The fork-tailed drongo (Dicrurus adsimilis), also called the common drongo or African drongo, is a small bird found from the Sahel to South Africa that lives in wooded habitats, particularly woodlands and savannas. They are part of the family Dicruridae and have four recognized subspecies, D. a adsimilis, D. a. apivorus, D. a. fugax and D. a. jubaensis. Like other drongos, the fork-tailed is mostly insectivorous; its diet mainly consists of butterflies, termites, and grasshoppers.
Physically, this species is characterized with a narrow fork-shaped tail, red-brownish eyes, and black plumage throughout all of its body.
The fork-tailed drongo is known for its ability to deceptively mimic other bird alarm calls in order for a certain animal to flee the scene so it can steal their food (kleptoparasitism). They are also notorious for displaying an aggressive and fearless behaviour by attacking and chasing off much larger animals, including birds of prey, when their nest or young are threatened. Due to its extensive range and stable population, the fork-tailed drongo is classified by the IUCN Red List as a least-concern species.
The fork-tailed drongo is a common and widespread resident breeder in Africa south of the Sahara. These insect-eating birds are usually found in open woodland, savanna and forest edge and are tolerant of arid climates. Its range was formerly considered to include Asia, but the Asian species is now called the black drongo (D. macrocercus). The bird can be found at heights as high as 2200 meters.
The bird has a robust black beak and red eyes. Young birds are born without feathers, with reddish skin, an orange mouth, yellow gape flanges, brown eyes and a black beak. Adolescent birds are dark brown with a few buff-colored feather tips, less defined tail fork, brown or grey eyes, and a pale-colored mouth. They look similar to adults but lack shine on the lower body and have pale feathers on certain parts. Both males and females have black bodies with a blue-green sheen on certain areas. The belly and lower body are entirely black in contrast to the glossy black-blue upper body. The long tail is deeply forked and black. The tail measures around 115–126 mm in length and 19–23 mm in depth. They have short legs and a wingspan of 134 mm. These birds have a bill depth of 0,4 mm and a bill length of 2.8 mm.
After breeding, adult birds undergo a full molt, typically occurring from December to March in Southern Africa and varying months in other regions. Young birds retain their immature plumage until the next breeding season. The post-juvenile molt is a partial process that begins before the growth of new wing and tail feathers after the nesting period. Leucism has been spotted in the fork-tailed drongo.
This specie is mostly insectivorous and occasionally eats fishes and other birds, furthermore they may take nectar and eat plants when available too. Predominant preyed animals are butterflies, beetles, caterpillars, grasshoppers, honey bees, moths, termites and weevils, especially common species being the angola white lady, macrotermes natalensis, cyrtacanthacris aeruginosa, and the desert locust. Sometimes they might also eat small fishes by swooping down from a perch hovering over water and dipping, it has been observed small birds being captured with their claws or bills, namely the bronze mannikin. Plants take around 15% of their diet, usually eaten are the moringa oleifera, azadirachta indica and the dialium guineense. These birds are solitary in its hunting. This species spends about 62% of the day feeding during the dry season, and 56% of the day during rainy seasons.
Usually, the fork-tailed drongo perches, from a height of 5 m (16 ft 5 in) to 7 m (22 ft 11+1⁄2 in), in an erect pose from which they rapidly charge insects flycatching, plunge diving or grabbing it on the ground and then return to the same branch. The specie can hold large items with their claws and tear them with their bills; removes wings of butterflies. They frequent savanna fires, where they catch fleeing insects and other prey running from the flames. These birds have a commensalist relationship with large mammals, following animals such as elephants and giraffes that disturb insects from the surrounding area, flushing out the prey.
Kleptoparasitism
A common employed tactic by the fork-tailed drongo to get food is kleptoparasitism. The drongo will give genuine alarm calls to alert the presence of predators to other animals, but sometimes it will give a false alarm call to displace those animals and steal their food. These birds may also outright attack other species or do so after a false alarm failed.
It has been observed that fork-tailed drongos spend a quarter of their time following other animals. Species, such as southern pied babblers, sociable weavers, wattled starlings and meerkats that forage on the ground are frequent victims of the fork-tailed kleptoparasitism, because the drongos don't possess the appropriate morphological adaptations to hunt certain preys that are more nutritious and calorific so they use kleptoparasitism. These birds frequently take the lead in mixed-species foraging flocks, acting as sentinels alongside to other species. This strategy reduces the risk of predation and enhances foraging success of these associated species. Simultaneously, the drongo capitalizes on these associations to increase opportunities for kleptoparasitism.
Though in doubt, researchers have considered the possibility that these drongos possess theory of mind, not fully shown in any animal other than humans.Approximately a quarter of their food intake is estimated to come from kleptoparasitism, and an additional 10% is acquired by capturing prey flushed by associating species. Moreover, the prey caught using this strategy are typically larger than those acquired through self-foraging. In response to a false alarm, the drongo will issue an 'all clear' call and escalate the rate of true alarms to counteract the effects of its manipulation.
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