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. It is part of the family Dicruridae and has 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. These birds nest close to wetlands, forests, and farms and the breeding season varies depending the region. The female usually lays one to four eggs, which hatch in 15 to 18 days.
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 known for their aggressive and fearless behavior, often attacking and driving away much larger animals, including birds of prey, when their nest is in danger. Due to its extensive range and stable population, the fork-tailed drongo is classified by the IUCN Red List as a least-concern species.
Taxonomy
The fork-tailed drongo was described by Johann Matthäus Bechstein in 1794. and four races are usually accepted, though as of 2023, D. a. divaricatus and D. a. lugubris are included within the taxon by the IOC. The races D. a. modestus, together with D. a. coracinus and D. a. atactus are usually split as a separate species, the velvet-mantled drongo, D. modestus (Hartlaub, 1849).
- D. a. apivorus <small>Clancey, 1976</small>
::Range: Gabon, Congo Republic, DRC, Angola, northwestern Zambia, Namibia, Botswana and northwestern South Africa;
::Description: primary remiges with brown outer vanes and pale inner vanes (noticeable while perched and in flight respectively); 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.
Description
The bird possesses a robust black beak and red eyes. When born, they lack feathers, exhibiting reddish skin, an orange beak, yellow gape flange, brown eyes, and a black beak. Juvenile fork-tailed drongos are dark brown tone with some buff-colored feather tips, a less pronounced tail fork, brown or grey eyes, and a pale mouth. While resembling adults, they lack the glossy shine on the lower body and display pale feathers on certain areas. Both sexes share a black body with a blue-green iridescence in specific regions. The underside, including the belly, is uniformly black, contrasting with the glossy black-blue upper body. Instances of leucism have been observed in the fork-tailed drongo.
Vocalizations
This bird is notably vocal, often commencing the dawn chorus and often is the last heard at dusk. Their pre-dawn calls comprise variations such as jwaaa-jwaaa and jeewy-jeeerr. They exhibit a diverse repertoire of vocalizations, ranging from sharp calls, brief whistles, and squeaks to fluid, raspy, and scratchy notes delivered rapidly or with extended pauses. Their repertoire includes calls like chyup, tjaaa, the resounding jer-woo, and the whistled jee-lu. Mated pairs participate in coordinated duets lasting 4–5 minutes. Their songs feature soft, high-pitched, nasal, or melodious whistles, chirps, grinding sounds, and liquid chattering. such as bocage's bushshrike, thrushes, tchagras, bulbuls, birds of prey and owls. They have also been observed imitating the mewings of cats and the alarm calls of meerkats.
Typically, the fork-tailed drongo perches at a height ranging from to , adopting an erect posture from which they swiftly pursue insects by flycatching, plunge diving, or seizing them on the ground before returning to the same branch. This species is capable of holding large items with their claws and rending them with their bills. They frequently inhabit savanna fires, where they capture fleeing insects and other prey seeking refuge from the flames.
Kleptoparasitism
A tactic employed by the fork-tailed drongo to acquire food is an opportunistic kleptoparasitism. The drongo will give genuine alarm calls to signal the presence of predators to other animals, but occasionally, it will issue a false alarm call to displace those animals and steal their food.
It has been observed that fork-tailed drongos spend approximately 29% of their time trailing other animals. Species such as southern pied babblers, sociable weavers, wattled starlings and meerkats, which forage on the ground, are often targeted by fork-tailed's kleptoparasitism. This behavior arises because drongos lack the necessary morphological adaptations to effectively hunt certain prey that are more nutritious and calorific, hence resorting to kleptoparasitism. These birds frequently assume leadership roles in mixed-species foraging flocks, serving as sentinels alongside other species. This cooperative strategy reduces the risk of predation and enhances the foraging success of the associated species. Simultaneously, the drongo exploits these associations to increase opportunities for kleptoparasitism. Approximately a quarter of their food intake is estimated to result from kleptoparasitism, with an additional 10% acquired by capturing prey flushed by associated species. Furthermore, the prey caught using this strategy are typically larger than those acquired through self-foraging. Drongo eggs display a diverse array of colors and patterns, which the cuckoos mimic. Experiments indicate that drongos can detect and reject 93.7% of introduced eggs.
Conservation status
Due to their very large range, stable population trend and size, the fork-tailed drongo is considered to be a least-concern species by the IUCN Red List, though the subspecies D. a. modestus, previously considered a separated species, was considered a near-threatened. The fork-tailed drongo faces threats from pesticide use, which diminishes their prey availability, and habitat destruction due to farmland expansion.