Blue Swallow Hirundo atrocaerulea


Justification of Red List Category
This intra-African migratory species is threatened by destruction and degradation of its grassland and wetland habitats on both its breeding grounds and its non-breeding grounds. The destruction of natural habitat has been found to have led to a rapid reduction of its already small population, which is projected to continue in the future unless immediate conservation action is taken across its entire distribution range. The species is therefore classified as Vulnerable.

Population justification
The total population has declined by an estimated 36–56% since the 1850s, and has been estimated at 1,006 pairs or 2,012 individuals (Evans and Bouwman 2010), and between 1,169 and 1,338 pairs (Evans et al. 2016). Estimated numbers of breeding pairs should be treated with caution, as when nests are surveyed they are assumed to indicate one breeding pair each, which may not be the case in this facultative cooperative breeder, and it has been observed that some nests are not used after construction (J. Wakelin in litt. 2007). It is conservatively placed in the band 1,000-2,499 mature individuals given the uncertainty over estimated numbers, and the maximum number of pairs is only just above this range. This equates to 1,500-3,749 individuals in total, rounded here to 1,500-4,000 individuals.

Trend justification
There is evidence that it has declined as a breeding species throughout its range (S. W. Evans in litt. 2007), owing to the widespread conversion and degradation of its grassland and wetland habitats. The rate of population decline is thought to be under 30% over ten years (S. W. Evans in litt. 2007), or possibly as loss as 8% over ten years (Evans et al. 2015).

Distribution and population

Hirundo atrocaerulea is an intra-African migrant that breeds in South Africa, west Swaziland, Zimbabwe, Malawi (F. Dowsett-Lemaire and R. J. Dowsett in litt. 1999, 2000, Holroyd and Quinn undated), north-east Zambia, south-western Tanzania (N. Baker in litt. 1999, D. Moyer in litt. 1999), west Mozambique, and south-east Democratic Republic of Congo (DRC) (Keith et al. 1992). It is a non-breeding visitor to north-east DRC, south Uganda (M. Carswell in litt. 1999) and west Kenya (Keith et al. 1992). 74% of the total breeding population occurs in Zimbabwe, Malawi and southern Tanzania. Uganda and Kenya host an estimated 73% of the non-breeding population (Evans and Bouwman 2010). It is uncommon to rare in Zambia and Zimbabwe and close to extinction in Swaziland and South Africa (Evans and Barnes 2000) where its population is estimated at around 100 pairs (Monadjem et al. 2006), though this could be as low as 40 pairs (McKechnie and Little 2012). The species range in South Africa and Swaziland is thought to have contracted by 74% (Evans and Bouwman 2010). It is reported that no active nests were located in Swaziland in 2006 (J. Wakelin in litt. 2007). There were thought to be 84 pairs in South Africa in 2005 (Anon. 2005b, M. McNamara in litt. 2006). The species was not recorded in Limpopo Province during national surveys in 2003 (Mattison 2004, Anon. 2005a) and 2004 (Anon. 2005a, Anon. 2005b), and it is not thought to have nested in the province during those seasons (Anon. 2005b). The total population has declined by an estimated 36–56% since the 1850s, and is now estimated at 1,006 pairs or 2,012 individuals (Evans and Bouwman 2010), or between 1,169 and 1,338 pairs (Evans et al. 2016).


This species breeds in montane grassland (Keith et al. 1992, Berruti et al. 1995, Holroyd and Quinn undated), preferring high rainfall, undulating areas such as mist belt grasslands of South Africa (Evans 2000). It favours grassland with interspersed with drainage lines in gullies or valleys, and also frequents wetland systems such as pans and small dams (Anon. 2005b). The species requires such wetlands among grassland patches for foraging (Anon. 2005b). In Swaziland, its breeding sites have been restricted to grasslands above 1,200 m, with most above 1,300 m (Monadjem et al. 2006). Prior to its northwards migration, it may congregate akin to Barn Swallow, Hirundo rustica, giving twittering calls (Meikle 2012). In its non-breeding range it favours open grassland, often with bushes and trees (Keith et al. 1992, Ndang'ang'a 2004, Ndang'ang'a 2007) and marshy areas (Ndang'ang'a 2007). Its nest is usually attached to the roof or side of a hole in the ground (relatively free of vegetation) (Turner and Rose 1989, Keith et al. 1992, Johnson 1996). Nest-sites in South Africa and Swaziland include underground sinkholes or disused aardvark Orycteropus afer burrows (Mattison 2003, Wakelin 2004, Monadjem et al. 2006), as well as artificial and artificially altered holes (Mattison 2003, Monadjem et al. 2006) such as old mining and prospecting shafts (Meikle 2010). Birds use the same nest-site for up to 30 years (Keith et al. 1992, S. L. Childes in litt. 1999, 2000), as long as the cavity remains stable (Wakelin 2004), although it is not known whether these are the same birds returning (J. Wakelin in litt. 2007). The nest consists of a cup of mud, mixed with fine grass and rootlets, and lined with feathers, and is repaired each year (Wakelin 2004). The species has been recorded breeding cooperatively in some parts of its range (facultative cooperative breeder) (Wakelin 2004, S. W. Evans in litt. 2007). However, it is not known whether helpers are related to the breeding pair (Wakelin 2004). Nesting occurs between October and March (Monadjem et al. 2006). A successful pair may produce two broods per breeding season (Wakelin 2004, Monadjem et al. 2006), with three clutches fledged from one nest in KwaZulu-Natal (J. Wakelin in litt. 2007). It lays two or three eggs, normally three; incubation lasts about 15 days and the chicks fledge after about 22 days (Wakelin 2004). The total number of active nests seems to be positively correlated with rainfall prior to breeding, probably through its influence on the abundance of insects, which the species feeds on (Monadjem et al. 2006). Blue swallow often forage in dense fog. They are well adapted to these conditions, having the most water repellent plumage of any terrestrial bird species (Rijke et al. 2000, Kylin et al. 2011).


Grassland in many parts of its range is being lost to afforestation (Keith et al. 1992, Wakelin 2004), intense human settlement, cultivation (especially sugarcane [Evans 2000]), intensive livestock-farming, intense grazing, intensive grass-burning (Nasirwa and Njoroge 1997), invasion by non-native trees and bracken (S. L. Childes in litt. 1999, 2000) and (potentially) small-scale mining (S. W. Evans verbally 1998). Grasslands are burnt annually or sometimes biannually to stimulate new growth for grazing; annual burning and grazing alters the composition of plant species and reduces their cover, accelerating soil erosion, reducing the organic content of soil and thus insect abundance and reducing the productivity and diversity of grasslands (S. W. Evans in litt. 2007, J. Wakelin in litt. 2007). The drainage of wetlands also threatens the species (Anon. 2005b). More than 60% of the South African Grassland Biome Habitat has already been irreversibly transformed (Evans 2000). Only 0.24% of montane grassland in KwaZulu-Natal is protected (Wakelin 2004). At five study sites in KwaZulu-Natal, 55% of the suitable grassland habitat was transformed between 1980 and 2000, and the number of active nests also halved (Wakelin 2004, M. McNamara in litt. 2006). At these sites, in addition to afforestation which doubled in area over the 20 year period and also accounted for half of the total land-use of the study area, grassland was also altered by the encroachment of woody vegetation, as a result of a lack of fuelwood harvesting by displaced communities and changes in fire regimes and timber plantation management (Wakelin 2004, J. Wakelin in litt. 2007). In Mpumalanga, 61% of suitable habitat in the North-eastern Mountain Sourveld has been transformed (M. McNamara in litt. 2006). Nesting attempts by the species in Mpumalanga and Limpopo Provinces (South Africa) were thought to be adversely affected by cold, dry conditions in October and November 2004 (Anon. 2005b), probably as a result of a low abundance of insects. In Swaziland, 42% of potentially suitable grassland above 1,300 m has been transformed or heavily degraded since the 1950s (Monadjem et al. 2006). Suitable breeding habitat in this country has been lost mostly to afforestation for exotic timber plantations, as well as urbanisation to a lesser extent (Monadjem et al. 2006). The Busia Grasslands (Kenya) have lost over 60% of their grassland cover since the mid-1990s (Ndang'ang'a 2007). They are surrounded by intensive agriculture, mainly maize and sugarcane (Ndang'ang'a 2004, Ndang'ang'a 2007), and are grazed by livestock (Ndang'ang'a 2007). The grasslands are severely and immediately threatened by fragmentation, agriculture and overgrazing (Ndang'ang'a 2004) from the large, rapidly increasing human population (Ndang'ang'a 2007) in adjacent settlements, some of which are highly populated (Ndang'ang'a 2004). Local people in Busia commonly trap swallows for food, and this may include H. atrocaerulea (Ndang'ang'a 2007, P. K. Ndang'ang'a in litt. 2007). The loss of grasslands outside the Ruma National Park (Kenya) is severe, with almost every available area cultivated, heavily grazed or settled (Ndang'ang'a 2007). The species's nest-site fidelity (Wakelin 2004) may increase its susceptibility to the affects of habitat transformation. Breeding birds are known to abandon their nests in reaction to human disturbance from excessive tourism (Mattison 2003) and land-owners (Wakelin 2004). At the Blue Swallow Natural Heritage Site (BSNHS), South Africa, nesting success has been reported to decline during years with increased fog (Evans and Bouwman 2000). Blue Swallows are well-adapted to flying in dense fog and have the most water repellent plumage of any terrestrial bird species (Rijke et al. 2000). Kylin et al. (2011) hypothesise that elevated concentrations of sulphonates in the fog, caused by a combination of increased air pollution from the Johannesburg area and volatile organic compounds (VOCs) released from exotic trees, may have increased the wettability of the blue swallow plumage and lowered nesting success.

Conservation actions

Conservation Actions Underway
CMS Appendix I and II. In 1986, an international working group was established for the conservation and recovery of the species throughout its range (Anon. 2005b). The group has helped to prevent afforestation of the species's grasslands and wetlands in five key areas, successfully lobbied for grasslands in eight areas to be rehabilitated, and succeeded in blocking prospecting and mining in two key areas in South Africa (M. McNamara per Anon. 2005b). A workshop was held in South Africa in June 2002, followed by the publication of an international action plan (Evans et al. 2002). A South African working group has been formed to coordinate and encourage conservation of the species (Evans 2000, Holroyd and Quinn undated). In Malawi, Nyika National Park and the Mulanje area are considered secure from agricultural encroachment in the long term, owing to the cold climate and poor soils (F. Dowsett-Lemaire in litt. 1997). In Zimbabwe, c.200 pairs breed within Nyanga National Park (S. L. Childes in litt. 1999, 2000), and less than 50 pairs breed in Chimanimani National Park (S. L. Childes in litt. 1999, 2000). The Ruma National Park is a stronghold for the species in Kenya (Ndang'ang'a 2007). The majority of the few known pairs in Swaziland breed in Malolotja Nature Reserve (Parker 1994, Monadjem et al. 2006), with two pairs in recent years on Sibebe Mountain, which has been the focus of a community-based conservation project (Monadjem et al. 2006). In Mpumalanga and KwaZulu-Natal, artificial nest cavities have been dug (Wakelin 2004, Anon. 2005b, S. W. Evans in litt. 2007) to encourage the species into previously unoccupied areas where there are no natural nest sites (Anon. 2005b), and some remain in use (Wakelin 2004). However, artificial nests are less warm than natural nests, and the possible impacts of this for breeding in this species are, as of yet, still uncertain (Wakelin et al. 2013). Of the 44 artificial nest sites created in KwaZulu-Natal, 18 have been used once or more, but 26 remain unused (Anon. 2005b). Research is underway in South Africa to investigate the minimum size of grassland required by breeding pairs through the use of radio-tracking and wing-marking studies (Wakelin 2004). The species's breeding success in South Africa is monitored anuually (Mattison 2003, S. W. Evans in litt. 2007). In South Africa, a national count (Mattison 2004, Arnott 2004, Anon. 2005a) and breeding survey in KwaZulu-Natal (Mattison 2003, Arnott 2004) and Mpumalanga (S. W. Evans in litt. 2007) are carried out annually in October-November. Environmental education programmes are ongoing in the regions of South Africa where the species breeds (M. McNamara in litt. 2006).

Conservation Actions Proposed
Identify key wintering sites and conserve them (L. Bennun in litt. 1999). Survey and monitor breeding population size and trend at less well-studied sites (M. Dyer in litt. 1999, S. L. Childes in litt. 1999, 2000). Control and remove non-native plants at breeding sites (S. L. Childes in litt. 1999, 2000). Assess effects of grassland fires on spread of non-native plants. Prevent further loss of grassland habitat in Kenya (Ndang'ang'a 2004). Survey the species's entire range in Swaziland to obtain data on its breeding population (Monadjem et al. 2006). In Swaziland, increase the area of protected grassland above 1,300 m (Monadjem et al. 2006). Consider the burning of grassland patches to prevent shrub and tree encroachment and encourage swarms of insects for the species to feed on (Ndang'ang'a 2007). Initiate a conservation strategy for the Busia Grasslands that can incorporate development (Ndang'ang'a 2007). Raise public awareness of the species's plight and importance of its habitat (M. McNamara in litt. 2006). Prevent any further significant loss of suitable habitat in South Africa (M. McNamara in litt. 2006). Reduce disturbance by tourists and land-owners. Study habitat use in its wintering range (S. W. Evans in litt. 2007). Determine the characteristics of drainage lines used or foraging (S. W. Evans in litt. 2007). Identify migration routes used between breeding and wintering grounds (S. W. Evans in litt. 2007). Study breeding biology in greater detail, including the effects of differences in conditions within natural and artificial nest holes (S. W. Evans in litt. 2007). Carry out surveys to obtain a population estimate for southern Tanzania (S. W. Evans in litt. 2007). Study the species's demography and longevity (S. W. Evans in litt. 2007). Study the genetics and taxonomy of the species (S. W. Evans in litt. 2007).


18-25 cm. Small swallow with very long outer tail feathers. Appears all-black, but in sunlight is deep, metallic blue. Female and juvenile have shorter outer tail feathers. Similar spp. Black Sawwing Psalidoprocne holomelas is matt black, not iridescent, with shorter, less deeply forked tail. Voice A chip or chip-chip contact call and musical bee-bee-bee-bee in nuptial flight display. Hints Easily located at higher elevations over grasslands on Nyika and Viphya Plateau (Malawi), in Vumba and Chimanimani areas (Zimbabwe), south-eastern Tanzania and over seasonally flooded grasslands in Sango Bay (Uganda).


Text account compilers
Ekstrom, J., Evans, M., Shutes, S., Starkey, M., Taylor, J., Allinson, T & Westrip, J.

Aspinwall, D., Baker, N., Bennun, L., Carswell, M., Childes, S., Dowsett, R., Dowsett-Lemaire, F., Dyer, M., Evans, S.W., Moyer, D., Ndang'ang'a, P. & Tarboton, W.

Recommended citation
BirdLife International (2021) Species factsheet: Hirundo atrocaerulea. Downloaded from on 21/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from on 21/10/2021.