Dicrurus macrocercus

Dicrurus macrocercus, commonly known as the black drongo, is a medium sized passerine bird native to much of southern Asia and parts of Indonesia. The species was introduced to Rota, Northern Mariana Islands, from Taiwan by the Japanese in the mid-1930s as a form of biological crop pest control. From Rota the species apparently self-colonized the nearby island of Guam. The black drongo has been implicated as a predator and held at least partially responsible for the decline of one of the IUCN’s Critically Endangered red-listed avian species on Rota, and has been observed as a source of frequent harassment to another. However, these assertions are supported by anecdotal evidence and no data indicate that drongos have a significant negative effect, or have played a significant role, in the decline of any bird species on Guam or Rota.

The native range of the black drongo includes Afghanistan, India and Sri Lanka, to Southeast Asia, southern and eastern China, Taiwan, Malaysia, Java and Bali.

The black drongo prefers open country including cultivation, roadsides, scrub, open areas around villages, and suburbs of towns and cities. The species also occurs in open broken forest and lightly wooded savannah and is often associated with cattle grazing. In Rota, the species was significantly more common in open habitats; about five times more common when compared to its abundance in closed habitats (Amar et al., 2008). It breeds mostly in lowlands but does occur up to 2000 m in warmer summer months. Black drongos build neat cup nests of grass and natural fibres, which they place in trees. The species tends to nest in close proximity to agricultural lands and electrical power lines in southern India (Ali et al., 2010).

The black drongo has a positive effect upon agriculture by feeding upon insect species that are considered serious crop pests (Chandy, 2003; Asokan, 2009).

Genetics

D. macrocercus forms a superspecies with (or, is a sister species of) Dicrurus adsimilis, the Fork-tailed Drongo, of sub-Saharan Africa (Pasquet et al., 2007). Five other species (D. fuscipennis, D. modestus, D. waldenii, D. forficatus and D. aldabranus) were once thought to be part of the same superspecies. Recent morphological and genetic data, however, indicated that the differentiation was considered too great to validate such a relationship (Pasquet et al., 2007).

Reproductive Biology

Breeding is reported to occur from February-August for the black drongo in India and central Asia and from April-August in Southeast Asia (Grimmett et al., 1999; Robson, 2000; Ali et al., 2010). The species constructs a medium sized, thin bottomed, cup-shaped nest that is placed in the forks of tree branches. Ali et al. (2010) reported nests placed between heights of 5.5 m and 12.5 m above the ground in southern India. Nests are typically constructed of dried fibres, grass, and twigs. Clutch sizes range from 2-5 eggs (Robson, 2000; Ali et al., 2010). Eggs can be white to pinkish-cream in colour and spotted or blotched with black or brown. Incubation, in which both parents participate, generally occurs with the laying of the first egg; the remainder of the eggs are laid at approximately 24 hour intervals thereafter. Eggs hatch between day 13 and 16 after being laid and young fledge between day 20 and 22 after hatching.
  
Activity Patterns

Black drongos are incomplete migrants, in that birds from the northern range of the species’ population overlap those in the southern portion of its range in winter. Northern and upper elevation populations migrate in autumn, wintering at lower elevations and latitudes as far south as central India in the west and Malaysia and Sumatra in the east. On their wintering grounds black drongos occur in tropical savannah, grassland, and agricultural areas (Decandido et al., 2004). Observations in southern Thailand indicate that migration begins in late September, peaks by late October, and mostly ends by early November (Decandido et al., 2004). Migrants tend to be most active daily between 08.00 h and 10.00 h and again between 17.00 h and 18.00 h (Decandido et al., 2004).
 
Nutrition

The black drongo is primarily insectivorous and typically forages from exposed perches in open areas, from where it frequently makes sallies at prey in mid-air or on the ground. It often hunts insects at dusk and where insects are attracted at night to artificial lights (Sharma, 1991; P. Radley, Commonwealth of the Northern Mariana Islands Division of Fish and Wildlife, Saipan, personal observation, 2007-2011). Insects most often consumed in agricultural areas in India include beetles, wasps, moths and butterflies, locusts and grasshoppers (Asokan et al., 2009). Black drongos have been recorded taking and eating small birds on Guam including Rufous Fantails (Rhipidura rufifrons), Mariana Swiftlets (Aerodramus bartschi), Eurasian Tree Sparrows (Passer montanus), and Rota White-eyes (Zosterops rotensis) on Rota (Engbring et al., 1986; US Fish and Wildlife Service, 2007). The species has also been observed taking small fish and aquatic insects at the surface of small ponds (Serrao, 1971; P. Radley, Commonwealth of the Northern Mariana Islands Division of Fish and Wildlife, Saipan, personal observation, 2007-2011).
 
Associations

Veena and Lokesha (1993) suggested the existence of a commensal association between black drongos and two myna species in India, the Common Myna (Acridotherus tristis) and Jungle Myna (Acridotherus fuscus). Both mynas forage in pure and mixed flocks in southern India. Drongos were found to benefit individually by associating with large foraging flocks of these species, which tend to flush flying insects while foraging for ground dwelling arthropods and grains (Veena and Lokesha, 1993).

Environmental Requirements

The range of the black drongo is tropical to subtropical, extending mostly north of the equator between 45 degrees north latitude and 8 degrees south latitude. The species prefers more open countryside than other drongo species, including areas of cultivation, grasslands and savannas, open scrub and broken forest, and urban and residential areas, up to 1500-2000 m in elevation in the summer. It breeds mostly in lowland areas.

There are no published data pertaining to predators or natural enemies of the black drongo within its native range. However, given their similar choice of habitat and the drongo’s foraging activities at or shortly after dark, Barn Owls (Tyto alba) could opportunistically prey upon them (Sharma, 1991; P. Radley, Commonwealth of the Northern Mariana Islands Division of Fish and Wildlife, Saipan, personal observation, 2007-2011). Brown tree snakes have been documented killing black drongos on Guam but the effect of the snake upon drongo populations on the island is unknown (Savidge, 1988). De Mello (1935) identified and described a species of Haemoproteus blood parasite for the black drongo (H. dicruri) in India but its clinical or physiological effects upon the species are unknown. However, the genus of the parasite is known to be host specific (Savage and Greiner, 2005).

Environmental

• Biological control

General

• Botanical garden/zoo
• Pet/aquarium trade

The black drongo is discerned from the ashy drongo (Dicrurus leucophaeus) by its shiny blue-black throat and breast, which merge into black on the remainder of the underparts. It is separated from the white-bellied drongo (Dicrurus caerulescens) by its black belly, flanks, and undertail-coverts. The black drongo could be confused with the crow-billed drongo (Dicrurus annectans), except that the latter has a shorter and less deeply forked tail and a heavier bill than the former. Additionally, crow-billed drongos occur in dense forest whereas black drongos reside in more open country. The black drongo could also be confused with an adult drongo cuckoo (Surniculus lugubris), the habitat for which can overlap that of the black drongo. However, the cuckoo has a fine, down-curved black bill, a slightly indented square ended tail, and a clean black belly and vent with white-barring on the under-tail coverts and on the underside of the shorter, outer-tail feathers.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Physical/Mechanical Control

In an effort to evaluate control measures necessary to reduce black drongo numbers on Rota, Craig (1999) reported shooting over 1000 drongos over eight mornings in 1991. He estimated that continued control efforts over at least 40 mornings would reduce the drongo population on the island by 80-90%. Both Lusk (1993) and Worthington and Taisacan (1994), however, found it difficult to control drongos on Rota using firearms. In the early 1990s the Commonwealth of the Northern Mariana Islands’ Division of Fish and Wildlife conducted a study to determine if the removal of black drongos on Rota would increase the abundance of white-eyes on the island (Lusk, 1993; Worthington and Taisacan, 1994). With repeated exposure to firearms drongos became wary of humans and fled when approached, well before being within shotgun range. No other efforts to control black drongos on Rota have been attempted.

US Fish and Wildlife Service (2005; 2007) states the need for research pertaining to the following on Rota: assessing the impact of black drongos upon both Mariana crows and Rota white-eyes; evaluation and development of black drongo control techniques; evaluation of the expected costs, benefits, and results of black drongo control; and testing the effectiveness of habitat restoration that benefits the crow and white-eye but not the black drongo. The US Fish and Wildlife Service (2005; 2007) suggests that such research is needed to determine if drongo control on Rota is warranted and if it should be a priority, based upon other conservation needs of both the Mariana crow and the Rota white-eye.

World: BirdLife International, Wellbrook Court, Girton Road, Cambridge, CB3 0NA, UK, http://www.birdlife.org

11/09/2012 Original text by:

Paul M. Radley, Commonwealth of the Northern Mariana Islands Division of Fish and Wildlife, Saipan, MP 96950