Fork-tailed drongo
D. a. fugax pictured in Rwanda, and song of nom. subspecies, South Africa
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Dicruridae
Genus: Dicrurus
Species:
D. adsimilis
Binomial name
Dicrurus adsimilis
(Bechstein, 1794)

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.

Taxonomy

Described by Johann Matthäus Bechstein in 1794. Its populations are genetically highly structured,[2] and four races are accepted.[3][4] As of 2023, D. a. divaricatus and D. a. lugubris are included within the taxon by the IOC.[5] The races D. a. modestus (Príncipe) together with D. a. coracinus and D. a. atactus (Bioko to west and central mainland Africa, from Guinea east to western Kenya and south to Angola) are usually split as a separate species, the velvet-mantled drongo, D. modestus (Hartlaub, 1849).

  • D. a. apivorus Clancey, 1976
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)[4]
Habitat: Arid savanna
  • D. a. fugax W.K.H.Peters, 1868
Range: Uganda, Kenya, Tanzania and Zanzibar, southeastern Zambia, Malawi, Mozambique, Zimbabwe, Botswana, eastern Eswatini and northeastern South Africa
Description: Smaller than nominate,[4] outer vanes of primaries brown, and inner vanes dark
  • D. a. adsimilis (Bechstein, 1794)
Range: western Eswatini, Lesotho and eastern to southern South Africa
Description: Darker remiges, especially noticeable in flight[4]
  • D. a. jubaensis van Someren, 1931
Range: Ethiopia, Eritrea, and Somalia
  • D. a. divaricatus (Lichtenstein, MHK, 1823) – Senegambia and south Mauritania to southwest Chad.[6]
  • D. a. lugubris (Hemprich & Ehrenberg, 1828) – south Chad to Eritrea, Ethiopia, north Kenya, and north Somalia.[6]

Distribution and habitat

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.[7] 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.[8]

Description

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.[8][9] 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.[10]

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.[9][11][12] Leucism has been spotted in the fork-tailed drongo.[13]

Vocalizations

These birds are highly vocal, often initiating the dawn chorus and being the last heard at dusk.[3] Pre-dawn calls include jwaaa-jwaaa and jeewy-jeeerr. They display a wide range of vocalizations, from sharp calls, short whistles, and squeaky sounds to liquid, grating, and scratchy notes delivered in rapid succession or with long pauses. Singing calls encompass chyup, tjaaa, loud jer-woo, and whistled jee-lu. Partners engage in synchronized duets lasting 4–5 minutes. Their songs can be characterized by soft, high-pitched, nasal, or melodious whistles, chirps, grinding sounds, and liquid chatters.[9]

These birds produce specific drongo calls and mimic other bird species[14][15] 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.[9]

Behavior

Feeding

This specie is mostly insectivorous and occasionally eats fishes and other birds, furthermore they may take nectar and eat plants when available too.[10][16] 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.[16][17] This species spends about 62% of the day feeding during the dry season, and 56% of the day during rainy seasons.[16]

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.[17][16] 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.[18]

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.[19] These birds may also outright attack other species or do so after a false alarm failed.[20]

It has been observed that fork-tailed drongos spend a quarter of their time following other animals.[21] 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.[22][23] 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.[7][23]

Though in doubt, researchers have considered the possibility that these drongos possess theory of mind, not fully shown in any animal other than humans.[15][24][25] 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.[21] 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[23]

Breeding

During the breeding season, these birds often nest close to wetlands, forests, and farms, benefiting from the favorable nesting sites and materials provided by the microhabitat and vegetation.[16] They exhibit monogamous behavior and are known for their aggressiveness towards other drongos, as well as nest predators like crows, birds of prey, hornbills, shrikes, small mammals, and large snakes. Partners perch together, performing duets, and displaying behaviors such as bowing and bobbing their heads. Brood parasitism on groundscraper thrush have been observed.[9]

The breeding season typically spans from March to September north of the equator and from September to January south of it. Egg-laying season varies greatly between regions. The number of broods ranges from one to four, and they may replace the clutch if lost early in the season. Nests are generally located 2.2 to 17 meters above the ground, built between horizontal branches, featuring saucer-shaped structures made with plant stems, lichens, small roots, tendrils, and cobwebs. Eggs are laid at intervals of 24 to 48 hours. Incubation, lasting 15 to 18 days, commences only after the clutch is complete. Both male and female feed the chicks, offering flies, beetle larvae, lizards, and seeds. The nestling period can range from 16 to 22 days.[9]

Drongos are commonly used as brood hosts for the African cuckoos (21.8% of nests), in the Kalahari Desert was found that Jacobin cuckoos also parasite the drongo.[26] Drongo eggs have a wide diversity of colours and patterns as a form of personal signature, which the cuckoos imitate. Experiments suggest that the drongos can identify and reject 93.7% of introduced eggs.[27]

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 subspecie D. a. modestus, previously considered a separated specie, 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.[1] However, the species is unlikely to be threatened in the near future as it benefits from tree clearance in dense forests.[9]

References

  1. 1 2 BirdLife International (2016). "Dicrurus adsimilis". IUCN Red List of Threatened Species. 2016: e.T103710902A95034217. doi:10.2305/IUCN.UK.2016-3.RLTS.T103710902A95034217.en. Retrieved 19 November 2021.
  2. ↑ Bowie, Rauri; Crowe, Tim; Voelker, Gary; et al. "Comparative phylogeography of southern African birds" (PDF). Annual Report January – December 2009, Research Programmes & Initiatives: Systematics and Biogeography. Percy FitzPatrick Institute, University of Cape Town. Retrieved 24 August 2016.
  3. 1 2 Rocamora, G.; Yeatman-Berthelot, D. (2016). "Fork-tailed Drongo (Dicrurus adsimilis)". Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. Retrieved 24 August 2016.
  4. 1 2 3 4 Chittenden, H.; et al. (2012). Roberts geographic variation of southern African birds. Cape Town: JVBBF. pp. 204–205. ISBN 978-1-920602-00-0.
  5. ↑ "IOC Master List v13.2". IOC World Bird List.
  6. 1 2 Gill, Frank; Donsker, David; Rasmussen, Pam. "Species Updates – IOC World Bird List". www.worldbirdnames.org. International Ornithological Committee. Retrieved 2023-07-25.
  7. 1 2 Morgan, Tc; McCleery, Ra; Moulton, Mp; Monadjem, A (August 2012). "Are Southern Black Flycatchers Melaenornis pammelaina associated with Fork-tailed Drongos Dicrurus adsimilis ?". Ostrich. 83 (2): 109–111. Bibcode:2012Ostri..83..109M. doi:10.2989/00306525.2012.690351. ISSN 0030-6525. S2CID 83726699.
  8. 1 2 "Birds of Kenya and northern Tanzania". Choice Reviews Online. 34 (05): 34–2756-34-2756. 1997-01-01. doi:10.5860/choice.34-2756. ISSN 0009-4978.
  9. 1 2 3 4 5 6 7 Kirwan, Guy M.; Rocamora, Gérard; Yeatman-Berthelot, Dosithée (2023). "Fork-tailed Drongo (Dicrurus adsimilis), version 2.0". Birds of the World. doi:10.2173/bow.fotdro5.02. ISSN 2771-3105.
  10. 1 2 Carnaby, Trevor (2008). Beat about the bush: Birds (1st ed.). Johannesburg: Jacana. pp. 572–573. ISBN 9781770092419.
  11. ↑ Osinubi, Samuel Temidayo (2016-05-20). "The Birds of Ghana: an Atlas and Handbook". Ostrich. 87 (2): 197–198. doi:10.2989/00306525.2016.1198973. ISSN 0030-6525.
  12. ↑ Dowsett, R. J; F., Dowsett-Lemaire (2019). The Birds of Benin and Togo. Sumène, France: Tauraco Press.
  13. ↑ Herremans, Marc; Herremans-Tonnoeyr, Diane (1997-04-01). "Social Foraging of the Forktailed Drongo Dicrurus adsimilis: Beater Effect or Kleptoparasitism?". Bird Behavior. 12 (1): 41–45. doi:10.3727/015613897797141344. ISSN 0156-1383.
  14. ↑ Flower, Tom (May 22, 2011). "Fork-tailed drongos use deceptive mimicked alarm calls to steal food". Proceedings of the Royal Society B: Biological Sciences. 278 (1711): 1548–1555. doi:10.1098/rspb.2010.1932. PMC 3081750. PMID 21047861.
  15. 1 2 Flower, Tom (2010). "Fork-tailed drongos use deceptive mimicked alarm calls to steal food". Proceedings of the Royal Society B. 278 (1711): 1548–1555. doi:10.1098/rspb.2010.1932. PMC 3081750. PMID 21047861.
  16. 1 2 3 4 5 E.F., Okosodo; J.O., Orimaye; O.S, Odewumi (2016). "Diet and Foraging Ecology of Fork Tailed Drongo (Dicrurusadsimilis) in Leventis Foundation Nigeria, Agricultural School South West Nigeria" (PDF). International Journal of Environment, Agriculture and Biotechnology: 252–256. doi:10.22161/ijeab/1.2.20.
  17. 1 2 Rocamora, Gérard; Yeatman-Berthelot, Dosithée (2020). "Fork-tailed Drongo (Dicrurus adsimilis), version 1.0". Birds of the World. doi:10.2173/bow.fotdro5.01. S2CID 216271598.
  18. ↑ Carnaby, Trevor (2013). Beat About the Bush: Mammals and birds. Jacana Media. ISBN 9781431408535.
  19. ↑ Flower, Tom (2011-05-22). "Fork-tailed drongos use deceptive mimicked alarm calls to steal food". Proceedings of the Royal Society B: Biological Sciences. 278 (1711): 1548–1555. doi:10.1098/rspb.2010.1932. ISSN 0962-8452. PMC 3081750. PMID 21047861.
  20. ↑ Flower, Tom P.; Gribble, Matthew (2012-02-01). "Kleptoparasitism by attacks versus false alarm calls in fork-tailed drongos". Animal Behaviour. 83 (2): 403–410. doi:10.1016/j.anbehav.2011.11.009. ISSN 0003-3472. S2CID 53252968.
  21. 1 2 Flower, Tom P.; Child, Matthew F.; Ridley, Amanda R. (January 2013). Boots, Mike (ed.). "The ecological economics of kleptoparasitism: pay‐offs from self‐foraging versus kleptoparasitism". Journal of Animal Ecology. 82 (1): 245–255. doi:10.1111/j.1365-2656.2012.02026.x. ISSN 0021-8790. PMID 22943364.
  22. ↑ Child, Matthew F.; Flower, Tom P.; Ridley, Amanda R. (2012-10-01). "Investigating a link between bill morphology, foraging ecology and kleptoparasitic behaviour in the fork-tailed drongo". Animal Behaviour. 84 (4): 1013–1022. doi:10.1016/j.anbehav.2012.07.027. ISSN 0003-3472. S2CID 53176133.
  23. 1 2 3 Baigrie, Bruce D.; Thompson, Alex M.; Flower, Tom P. (2014-09-22). "Interspecific signalling between mutualists: food-thieving drongos use a cooperative sentinel call to manipulate foraging partners". Proceedings of the Royal Society B: Biological Sciences. 281 (1791): 20141232. doi:10.1098/rspb.2014.1232. ISSN 0962-8452. PMC 4132685. PMID 25080343.
  24. ↑ Yong, Ed (1 May 2014). "The Bird That Cries Wolf Changes Its Lies". National geographic. Archived from the original on May 2, 2014. Retrieved 2 May 2014.
  25. ↑ Flower, T. P. (2014). "Deception by Flexible Alarm Mimicry in an African Bird". Science. 344 (6183): 513–516. Bibcode:2014Sci...344..513F. doi:10.1126/science.1249723. PMID 24786078. S2CID 3005286.(subscription required)
  26. ↑ Flower, Tom (May 2015). "Dual parasitism of Fork-tailed Drongos by African and Jacobin Cuckoos". Ostrich. 86 (1–2): 189–191. doi:10.2989/00306525.2015.1029032. S2CID 84740346.
  27. ↑ Cracking the great cuckoo cover-up, University of Cambridge

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