

Sexual Behavior

The Nankeen Kestrel has a monogamous breeding system, with pairs remaining together for the breeding season and potentially for multiple seasons. The male will perform an elaborate courtship display to attract a mate, which includes aerial acrobatics, vocalizations, and presents of food.

During copulation, the male will mount the female from behind and hold onto her with his talons. The pair will remain connected for a few seconds before separating.

Breeding

Breeding in the Nankeen Kestrel occurs once a year, during the austral winter and spring months. Males and females both reach sexual maturity at around one year of age.

The male will establish and defend a breeding territory, using vocalizations and aerial displays to attract a mate. Nests are typically constructed in tree hollows, cliffs, or artificial nest boxes.

Both parents contribute to nest construction and incubation. The female will lay a clutch of 2-5 white or cream-colored eggs, which are incubated by both parents for around 30 days.

Chicks are born with a soft downy plumage and are cared for by both parents. The male brings food to the female and chicks during the early stages of the chick’s development, while the female remains on the nest to protect and brood the chicks.

After around 35-40 days, the chicks fledge and leave the nest. They will remain dependent on their parents for around a further 30-45 days before becoming independent.

Demography and Populations

The Nankeen Kestrel has a stable population and is classified as a species of least concern by the International Union for Conservation of Nature (IUCN). However, in some regions, the species has been affected by habitat fragmentation and declining prey populations.

In Tasmania

Popular Posts