1. Introduction
Dispersion, migration and colonization are some of the fundamental features of living organisms. Therefore, changes in distribution and geographical ranges are natural, common and widespread, always and everywhere. Their intensities are related to environmental changes and to the dispersal and reproductive abilities of living organisms. However, humans can accelerate these changes on an unprecedented scale through high population growth and negative impacts on natural environment.
According to the ‘tens rule’ [1], only about 10% of introduced species develop a viable population. Out of these, c. 90% achieve a status of naturalized, established populations, and only c. 10% of them assume the status of invasive species. Those species pose serious ecological (e.g., disturbance of natural balance, dislocation of indigenous species), economic (e.g., agricultural pests) and social (e.g., human diseases) problems. In most regions of the world, the negative impact of invasive species constitutes the most important ecological problem, besides habitat destruction.
Most avian introductions were performed in the last three centuries, and most are associated with British colonization. Today, the major regions of avian introductions in the world include British major overseas settlements, i.e., Australia and New Zealand, Oceania (especially Hawaii), South Africa and the USA. The British deliberately tried to introduce exotic species, mainly for hunting purpose; hence, today, exotic birds are overrepresented by game birds [2]. The other motives for their introductions include pest control, aesthetic (bright coloration, pleasure songs), nostalgia and even conservation (e.g., Mandarin Duck Aix galericulata and Golden Pheasant Chrysolophus pictus) and religion (Buddhism and Taoism). However, most of the recent introductions are accidental and unintentional [3,4].
Avian invasion has been well-studied, but subsequently summarized for only some parts of the world, such as the USA [5,6,7,8,9], Great Britain and Europe [10,11,12,13] and Australia with New Zealand [14,15,16]. For most tropical parts of the world, no comprehensive reviews are available on a continental (zoogeographical regions) scale. The presented paper attempts to summarize our knowledge on avian introduction in one such region.
2. Materials and Methods
Since most avian introductions in Africa began in the middle of the 19th century with European colonization [2], the appropriate literature from 1900 onwards (with a special emphasis on the last 50 years) was reviewed for information on avian introduction south of the Sahara in Africa, including Madagascar and the following small islands and archipelagos: Cape Verde; São Tomé e Principe; Bioko and Annobón of Equatorial Guinea; the Mascarenes; Seychelles; Comoros; Mafia, Zanzibar and Pemba off the coast of Tanzania; and Socotra.
The Google Scholar bibliographic database (scholar.google.com) was searched for relevant literature. The following key words were used: introduced birds (or alien birds) + Africa (or particular African country and island). As key words, particular bird species (both common and scientific names) were also used + Africa (or particular African countries and islands), e.g., Passer domesticus + Africa; House Sparrow + Zambia; etc. Special websites dealing with introduced bird species were also consulted by direct search on the internet.
Species nomenclature and systematics follow Clements et al. [17].
Since definitions related to introductions differ between studies and authors, the following terms used in this article require clarification. The definitions are based mainly on the IUCN/WCU; IUCN 2015; and Bern Convention [18,19]. The following types of introduced species could be distinguished: Indigenous species (native, autochthonous): Species living within its natural range. Alien species (introduced, non-native, non-indigenous, foreign, exotic): species introduced by humanity intentionally or accidentally. Invasive alien species (invader): Species which has been introduced to areas it did not previously occupy, establishing a viable breeding population, spreading and becoming a pest affecting ecosystems and local biodiversity, economy and society (including human health). Non-invasive alien species: Introduced species with developed viable population of low dispersal abilities and not affecting adversely ecosystems, economy and society in conquered areas. Translocated species: Accidental escapee from aviary or enclosure; may reproduce in wild, but has not developed viable population. Post-invasive alien species (established, naturalized): Species introduced long time ago (before 1900), well established in wild, but without expansion tendencies. Cryptogenic species: Species of unknown origin (alien or indigenous), its expansion may be shaped by natural or anthropogenic factors.
The following types of introduction are recognized: Intentional introduction: The purposeful relocation of a species beyond its natural range. Unintentional introduction: The accidental relocation of a species beyond its natural range. Expansion: The continuous natural enlargement of a natural range by the acquisition of the adjacent areas or natural occupation of new habitats within the original range. Invasion (colonization): The natural spread into new areas accompanied by a rapid and often explosive exponential population growth and changes in the natural environment and human economy.
To characterize the populations of the introduced species, the following terms are used: Population stages: Not established, developing, viable, established (naturalized). Population growth (dynamic): Stable, increasing, declining, locally extinct. The types of invaded ecosystems can be grouped as follows: Natural ecosystems: Natural formations not altered and not disturbed by human, usually in the climax stage. Semi-natural: Natural formations modified/altered by humans, in successive or/and climax stages. Artificial ecosystems: Artificial formations created by human and not in a climax stage.
3. The Introduced Species
3.1. Invasive Alien Bird Species
Out of the 150 alien species introduced to sub-Saharan Africa in the last 200 years, 49 (32.7%) have developed viable populations (as shown in this study), but only 7 (4.6%) have become invasive [4,20,21,22,23], i.e., the House Sparrow Passer domesticus, Common Starling Sturnus vulgaris, Common Myna Acridotheres tristis, Red-whiskered Bulbul Pycnonotus jocosus, House Crow Corvus splendens, Rock Pigeon Columba livia var. domestica and Rose-ringed Parakeet Psittacula krameri (Table 1 and Table 2; Figure 1A–F).
3.1.1. House Sparrow
The original range of this species is the Middle East. In Africa, Passer domesticus indicus were introduced intentionally from India to Durban in the 1890s, and Passer domesticus domesticus from Great Britain to East London at the beginning of 20th century [49,50]. It had established a stable population in Gauteng only by the year 1950 [50]. By the 1980s, it had invaded most of southern Africa, including southern Democratic Republic of Congo (DRC) in the west and southern Tanzania in the east [50,51,52]. It is, however, still absent in the southern interior; for example, in 2013–2016, it was still absent in E Namibia and N Botswana (Table 3).
It has also invaded northern and eastern Madagascar and the surrounding islands. In Madagascar, it was first recorded in the mid-1980s in Toamasina [24,53].
In the 1890s, the House Sparrow was introduced to Zanzibar, from where it spread to central Tanzania [50]. In the 1950s, it was introduced from South Africa (probably by ship) to Mombasa [70], from where it spread (facilitated by trucks or trains) across Kenya along the Mombasa highway to Uganda [70]. In the 1970s, it was introduced from South Africa to Senegal, probably incidentally [29,37,52,71], and spread across Senegal and coastal Mauretania [50].
There has been a widespread and sharp decline of the House Sparrow in most European countries [72,73,74] and North America [75], but in Africa the situation is reversed. In most towns and cities in southern Africa it belongs to the most common bird species today, even in areas colonized quite recently in northern Namibia, i.e., in Opuwo, Outapi and Onguadiva, where it breeds in a density of 19–36 pairs per 10 ha (Table 3). It has been found to be especially abundant (comprising approximately half of the total breeding bird community) in impoverished rural parts (so called townships, locations) of towns and cities, e.g., Bloemfontein [53,55], Maseru [57], coastal towns in Namibia [60,61,76] and towns in the most northern parts of the country [68,69]. While the House Sparrow is most abundant in city centers (e.g., in Bloemfontein, 25 pairs per 10 ha [54]), it tends to be much less common in residential areas (e.g., in Bloemfontein, 2–3 pairs/10 ha [53]), especially well-timbered ones, where the indigenous sparrow species (i.e., Cape Sparrow Passer melanurus) are often more common (Table 3).
Today, the House Sparrow occurs in all continents except for Antarctica, and has also been introduced to islands, e.g., to the Lesser and Greater Antilles, Macaronesia, Madagascar, New Guinea, Japan and New Zealand [77].
3.1.2. Common Starling
The Common Starling’s original breeding range includes the Palearctic Region. In the late 1890s, Cecil Rhodes introduced 18 Common Starlings to Cape Town. Soon, they colonized the Cape Peninsula and spread northwards, crossing the Berg River in the year 1928. From there, they expanded eastwards, reaching East London by the year 1966, the Kei river by the year 1971 and Umtata in 1981 [38,78,79,80,81,82]. Today, they are widespread and common all over the Western and Eastern Cape provinces [39]).
The Common Starling was recorded for the first time in Durban 1973 [83]. By 1993, it was established along southern coast of the KwaZulu/Natal Province [25]. At the beginning of the 21st century, it was established in Gauteng Province. Its occupation of the dry interior was limited, but it had reached the Orange River by the year 1970 [23]. In the Free State Province, it was recorded for the first time on the southern border in 1986 [84]. The first breeding was confirmed in Bloemfontein in 1997/98 [85].
In Lesotho, the Common Starling was recorded for the first time in Maseru in 1988. In 1996–1998, 1–2 probably breeding pairs were present [57]. In Roma, the first breeding was recorded in 1991; ten years later there were at least 15–20 breeding pairs in this area, including 10 pairs per 82 ha on the NUL campus [58]. While in 1987–1997 only 1–2 pairs in two sites (Maseru, Roma) were known in Lesotho, 21–27 pairs in four sites (Maseru, Roma, St. Joseph and Masite) were recorded in 1998–2002 [86].
In Namibia, the Common Starling was first recorded in Oranjemund in 1970 [23]. At the beginning of 21st century, the Common Staring was recorded in southern Namibia (70 km south of Grünau, in Hohenfels and in Lüderitz on the coast), indicating further northward expansion [87].
As a result of its introduction, the Common Starling occurs in all continents of the world except Antarctica. Today, it is especially common in the USA, although a slight decline in numbers was recorded from 1966 to 2004 [7]. It is also common and widespread in SE Australia [30].
3.1.3. Indian Myna
The Common Myna’s original range includes SE Asia. In sub-Saharan Africa, the Common Myna Acridotheres tristis tristis (formerly regarded as A. t. tristoides) from Myanmar and Nepal was introduced to Durban in c. 1900. From there, it spread all over KwaZulu/Natal and NE Free State [83,84,85], where, for example, 3.5 pairs per 10 ha (with a dominance: 16.9%) were recorded in 1996 in Bethlehem town center (55 ha), also being a dominant species in the residential and industry areas in the town [56]. Spreading northwards along the coast, it reached Ponta Malongane in Mozambique in 1997 [88], whereas spreading southwards along the coast, it had reached Port Elizabeth and Cape Town by the beginning of the 21st century [88,89].
The Common Myna Acridotheres tristis tristis from India and Sri Lanka was introduced to Johannesburg in c. 1938 and Pretoria in 1955. In the latter city, it developed a viable population only in the 1980s. Although it was recorded as breeding in Kimberley, North West Province in the 1960s, it failed to develop viable population in the town [89].
In Lesotho, the Common Myna was first recorded in the mid-1990s in Maseru; in 1996–1998, 2–5 breeding pairs were recorded in the city [57], and 5–10 pairs were recorded in 1998–2002 [88]. The first record at Roma was made in 1999 [86]. In 1998–2002, it was also recorded in Morija and Leribe (two pairs in each town) [86].
In Botswana, the Common Myna was recorded for the first time in Nata near Jwaneng in 2012, and in Kasane on the Chobe River in 2014 [90]. In 2014, for the first time, it was also recorded in Victoria Falls on the Zimbabwe/Zambia border [91], about 100 km east of Kasane.
It invaded Namibia from the south and from the extreme north-east. In the south, it was recorded for the first time in Oranjamund in 2014 and in Rosh Pinah in 2017 [92]. In the north-east, it was first recorded in Katima Mulilo in 2016 (with the first breeding in the town in 2017) and in Ngoma in 2016 [93], c. 60 km west of Kasane. Therefore, the Common Myna has already crossed the Zambezi River and is most probably now spreading further north.
The Common Myna has also been introduced to Madagascar, Comoros, Mauritius, Mayotte, Seychelles, Reunion, Zambia and Zimbabwe. Beyond Africa, the Common Myna has been introduced to North America, the Middle East, Australia and New Zealand and numerous islands around the world.
3.1.4. House Crow
Naturally, the House Crow occurs in Iran, Afghanistan, Pakistan, India, Bangladesh, Burma, Nepal, Sri Lanka, Thailand and extremely south-western China [94,95,96].
It was introduced to sub-Saharan Africa for the first time in Zanzibar in the 1890s. From there, it spread along the coast (by ship) to Mombasa (1947), and from there along the railway to the Kenyan interior [97,98]. House Crows have also become well established in Mauritius.
In South Africa, the House Crow appeared on the Indian Ocean coast in the early 1970s. It was first recorded in Durban, where it has developed a sizable population. In the early 1990s, it also established a small population (several hundred individuals in the early 2000s) in Cape Town [21,98].
A control program in Durban has significantly reduced the numbers and range of the species. In 2019–2023, it occurred mainly in the Durban coastal area from the Blue Lagoon in Durban North to Isipingo to the south [99]. Subsequently, the main center of the population became Richard’s Bay, 200 km north of Durban. In Cape Town, where the population is markedly reduced, it now occurs mainly in the Khayelitsha area (sabap2.adu.org.za). Isolated individuals were recorded in East London on 15 June 2010 [100].
The House Crow was introduced unintentionally to various countries, often on ships as a ‘hitchhiker’, including Tanzania [101], and Socotra Island (Yemen). It was intentionally introduced to some countries to clean garbage and to control caterpillars and ticks on livestock [102]. In Zanzibar, crows were reported to be introduced in the 1890s, from where they spread to Kenya in 1947, especially along the coastal areas between Mombasa and Malindi, as well as hitchhiking on ships traveling from Asia to East Africa [97,103].
The House Crow has been introduced to the following countries: Benin (Cotonou, 2010), Djibouti, Egypt, Eritrea, Madagascar (Toamasina, 2014), Mauritius, Morocco, Mozambique (Maputo (1976), Pemba, Nacala, Quelimane, Beira and Matola), Namibia (Walvis Bay, 2011), Seychelles, Socotra Isl. (Hadibu, 1994: 1 individual; 1996: 3 individuals; 2003: 26 individuals), Somalia, South Africa, Sudan and Tanzania. A survey by Shimba [104] in Dar es Salaam city, Tanzania, estimated that there were 800,000 House Crows in the impoverished parts of the city.
As a result of their introduction, today the House Crow occurs in southern Asia, (from Turkey to Vietnam, in Japan and Australia), in the southern parts of the USA, in Central America, in South America (Chile) and in many countries in Europe [101,102,104,105,106,107,108,109,110].
3.1.5. Rock Pigeon
The Rock Pigeon occurs naturally in Mediterranean Europe, northern Africa and the Middle East, extending to south-east Asia [111,112]. As a result of its introduction, it occurs today in all continents except for Antarctica [113]. Outside its native range, it occurs in at least in 64 countries [111,112,113,114,115,116], and it is still expanding.
It was introduced to South Africa during the Angolo–Boer War (1899–1902) to enable efficient communication [117], and then became invasive. At present, it occurs all over southern Africa, reaching northern Angola in the west and northern Kenya in the east. It is, however, still absent in the DRC and in the East African Rift Valley [13,113]. In Namibia, it has reached high densities in towns such as Walvis Bay, Swakopmund and Katima Mulilo, but it is virtually absent in Hentjs Bay, Onguadiva and Tsumeb (Table 3). No geographical or ecological trends are apparent in this country.
In southern African cities/towns, population densities of the Rock Pigeon vary from 0 to 15 pairs/10 ha (Table 3). They may greatly vary even within the same city. For instance, the population density is 15.0 pars/10 ha in the city center of Bloemfontein, but in the neighboring residential suburbs, it is only 2.1 pairs per 10 ha. Similarly, in Bethlehem town center it is 7.3 pairs/10 ha, but none were recorded in the industrial areas (Table 3). In Lesotho, the Rock Pigeon is virtually absent in rural and urban areas, except for the capital, Maseru, where it is common in the city center [59].
3.1.6. Rose-Ringed Parakeet
The Rose-ringed Parakeet occurs naturally in the Sahel zone of Africa and SE Asia (Pakistan, India, Bangladesh Sri Lanka, Nepal and Myanmar). In South Africa, its expansion/invasion into five regions has been recorded, i.e., Cape Town, Steytlerville (NW of Porth Elizabeth), Shelley Beach (S of Port Shepstone), Bethal and Hazyview. It no longer occurs in five regions where it was recorded in 1987–1991, i.e., East London, Ladysmith (KwaZulu/Natal), St Lucia (KZN), Mkuze (KZN) and Leeudoringstad (North West Province) [118]. The species has developed a viable population only in Gauteng (mainly the Johannesburg and Pretoria areas), Durban and the Pietermaritzburg area.
It was first recorded as breeding in South Africa in the 1850s in Cape Town, but failed to develop a viable population [118]. It was seen there again in the 1980s, the 1990s and in 2010, but it still has not developed a viable population.
The Rose-ringed Parakeet was found to be breeding in Sodwana Bay in the late 1960s [119], in Mkuze Game Reserve in the early 1970s, in Mandini, Zululand, in July 1979 and in St Lucia in July 1982, but it failed to establish a viable population in all of these places. In Durban, it was introduced in the 1970s and soon began to expand [43,120]. In 2000, 700–1000 individuals were counted; in 2018–2019, 1783 ± 505 individuals/750 km2 [121] were counted, and it is still expanding.
In Gauteng, the first record of 5–8 individuals was made in 1985 in central Johannesburg. By mid-1990 the population increased to c. 200 individuals [118,119]; in 2013, at least 300–500 individuals in Johannesburg and at least 400 individuals in Pretoria were counted.
In recent years, it has been seen expanding across South Africa and Mauritius [42,120]. In November 2018, the Rose-ringed Parakeet was recorded in the Nhangaan Forest near Nhangau, Sofala Province, and in Maputo City in July 2021 and October 2021 [43].
Rose-ringed Parakeets have established viable breeding populations in many parts of the world. In Europe, they have developed viable populations in the UK, France, Germany, Belgium, the Netherlands, Spain, Portugal, Italy, Greece and Turkey. All the European populations numbered more than 85 000 individuals in 2016 [121]. It has also invaded northern Africa, the Middle East, Thailand, Indonesia and Japan. Recently, it was introduced to the New World, i.e., Florida, California, Venezuela and Hawaii [122,123].
3.1.7. Red-Whiskered Bulbul
The Red-whiskered Bulbul’s original range extends from Pakistan throughout SW China and India to Indochina. In Africa, it is well-established in Mauritius, where it was introduced intentionally in 1892. From there, it was introduced unintentionally to Reunion (1978) and Assumption Island in the Seychelles (1977) [124]. In 1987, there were c. 200 breeding pairs on Assumption Island, and several thousand individuals were there in 2014 [125]. In Mayotte, it was introduced in 1985, but unsuccessfully [126]. It has also been recorded in Madagascar, South Africa and Zimbabwe, although it has not developed viable populations in these countries.
As a result of its introduction, the Red-whiskered Bulbul now occurs in Japan, Indonesia, southern Malaysia, Singapore, Taiwan, Australia, Borneo, Hong Kong (China), the United Arab Emirates, Oman, Saudi Arabia, the USA (Hawaii), Juan de Nova Island, Spain, the Canary Islands and the Nicobar Islands [127,128].
3.2. Non-Invasive but Established Alien Bird Species
Most bird species which were introduced to sub-Saharan Africa and developed viable populations (n = 49 species) did not become invasive [4,19,20,21,22,128]. In most cases, the established populations are small with very restricted ranges. Most species have developed viable populations on small islands, mainly around Madagascar in the Indian Ocean (Table 1). On these small oceanic islands, some species may pose a threat to the indigenous fauna, becoming locally harmful and therefore invasive.
The Chaffinch is an exception in this regard. At the end of the 19th century, a flock was released in Cape Town, which developed a small population of 1500–2000 individuals by the beginning of 21st century in and around the city, in pine plantations between Tokai and Rondebosch and around Fish Hoek and Noordhoek [129]. Similar situations may exist for the Masked Lovebird, introduced to Dar es Salaam and Nairobi, and the Nyasa Lovebird, introduced to Lundazi, Zambia.
The Budgerigar is also a species of special interest in this group. From 1947, c. 50 individuals were recorded throughout the years in Umbogintwini, KwaZulu/Natal, but today its status is unknown. Apparently, it was established in the city of Swakopmund on the Atlantic Ocean in Namibia in 2001 [26], but it was not recorded there in 2017–2020 [63], nor in the neighboring towns of Walvis Bay [64] and Hentje’s Bay [62].
The Mallard is regarded as an invasive species in most areas where it was introduced. In Africa, although it was introduced a long time ago, it has not hitherto established viable populations. It exists in urban parks and gardens as a semi-domestic/feral poultry and does not adversely affect biodiversity nor the human economy [125]. The Graylag Goose, Muscovy Duck and American Black Duck are in similar situations.
3.3. Not-Established Alien Bird Species
Most species introduced to sub-Saharan Africa have failed to develop viable populations. This group includes 101 species. It is, however, important to point out that the real number might be much higher, as some introductions could have passed unrecorded, especially in countries beyond southern Africa. Excluded are here all species which could have been vagrants from their main range in other parts of Africa or short-lived aviary escapees, evidently not established even for one breeding season. For example, more than 30 parrot species have been observed in South Africa alone, most of them as escapees from cages [40].
Most of the introduced species were present for some time in the wild, but were probably not breeding and subsequently disappeared altogether. Some others did develop a viable population, but subsequently the population declined and became extinct in the introduced areas (e.g., Mute Swan). Some individuals may persist as feral individuals on farmyards.
Many ‘failed’ introductions in the Mascarenes were actually successful, often reaching invasive/pest status for decades (even a couple of centuries) before circumstances changed and they became locally extinct [32,33,44,130]. They were representatives of granivorous passerines (mostly from the family Estrildidae) and the Madagascar Lovebird Agapornis canus, Galliformes and game waterbirds. The Avadavat, Java Sparrow and Madagascar Lovebird went into local extinction when grain plants were no longer cultivated. In Mauritius, game birds and swamphens Porphyrio spp. suffered from the introduction of the Small Indian Mongoose Herpestes javanicus and also from the introduction the Cape Canary Serinus canicollis.
Among the interesting introductions is that of the Rook. In the late 1890s, as many as 200 individuals were released near Cape Town, but they failed to establish a breeding population [25]. The Blackbird was also released in Cape Town at the same time, and it even bred there for several years, but it finally became extinct by the year 1923 [25]. Similarly, the Song Thrush, released at the same place and time, developed a viable breeding population but subsequently declined and became extinct by the year 1947 [25].
4. The General Characteristics of the Avian Introductions in Sub-Saharan Africa
4.1. Species Representativeness
At present, 212 bird species have been successfully introduced from around the world. Out of this total, only c. 10% affect biodiversity adversely through predation (1%), competition with native species (3%) and other effects (5%) [131]. Worldwide, 64% of established introduced mammal species become invasive, while this proportion is only 34% for birds [132]. In the USA, 97 alien species developed ‘self-sustaining populations’ [7]; in Australia, out of 242 avian species introduced, 77 (32%) developed viable populations [15].
In sub-Saharan Africa, at least 146 bird species have been introduced, but only 49 of them (33.6%) have developed viable populations and only 7 (4.8%) became invasive (Table 1 and Table 3). According to Dyer et al. [128], 218 bird species were introduced to Africa. This number is certainly an underestimation, as there are a number of doubtful and inaccurate records on this list. For many species, no information on the place and year of their introduction is given; some records include de facto introductions or reintroductions of indigenous species to their native ranges; and some others may represent records of vagrant birds from other parts of Africa or ephemeral escapees from aviaries. In a similar way, the number of introduced species (n = 192) compiled by Downs and Hart seems to be an overestimation [4].
Most avian introductions in sub-Saharan Africa took place in Southern Africa (mainly the Cape Town, Durban and Johannesburg areas), in Madagascar and the surrounding islands (mostly Mauritius, Reunion and Seychelles) and on the coasts of Tanzania and Kenya (including the Pemba, Zanzibar and Mafia islands).
Over the last 200 years, two introduction peaks occurred in sub-Saharan Africa: the first at the end of the 19th century and the second at the end of the 20th and the beginning of the 21st century (Figure 2). The former resulted from the activity of the former British Acclimatization Society, which promoted introductions of alien species at the end of the 19th century in South Africa and other British colonies in Africa and beyond, for both utilitarian (hunting) and ‘aesthetic’ reasons (‘enrichment’ of local flora and fauna).
In the latter period, the peak was a result of increased commerce, international contact and interests of bird-lovers in keeping ornamental birds in aviaries and cages.
Worldwide, Psittacidae (131 species) and Anatidae (92 species) are the most speciose groups of invasive bird species [128]. Other families with high numbers of invasive species include Phasianidae, Passeridae, Fringillidae and Columbidae [15]. In sub-Saharan Africa, the most specious groups were parrots (Psittaciformes), comprising 33.6% (Psittacidae: 13.7%; Psittaculidae: 15.1%); Anatidae: 12.3%; Phasianidae: 11.0%; and Passeriformes: 30.1% (Estrildidae: 6.2%; Ploceidae: 5.5%; the most speciose passerine families) (Table 4).
Most introduced species in sub-Saharan Africa which have developed viable populations originate from Afrotropical, Oriental and Palearctic regions (altogether 78%), with only 2% being from the New World. The proportions among the introduced species which have not developed viable populations are quite different: 29% are from the New World, while 60% are from the Afrotropical, Oriental and Palearctic regions (Figure 3).
4.2. Factors Affecting Successful Introduction
There are several factors that determine the effective establishment of introduced species, i.e., environmental and landscape-level changes, food resources, climate (House Sparrow, Rock Pigeon, possibly Common Starling and Common Myna), ecological and physiological characteristics (e.g., behavior, breeding ecology, diet composition, juvenile development, migratory status, body size and genetic variability), and introduction circumstances (e.g., the time of release, the number of individuals released and the number of release events) [21,45,133,134,135,136,137].
Urbanization results in homogenization, with most introduced species present in urban areas [138]. This is because introduced species in urban areas exploit resources (food and nesting sites) better than native species [133,139]. In sub-Saharan Africa, all invasive species are strictly associated with urban environments, with some affinities to rural habitats.
4.3. Ecological Characteristic of Successful Species
There are several factors which determine the success of introduced bird species in sub-Saharan Africa.
(1). Whether the pioneer group is large enough to prevent stochastic extinction within the first few years. Escapees from aviaries, represented by various species of parrots, doves or finches, are usually single birds or a few individuals of the same sex. They cannot, therefore, persist in the wild for a long time [4,20].
(2). Being a commensal with humans and strongly associated with man-made structures (including impoundments), cultivations, lawns and gardens (Rock Pigeon, House Crow, House Sparrow). Their associations with humanity enable these species to exploit food resources (often human-processed food, like bread, meat, fruits, vegetables, etc.) and easily available nesting sites (e.g., holes in walls, under roofs, etc.) [4,20,28].
(3). Eurobionts (with a wide range in habitat tolerance), like the Common Starling or Rose-ringed Parakeet, are species which can easily adapt to changing environments and the various land forms managed by humans (e.g., residential, idustry and agricultural areas within urbanized landscapes) [4,26,140].
(4). Being a generalist feeder of invertebrates (e.g., pest species on monocultures), seeds and scraps of human-processed foods (Common Myna, House Sparrow, House Crow, Rock Pigeon, parrots) [4,29,126].
(5). Exhibiting communal roosting despite being single breeders (House Sparrow, Common Starling, Common Myna, Rock Pigeon, Rose-ringed Parakeet). These species usually breed in loose colonies, which may constitute an adaptation to an environment where food resources may vary spatially and temporaly [21,26,140].
(6). Group foraging (same species as above) [21,26,140].
(7). Climate tolerance. Although species such as the Rose-ringed Parakeet, Common Myna and pheasants originate from warmer parts of the world, they show high tolerances to low temparatures [4,21,29,39].
(8). An ‘r’-reproductive strategy (high clutch size and breeding success, few clutches per year). Species such as the Common Starling, House Sparrow, ducks and phaesants lay relatively large clutches, while doves lay 4–5 clutches per year [141].
(9). Being flexible in nest site selection, including man-made structures and alien trees and shrubs. For instance, the Common Starling or Rose-ringed Parakeet may nest in natural tree holes as well as in artificial nest-boxes or holes in walls [21,140].
(10). Being aggressive in the competition for food and nesting sites (Common Starling, House Saprrow, Common Myna) [26,126].
4.4. Factors Affecting Unsuccessful Introductions
In comparison to other parts of the world, most avian introductions in sub-Africa were unsuccessful. There are several factors which affected this.
(1). Having a too-low number of introduced individuals, which is often the case for escapees from aviaries, such as parrots and seed-eating finches [21].
(2). Species that do not benefit from urbanization or agriculture and are not strongly dependent on human activity. Most water birds and large terrestrial birds are in this category. They may have problems not only with the availability of suitable habitats but also with predators, especially cats, rats and dogs [3,4,20,21,141].
(3). A diet of mainly seeds/grain or insects. These may be scarce in human-modified environments [21,119,140].
(4). Competition from indigenous species. This may be especially acute in predators and insectivorous species [119,141,142].
(5). A preference for disturbed mesic habitats, but the avoidance of arid areas and natural vegetation, especially dense forests [3,4,20].
(6). Low breeding success due to egg and chick predation. This can be especially acute in ground-nesting birds due to the presence of dogs, cats, rats and mice [3,55,59].
(7). Predation on adults by a wide array of vertebrate predators and humans. This group may include birds belonging to the orders Anseriformes and Galliformes [3,4,20,21,141].
4.5. Introduction Pathways
Globalization facilitates and accelerates the rate of species invasions [143]. In sub-Saharan Africa, birds have been intentionally introduced into new areas for the following reasons: (1) acclimatization (acclimatization societies, which were popular in the 19th century in European colonies, introduced plants and animals into regions in which the fauna was considered deficient, e.g., many bird species in and around Cape Town); (2) biological control (control of insect populations, rodents, carcasses, etc.; e.g., Common Myna, House Crow, Red-whiskered Bulbul); (3) ornamental/aesthetic purposes (e.g., Chaffinch, Common Starling); (4) hunting purposes, as with game birds (most waterfowl and gallinaceous birds); and (5) the intentional release of captive pet or ornamental birds (most parrots and finches). However, many bird species were introduced unintentionally, often being escapees from aviaries (most ornamental birds) [140].
5. Management and Nature Conservation Implications
5.1. Impact Categories
Many of the introduced species cause apparently minimal or no damage, while others assume the status of persistent and destructive pests.
The introduction and naturalization of non-native species is one of the most important threats to global biodiversity. Seven types of impact on native ecosystems were evaluated: predation and competition [47,142,144,145]; hybridization [143]; the spread of disease and parasites [138,146]; and the chemical, physical, and structural impacts on ecosystems through grazing/herbivory/browsing. Most of these impacts are theoretical/potential/not evidenced [147].
5.1.1. Hybridization
The Mallard may hybridize with other ducks. The following species in Africa may be affected: the Yellow-billed Duck Anas undulata in South Africa, the African Black Duck Anas sparsa in South Africa and Meller’s Duck Anas melleri in Madagascar. The Mallard may pose a threat, especially in small oceanic islands [4].
5.1.2. Competition
The Common Starling competes for holes with other hole-nesting birds (e.g., Red-winged Starling Onychognathus morio, Little Swift Apus affinis, Olive Woodpecker Dendropicos griseocephalus). Usurping nests by contamination (as well as physical competition) is also a problem (e.g., native parrots use little, if any, bedding, whereas starlings will rapidly fill and contaminate tree hollows) [148,149,150]. The Rose-ringed Parakeet and the Common Starling, which breed prior to most other secondary cavity-nesting species, may reduce nesting site availability for bats and parrots.
Some endemic bird species at risk in the Seychelles may be negatively affected by alien bird species through competition for food. There is, however, a lack of any direct evidence of such competition. Alien mammals, such as cats and rats, play a much more important role in this regard. The group of endangered avian endemics includes the Seychelles Black Parrot Coracopsis barklyi, Seychelles Magpie Robin Copsychus sechellarum, Seychelles Paradise Flycatcher Terpsiphone corvina, Seychelles Fody Foudia sechellarum, Seychelles Scops Owl Otus insularis, Seychelles White-eye Zosterops modestus, Seychelles Swiftlet Aerodramus elaphrus, Seychelles Kestrel Falco araeus and Seychelles Blue Pigeon Alectroenas pulcherrimus. It should be mentioned that many of these species have been introduced to the neighboring islands in order to reduce the risk of their extinction [151]. Similar situation may exists on other small oceanic islands around Africa.
5.1.3. Predation
The Common Myna competes with the Seychelles Magpie Robin Copsychus sechellarum by occupying nest boxes and destroying eggs and chicks [152,153]. The Seychelles Magpie Robin is an endangered species. A similar situation was recorded concerning the critically endangered Seychelles Flycatcher Terpsiphone corvina [154], the vulnerable Seychelles White-eye Zosterops modestus and sea birds [155]. The House Crow destroys clutches or broods of other bird species, e.g., African Sacred Ibises Threskiornis aethiopicus, African Spoonbills Platalea alba and Black-headed Herons Ardea melanocephala [100]. The Red-whiskered Bulbul preys upon endangered native golden orb-weaving spiders (Nephila spp.) in Mauritius [156,157].
5.1.4. Disease Transmission
The House Sparrow is a reservoir of arthropod-borne viruses, such as the Western equine encephalitis virus, Eastern equine encephalitis virus, Buggy Creek virus, St Louis encephalitis virus and West Nile virus. Avian blood parasites were recorded in the following alien species: Foudia madagascariensis in Comoros, Mayotte, Seychelles, Mauritius [158] and Réunion [159]; Passer domesticus in South Africa [160,161] and Réunion [162]; Acridotheres tristis in South Africa [163] and Réunion [159]; and Geopelia striata, Leiothrix lutea, Estrilda astrild, Pycnonotus jocosus, and Ploceus cucullatus in Réunion [162].
The Common Starling is a reservoir of psittacosis Chlamydophila psittaci, bacteria (Escherichia coli, Salmonella spp., Campylobacter, Mycobacterium) and avian malaria Plasmodium relictum. Also, the Common Mynas is known as a reservoir of avian malaria, dermatitis, psittacosis, salmonellosis and arboviral infections [164]. The Rock Pigeon can be a reservoir of more than 60 different pathogens, including those recorded in the Common Starling. The Rose-ringed Parakeet is a carrier of some zoonotic diseases such as parrot fever Chlamydia psittaci and H9N2 Influenza A viruses [165]. The House Crow transmits Newcastle disease [162].
5.1.5. Parasitism
Virtually all birds have parasites which they transmit among themselves, and some may be transmitted to humans. The Rock Pigeon has an especially large burden of the following ectoparasites: bugs (e.g., Cimex lectularius), fleas (e.g., Ceratophyllus gallinae), flies (e.g., Fannia canicularis), mites (e.g., Dermanyssus gallinae) and ticks (e.g., Argas reflexus), that are known to infest humans [166].
5.1.6. Human–Wildlife Conflict
The Rock Pigeon, House Crow, House Sparrow, Common Starling and Common Myna cause damage to infrastructure, roof linings, buildings and monuments. The Common Starling forms large flocks in non-breeding seasons and is renowned for collisions with aircrafts. The House Crow attacks people to obtain food [167,168,169], and kills chickens on poultry farms (Dodoma, Tanzania; Ngongoda, Mirimi, 2024). The Rose-ringed Parakeet can cause severe noise disturbance, as it roosts in the thousands at night and has very loud vocalizations [121].
5.1.7. Agricultural Pests
The Common Starling is a notorious pest of fruits. It damages cherries and grapes especially often, but also damages figs, peaches, strawberries and blueberries. Also, the Common Myna may consume grapes, pears, strawberries, apricots, apples and other fruits. The Rose-ringed Parakeet is known to cause damage to vine grapes, almonds Prunus dulcis, Citrus spp., guavas Psidium guajava, mangos Mangifera indica and common sunflower Helianthus annuus heads [170,171]. The Rock Pigeon causes damage to maize, seeds, legumes (soybeans and chickpeas) and sunflower crops, while the House Crow damages fruits and crops such as cereal, maize and groundnuts [112,114,170,172,173].
5.1.8. Seed Dispersal
The Red-whiskered Bulbul disperses seeds of invasive plants, altering plant communities [157,174,175]). The Common Starling is known to disperse the invasive Western Coastal Wattle Acacia cyclops [176]. Psidium guajava, Persea americana, Mangifera indica and Eucalyptus sp. are dispersed also by frugivorous alien bird species, especially parrots [177].
5.2. Control Measures
Control measures to reduce detrimental alien bird populations include the following: prevention, early detection and rapid response, eradication and restoration. Some of the eradication methods include shooting, limiting food resources, clutch/brood destruction, trapping, using toxic substances, bioacoustics and sterilization [102,143,154,178,179]. The need for invasive species control, eradication methods used, etc., can vary depending on the species.
Feral and domestic cats are the main predators of the House Crow and Common Myna. The Peregrine Falcon Falco peregrinus is an efficient predator of the Rock Pigeon, while Accipiter raptors may efficiently control communally roosting birds, such as the House Sparrow, Common Starling, Common Myna or parrots. Some species, for example, the Common Starling, can be controlled using sonic devices.
Physical and chemical methods have been used to control Rock Pigeons, including shooting, poisoning, contraceptives, nest destruction and a reduction in food availability. Its eradication from small islands is feasible and achievable by trapping, nest destruction, shooting, poisoning and mist-netting [153].
Some examples of successful eradications are as follows: (1). The Common Myna on North Island, Seychelles (>200 ha; estimated populations of myna: c. 750–1000 individuals), 4641 individuals were killed [153,180,181]; Assumption Island (11.1 km2), Seychelles, 2004, 5270 individuals were killed [182]; Fregate Island (219 ha), Seychelles, 2010–2011, 745 individuals were killed [153]; Socotra [183]. (2). The House Sparrow on Round Island (219 ha), Mauritius. A total of 320 individuals were killed in 2008–2009 but it was not totally eradicated [184]. (3). The Madagascar Fody on Assumption Island, Seychelles. Over 3200 individuals were eliminated, with the last bird shot in January 2015 [185]. (4). The House Crow on Socotra Island. Between 2002 and 2008, the number of adults was successfully controlled by clutch/brood destruction. In April 2009, two professional snipers shot all the adults. A total of 242 young House Crows were collected and killed [169,186]. House Crows in Mauritius were poisoned with starlicide [186], while α-chloralose was applied as a means of narcosis that immobilized the crows and facilitated their capture [187]. (5). Red-whiskered Bulbul in Mayotte were eradicated in the 1990s [30]. On Assumption Island (Seychelles), 5279 birds were eliminted in 2012–2014 [185,188]; on the Mascarene Islands, pesticides and bird lime were used to kill the mynas (these untargeted chemicals also destroy indigenous birds) [189]; in Réunion, in addition to trapping, management practices were also used to mitigate human–wildife conflict to protect agricultural crops [48]. (6). The rose-ringed Parakeet in Mahé (155 km2), Seychelles. A total of 548 birds were shot from 2013 to 2017 by a team of professional hunters [141].
6. Conclusions
There are 1810 resident (breeding) bird species in sub-Saharan Africa [190]. This review lists an additional 150 bird species introduced to this region, 49 (32.7%) of which have developed viable breeding populations, but only 7 (4.7%) of which have become invasive species (Passer domesticus, Sturnus vulgaris, Acridotheres tristis, Corvus splendens, Columba livia var. domestica, Psittacula krameri and Pycnonotus jocosus). In comparison with other zoogeographical regions of the world, the proportion of introduced, and especially invasive, species appears to be relatively low. Since the invasive bird species are strongly associated with human-modified environments (urbanized or rural landscapes), their negative effects on biodiversity are under control. Only in small oceanic islands do the invasive species threaten the existence of numerous indigenous endemic species.
No new data were created or analyzed in this study. Data sharing is not applicable to this article.
I would like to express my thanks to Anthony S. Cheke for providing some information on introduced birds in the Mascarenes.
The author declares no conflicts of interest.
Footnotes
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.
Figure 1 Distributions of invasive bird species in sub-Saharan Africa: (A) House Sparrow, (B) Common Starling, (C) Common Myna, (D) House Crow, (E) Rock Pigeon, (F) Rose-ringed Parakeet.
Figure 2 Known years of successful (n = 51) and unsuccessful introductions (n = 54) of birds to sub-Saharan Africa.
Figure 3 Original zoogeographical regions of bird species introduced to sub-Saharan Africa.
Bird species introduced and established in sub-Saharan Africa.
| Scientific Species Name | Common Species Name | Family | Original Range | Expanded Range in Africa | Impact |
|---|---|---|---|---|---|
| Acridotheres tristis | Common Myna | Sturnidae | SE Asia | South Africa (Durban, 1888; Gauteng, Mpuma-langa, KwaZulu/Natal, Free State), Lesotho, Madagascar | high |
| Columba livia | Rock Dove | Columbidae | Southern Palearctic | South Africa, 1850; all over sub-Saharan Africa; Madagascar | high |
| Passer domesticus | House Sparrow | Passeridae | India | South Africa: Durban, 1893; confined to KwaZulu/Natal until 1950s. S and E Africa, Sahel zone, Senegal, Ivory Coast, Ghana, Madagascar | high |
| Sturnus vulgaris | Common Starling | Sturnidae | Europe | South Africa: Cape Town, 1897; Western Cape, 1950s; Eastern Cape, 1960s; KwaZulu/Natal, 1970s | high |
| Corvus splendens | House Crow | Corvidae | SE Asia | Zanzibar, 1890s; Kenya, 1947; Durban, 1972; Cape Town, 1979; Socotra, 1994. Established: SA, Tanzania, Kenya, Socotra | high |
| Psittacula krameri | Rose-ringed Parakeet | Psittaculidae | W Africa, SE Asia | SA: Cape Town: 1860; Durban: 1970s; Gauteng. Socotra, Mauritius, Zanzibar, Kenya, Cape Verde, Seychelles: 1970s | high |
| Pycnonotus jocosus | Red-whisk-ered Bulbul | Pycnonotidae | SE Asia | Established in Mauritius: 1892; Réunion: 1972; Seychelles: 1977. Present in Madagacar, South Africa, Zimbabwe | high |
| Alectoris chukar | Chukar Partridge | Phasianidae | Eurasia | South Africa: Robben Island, 1964 | medium |
| Gallus gallus | Red Junglefowl | Phasianidae | Orient | South Africa: KwaZulu/Natal, Mpumalanga (Gravellote); Réunion; Mayotte | medium |
| Numida meleagris | Helmeted Guineafowl | Numidae | Africa | Cape Verde, Comoros, Madagascar | medium |
| Anas platyrhynchos | Mallard | Anatidae | Holarctic | South Africa: 1940s; Gauteng: 1980s; Western Cape. Madagascar, Reunion, Mauritius | medium |
| Ardea ibis | Western Cattle-Egret | Ardeidae | Africa, Asia | Seychelles and possibly Rodrigues Island | medium |
| Geopelia placida | Peaceful Dove | Columbidae | Australia | Madagascar, Mauritius, Seychelles, Réunion, | medium |
| Geopelia striata | Zebra Dove | Columbidae | Australia | Seychelles: ‘hundreds of thousands of individuals’; Madagascar | medium |
| Agapornis canus | Madagascar Lovebird | Psittaculidae | Madagascar | Rodrigues, Réunion, Comoros, Seychelles; unsuccessful to Mauritius, Zanzibar, Mafia Islands, South Africa | medium |
| Agapornis fischeri | Fischer’s Lovebird | Psittaculidae | East Africa | Tanga (Tanzania); Southern Kenya; Cape St. Francis, 2014 | medium |
| Agapornis lilianae | Nyasa Lovebird | Psittaculidae | East Africa | Possibly introduced successfully to Zambia (Lundazi), Namibia and South Africa (Pretoria, 2013) | medium |
| Agapornis personatus | Masked Lovebird | Psittaculidae | East Africa | Dar es Salaam, Tanzania; Nairobi, Kenya | medium |
| Agapornis roseicollis | Rosy-faced Lovebird | Psittaculidae | SW Africa | South Africa: Johannesburg, c. 1984, successful; Modimolle, 1993; Cape Town, 2008; Durban, 2008 | medium |
| Tyto alba | Western Barn Owl | Tytonidae | Global | Seychelles: 1949; introduced to controls rats, preys on endagered Fairy Tern nests on small islands | medium |
| Foudia mada-gascariensis | Madagascar Fody | Ploceidae | Madagascar | Successful: Seychelles (Amirantes), Mauritius, Réunion, Rodrigues and possibly Comoros and Glorioso Islands | medium |
| Quelea quelea | Red-billed Quelea | Ploceidae | Africa | Successfully introduced to Réunion | medium |
| Estrilda astrild | Common Waxbill | Estrildidae | Africa | Successful: Mauritius, Rodrigues, Amirantes, Seychelles, Réunion, Cape Verde, São Tomé; unsuccessful: Madagascar | medium |
| Coturnix coturnix | Common Quail | Phasianidae | Palearctic | Successful: Réunion; unsuccessful: Seychelles, Mauritius, Comores | low |
| Synoicus chinensis | King Quail | Phasianidae | Orient, Australia | Mauritius, Kenya | low |
| Francolinus pintadeanus | Chinese Francolin | Phasianidae | China | Successfully introduced to Mauritius and possibly to Madagascar and Seychelles; unsuccessful: Réunion | low |
| Pavo cristatus | Common Peacock | Phasianidae | SE Asia | South Africa: Robben Island, 1968; Cape Town; Bloemfontein | low |
| Aix galericulata | Mandarin Duck | Anatidae | Palearctic | South Africa: Johannesburg, 1980, as breeding | low |
| Aix sponsa | Wood Duck | Anatidae | Nearctic | South Africa: Durban, 1880, as feral | low |
| Turnix nigricollis | Madagascar Buttonquail | Turnicidae | Madagascar | Glorioso Islands and Réunion; unsuccessfully introduced to Mauritius | low |
| Nesoenas picturatus | Malagasy Turtle-dove | Columbidae | Madagascar | Possibly successfully introduced: Mauritius and Réunion (perhaps native); | low |
| Spilopelia chinensis | Spotted Dove | Columbidae | Orient | Mauritius | low |
| Streptopelia decaocto | Collared Dove | Columbidae | Pelearctic | Successful: Cape Verde; unsuccessful: South Africa, Cape Town area | low |
| Melopsittacus undulatus | Budgerigar | Psittacidae | Australia | South Africa: KwaZulu/Natal, 1958; Pretoria, 1987; Melville, 1995; Swakopmund, 2001; Johannesburg, 2013 | low |
| Psittacus erithacus | Grey Parrot | Psittaculidae | Central Africa | South Africa: Pietermaritzburg, 2013 | low |
| Nymphicus hollandicus | Cockatiel | Cacatuidae | Australia | South Africa (Western Cape, Gauteng) | low |
| Amandava amandava | Red Avadavat | Estrildidae | Orient | Successful: Réunion, Mayotte; unsuccessful: South Africa (Rosherville), Mauritius | low |
| Lonchura punctulata | Scaly-breasted Munia | Estrildidae | Orient | Successful: Mauritius, Réunion; unsuccessful: Seychelles | low |
| Padda oryzivora | Java Sparrow | Estrildidae | Orient | Successful: South Africa: Port Alfred; Tanzania: Zanzibar; unsuccessful: Mauritius, Comoros, Seychelles | low |
| Uraeginthus angolensis | Blue-breasted Cordon-bleu | Estrildidae | Africa | Introduced possibly successfully to Zanzibar and São Tome e Principe | low |
| Passer hispaniolensis | Spanish Sparrow | Passeridae | Southern Palearctic | Cape Verde | low |
| Ploceus cucullatus | Village Weaver | Ploceidae | Africa | Successful: Mauritius, probably Réunion, possibly colonized or introduced to São Tomé; unsuccessful: Cape Verde | low |
| Ploceus melanocephalus | Black-headed Weaver | Ploceidae | Africa | Possibly introduced successfully to São Tomé | low |
| Fringilla coelebs | Common Chaffinch | Fringillidae | Palearctic | Cape Town: 1890s; Cape Peninsula | low |
| Carduelis carduelis | Goldfinch | Fringillidae | Palearctic | Successful: Cape Verde. Unsuccessful: Cape Town, 1891; Réunion | low |
| Crithagra mozambica | Yellow-fron-ted Canary | Fringillidae | Africa | Reunion, Mauritius, Rodrigues, São Tome e Principe | low |
| Serinus canicollis | Cape Canary | Fringillidae | Africa | Réunion; unsuccessful: Mauritius | low |
Data from: [
Bird species that were introduced/translocated/escaped from captivity in sub-Saharan Africa but did not establish a viable population, or those that established one but are now regarded as extinct or on the brink of extinction (denoted with ‘+’).
| Species Scientific Name | Species Common Name | Family | Origin | Range After Introduction |
|---|---|---|---|---|
| Tauraco violacea | Violet Turaco | Musophagidae | Sahel | Johannesburg, 1994–1995 + |
| Agapornis personatus | Yellow-collared Lovebird | Psittaculidae | Afrotropic | SA, 2011–2023; Kenya |
| Agapornis pullarius | Red-headed Lovebird | Psittaculidae | Afrotropic | Mayotte |
| Agapornis nigrigenis | Black-cheeked Lovebird | Psittaculidae | Afrotropic | SA: Pretoria, 2005 |
| Poicephalus cryptoxanthus | Brown-headed Parrot | Psittacidae | Afrotropic | SA: Johannesburg, 1977 |
| Poicephalus fuscicollis | Gray-headed Parrot | Psittacidae | Afrotropic | SA: Johannesburg, 2009 |
| Poicephalus gulielmi | Red-fronted Parrot | Psittacidae | Afrotropic | SA, 2011–2023 |
| Poicephalus meyeri | Meyer’s Parrot | Psittacidae | Afrotropic | SA: Johannesburg, 1981 |
| Poicephalus rueppellii | Ruppell’s Parrot | Psittacidae | Afrotropic | SA: Pretoria, 2007 and 2013 |
| Poicephalus rufiventris | Red-bellied Parrot | Psittacidae | Afrotropic | SA, 2011–2023 |
| Poicephalus senegalus | Senegal Parrot | Psittacidae | Afrotropic | SA, 2011–2023; Liberia |
| Streptopelia capicola | Ring-necked Dove | Columbidae | Afrotropic | Mayotte |
| Turtur tympanistria | Tambourine Dove | Columbidae | Afrotropic | Mayotte, Comoros |
| Coracias cyanogaster | Blue-bellied Roller | Coracidae | Sahel | SA: NW Province, 2003 |
| Melanocorypha bimaculata | Bimaculated Lark | Alaudidae | NE Africa | Namibia: Swakompund, 1930 |
| Corvus albus | Pied Crow | Corvidae | Afrotropic | Mauritius, Mayotte |
| Lamprotornis iris | Emerald Starling | Sturnidae | W Africa | SA: Midrand, 1993 |
| Lamprotornis superbus | Superb Starling | Sturnidae | E Africa | SA: Durban, 1993 and 1998 |
| Ploceus capensis | Cape Weaver | Ploceidae | Afrotropic | Mauritius |
| Ploceus intermedius | Lesser Masked Weaver | Ploceidae | Afrotropic | Socotra |
| Ploceus nigerrimus | Vieillot’s Black Weaver | Ploceidae | W, E Africa | SA: Durban, 2001–2002 + |
| Spermestes cucullata | Bronze Mannikin | Estrildidae | Afrotropic | Mayotte |
| Uraeginthus bengalus | Red-cheeked Cordon-blue | Estrildidae | Sahel | Unsuccessful: Cape Verde + |
| Vidua macroura | Pin-tailed Whydah | Viduidae | Afrotropic | Unsuccessful: Mayotte + |
| Vidua paradisaea | Eastern Paradise Whydah | Viduidae | Afrotropic | São Tome e Principe |
| Anas melleri | Meller’s Duck | Anatidae | Madagascar | Reunion, mid-18th century +?; Mauritius |
| Margaroperdix madagarensis | Madagascar Partridge | Phasianidae | Madagascar | Mauritius, Reunion + |
| Coracopsis vasa | Greater Vasa Parrot | Psittaculidae | Madagascar | Unsuccessful: Reunion + |
| Foudia seychellarum | Seychelles Fody | Ploceidae | Seychelles | Seychelles: Amirante Isl. + |
| Gallinula comeri | Gough Moorhen | Rallidae | Gough Is. | SA: Cape Town, 1893 + |
| Gallinula nesiotis | Tristan Moorhen | Rallidae | Tristan de Cunha, Gough Island | SA: Cape Town 1893 + |
| Gallus sonneratii | Gray Junglefowl | Phasianidae | Oriental | SA |
| Lophura nycthemera | Silver Pheasant | Phasianidae | Oriental | SA: Ceres (Western Cape) |
| Ortygornis pondicerianus | Gray Francolin | Phasianidae | Oriental | Reunion |
| Perdicula asiatica | Jungle Bush-quail | Phasianidae | Oriental | Reunion |
| Cairina moschata | Muscovy Duck | Anatidae | Oriental | SA, Mayotte |
| Psittacula cyanocephala | Plum-headed Parakeet | Psittaculidae | Oriental | SA: Pretoria, c.1979 +; Pietermaritzburg, 1899 + |
| Psittacula eupatria | Alexandrine Parakeet | Psittaculidae | Oriental | Socotra |
| Cacatua sulphurea | Yellow-crested Cockatoo | Cacatuidae | Oriental | SA: Pretoria, 1976–1983 |
| Dendrocitta vagabunda | Rufous Treepie | Corvidae | Oriental | Cape Town, 1997 |
| Gracula religiosa | Common Hill Myna | Sturnidae | Oriental | Reunion |
| Leiothrix argentauris | Silver-eared Mesia | Leiotrichidae | Oriental | SA: Gauteng, 2002 |
| Leiothrix lutea | Red-billed Mesia | Leiotrichidae | Oriental | Reunion |
| Lonchura striata | White-rumped Munia | Estrildidae | Oriental | Reunion + |
| Cygnus atratus | Black Swan | Anatidae | Australian | SA: Humansdorp, 1926 |
| Geopelia cuneata | Diamont Dove | Columbidae | Australian | Mauritius (before 1768), Seychelles, Réunion, SA |
| Eolophus roseicapilla | Galah Cockatoo | Cacatuidae | Australian | SA, 2011–2023 |
| Eclectus roratus | Moluccan Eclectus | Psittaculidae | Moluccas | SA, 2011–2023 |
| Neophema pulchella | Turquoise Parrot | Psittaculidae | Australian | SA, 2011–2023 |
| Neopsephotus bourkii | Bourke’s Parrot | Psittaculidae | Australian | SA, 2011–2023 |
| Platycercus elegans | Crimson Rosella | Psittaculidae | Australian | SA, 2011–2023 |
| Platycercus eximius | Eastern Rosella | Psittaculidae | Australian | SA, 2011–2023 |
| Cyanoramphus novaezelandiae | Red-crowned Parakeet | Psittacidae | New Zealand | SA, 2011–2023 |
| Taeniopygia guttata | Zebra Finch | Estrildidae | Australian | SA: Gauteng, 1984, E Cape |
| Alectoris melanocephala | Arabian Partridge | Phasianidae | Arabia | Eritrea + |
| Phasianus colchicus | Common Pheasant | Phasianidae | Palearctic | SA: Western Cape (4 sites), 1900–1950 +; Réunion |
| Anser anser | Feral Graylag Goose | Anatidae | Palearctic | SA, 18th century |
| Aythya ferina | Common Pochard | Anatidae | Pelearctic | SA: Cape Peninsula |
| Aythya fuligula | Tufted Duck | Anatidae | Pelearctic | SA: Pietermaritzburg |
| Aythya nyroca | Ferrugineus Duck | Anatidae | Palearctic | SA: Gauteng, 1994 |
| Cygnus olor | Mute Swan | Anatidae | Palearctic | SA: Eastern Cape, 1918; Western Cape. Nyanga (Zimbabwe) |
| Netta rufina | Red-crested Pochard | Anatidae | Palearctic | Zimbabwe, 1986; SA: 1996, 2003 |
| Tadorna tadorna | Common Shelduck | Anatidae | Pelearctic | SA: 5 records: 1974, 1985, 1989, 1990, 1995 |
| Falco columbarius | Merlin | Falconidae | Palearctic | SA: KwaZulu/Natal, 1991 |
| Turdus merula | Blackbird | Turdidae | Pelearctic | SA, late 1890s, 1923 + |
| Turdus philomelos | Song Thrush | Turdidae | Pelearctic | SA, late 1890s, 1947 + |
| Luscinia megarhynchos | Nightingale | Turdidae | Pelearctic | SA, late 1890s + |
| Corvus frugilegus | Rook | Corvidae | Pelearctic | SA, late 1890s + |
| Passer montanus | Eurasian Tree Sparrow | Passeridae | Palearctic | Réunion |
| Pastor roseus | Rosy Starling | Sturnidae | Palearctic | Mauritius |
| Colinus virginianus | Northern Bobwhite | Phasianidae | Nearctic | Harare, Drakensberg |
| Meleagris gallopavo | Wild Turkey | Phasianidae | Nearctic | Unsuccessful: Mauritius + |
| Callipepla californica | California Quail | Odontophoridae | Nearctic | SA + |
| Aix sponsa | Wood Duck | Anatidae | Nearctic | SA: 4 sites, 1997, 1999, 2001, 2002 |
| Anas rubripes | American Black Duck | Anatidae | Nearctic | SA: Durban, 1975 |
| Oxyura jamaicensis | Ruddy Duck | Anatidae | Nearctic | SA |
| Callonetta leucophrys | Ringed Teal | Anatidae | Neotropic | SA: Vaalkop Dam, 1985 |
| Dendrocygna autumnalis | Black-bellied White-faced Duck | Anatidae | Neotropic | SA: Vaalkop Dam, 1997 |
| Eudocimus ruber | Scarlet Ibis | Threskiornithidae | Neotropic | SA: KwaZulu/Natal, 2000–2001 |
| Columbina inca | Inca Dove | Columbidae | Neotropic | SA: Eastern Cape, 1992 |
| Fulica americana | American Coot | Rallidae | Nearctic | SA: Durban, 1891 + |
| Amazona aestiva | Blue-fronted Amazon | Psittacidae | Neotropic | SA: Pinetown, 1989 |
| Amazona amazonica | Orange-winged Amazon | Psittacidae | Neotropic | SA, 2011–2023 |
| Amazona oratrix | Yellow-headed Amazon | Psittacidae | Neotropic | SA, 2011–2023 |
| Ara ararauna | Blue-and-yellow Macaw | Psittacidae | Neotropic | SA, 2011–2023 |
| Aratinga jandaya | Jandaya Conure | Psittacidae | Neotropic | SA: KwaZulu/Natal, c. 2005 |
| Aratinga nenday | Black-hooded Conure | Psittacidae | Neotropic | SA: Eastern Cape, before 1983; Johannesburg, 2001 |
| Aratinga solstitialis | Sun Conure | Psittacidae | Neotropic | SA, 2011–2023 |
| Aratinga weddellii | Dusky-headed Conure | Psittacidae | Neotropic | SA: KwaZulu/Natal, c. 2005 |
| Cyanoliseus patagonus | Burrowing Parrot | Psittacidae | Neotropic | SA: Midrand, 1999 |
| Eupsittula pertinax | Brown-throated Parakeet | Psittacidae | Neotropic | SA: Eastern Cape, before 1983 |
| Forpus passerinus | Green-rumped Parrotlet | Psittacidae | Neotropic | SA: Durban, 1870s + |
| Myiopsitta monachus | Monk Parakeet | Psittacidae | Neotropic | SA? |
| Pyrrhura molinae | Green-cheeked Conure | Psittacidae | Neotropic | SA, 2011–2023 |
| Paroaria coronata | Red-crested Cardinal | Thraupidae | Neotropic | SA: Western Cape, 1958 |
| Paroaria dominicana | Red-cowled Cardinal | Thraupidae | Neotropic | SA: Durban, 1960s |
Data from: [
Population densities (pairs/10 ha) and dominance of House Sparrow and Rock Pigeon in selected southern African towns. Explanations: D—density (pairs per 10 ha); %D—dominance (percentage of breeding pairs of species in relation to total number of all breeding pairs of all species). For sample size, ‘p.’ denotes number of breeding pairs of all species.
| Town | Size of Study Plot | p. of All Species | Year | H. Sparrow | Rock Pigeon | Source | ||
|---|---|---|---|---|---|---|---|---|
| D | %D | D | %D | |||||
| Bloemfontein, whole, SA | 5100 ha | 1997 | 2.3 | 4.4 | 0.8 | 1.5 | [ | |
| Bloemfontein, city center, SA | 123 ha | 1994 | 25.0 | 13.7 | 15.0 | 8.2 | [ | |
| Bloemfontein, resid. area, SA | 55 ha | 1993 | 3.4 | 3.2 | 2.1 | 1.9 | [ | |
| Bethlehem, city center, SA | 55 ha | 1996 | 10.9 | 16.9 | 7.3 | 11.3 | [ | |
| Bethlehem, residen. area, SA | 326 p. | 1996 | - | 0.9 | - | 0.6 | [ | |
| Bethlehem, industr. area, SA | 89 p. | 1996 | - | 41.6 | - | 0.0 | [ | |
| Maseru, Lesotho | 1631 p. | 1996–1999 | - | 3.3 | - | 1.3 | [ | |
| Roma, Lesotho | 82 ha | 1998–2001 | 0.4 | 0.7 | 0.0 | 0.0 | [ | |
| Semonkong, Lesotho | 460 p. | 1996–2002 | - | 8.5 | - | 0.0 | [ | |
| Thaba Tseka, Lesotho | 657 p. | 1996–2002 | - | 5.5 | - | 0.0 | [ | |
| Mokhotlong, Lesotho | 339 p. | 1996–2002 | - | 13.6 | - | 0.0 | [ | |
| Morija, Lesotho | 295 p. | 1996–2002 | - | 0.0 | - | 0.0 | [ | |
| Lesotho, 14 large villages | 533 p. | 1996–2002 | - | 5.2 | - | 0.0 | [ | |
| Windhoek, Central Namibia | 5139 p. | 2011–2014 | - | 5.3 | - | 4.1 | [ | |
| Hentjes Bay, W Namibia | 345 ha | 2016/2017 | 4.1 | 16.6 | 0.0 | 0.0 | [ | |
| Swakopmund, W Namibia | 415 ha | 2016/2017 | 1.7 | 7.1 | 3.2 | 13.8 | [ | |
| Walvis Bay, W Namibia | 260 ha | 2016/2017 | 4.4 | 9.4 | 8.6 | 18.7 | [ | |
| Opuwo, NW Namibia | 85 p. | 2020 | - | 57.6 | - | 9.0 | [ | |
| Namibia, 3 towns, semidesert | 59 p. | 2018–2020 | - | 13.6 | - | 13.6 | [ | |
| Outapi, N Namibia | 130 ha | 2017 | 19.2 | 48.4 | 1.5 | 3.9 | [ | |
| Ongwediva, N Namibia | 100 ha | 2018 | 36.4 | 48.8 | 0.0 | 0.0 | [ | |
| Tsumeb, NE Namibia | 190 p. | 2017 | - | 4.7 | - | 0.0 | [ | |
| Grootfontein, NE Namibia | 276 p. | 2014 | - | 1.8 | - | 2.5 | [ | |
| Rundu, NE Namibia | 90 p. | 2015 | - | 0.0 | - | 8.9 | [ | |
| Katima Mulilo, NE Namibia | 214 ha | 2014/2015 | 0.0 | 0.0 | 3.6 | 10.1 | [ | |
| Katima Mulilo, NE Namibia | 177 ha | 2013 | 0.0 | 0.0 | 2.3 | 0.4 | [ | |
| Katima Mulilo, NE Namibia | 85 ha | 2015 | 0.0 | 0.0 | 7.4 | 15.8 | [ | |
| Kasane, NE Botswana | 160 ha | 2014/2016 | 0.0 | 0.0 | 0.0 | 0.0 | [ | |
Systematic positions of bird species introduced to sub-Saharan Africa.
| Taxonomic Rank | Established | Not Established | Total | |||
|---|---|---|---|---|---|---|
| n | % | n | % | N | % | |
| Galliformes | 8 | 16.3 | 11 | 11.3 | 19 | 13.0 |
| Phasianidae | 7 | 14.3 | 9 | 9.3 | 16 | 11.0 |
| Odontophoridae | 0 | 0.0 | 1 | 1.0 | 1 | 0.7 |
| Numidae | 1 | 2.0 | 0 | 0.0 | 1 | 0.7 |
| Anseriformes | 4 | 8.2 | 14 | 14.4 | 18 | 12.3 |
| Anatidae | 4 | 8.2 | 14 | 14.4 | 18 | 12.3 |
| Ciconiiformes | 1 | 2.0 | 1 | 1.0 | 2 | 1.4 |
| Threskiornitidae | 0 | 0.0 | 1 | 1.0 | 1 | 0.7 |
| Ardeidae | 1 | 2.0 | 0 | 0.0 | 1 | 0.7 |
| Falconiformes | 0 | 0.0 | 1 | 1.0 | 1 | 0.7 |
| Falconidae | 0 | 0.0 | 1 | 1.0 | 1 | 0.7 |
| Gruiformes | 1 | 2.0 | 3 | 3.1 | 4 | 2.7 |
| Rallidae | 0 | 0.0 | 3 | 3.1 | 3 | 2.1 |
| Turnicidae | 1 | 2.0 | 0 | 0.0 | 1 | 0.7 |
| Columbiformes | 6 | 12.2 | 5 | 5.2 | 11 | 7.5 |
| Columbidae | 6 | 12.2 | 4 | 4.1 | 10 | 6.8 |
| Musophagiformes | 0 | 0.0 | 10 | 10.3 | 1 | 0.7 |
| Musophagidae | 0 | 0.0 | 1 | 1.0 | 1 | 0.7 |
| Coraciformes | 0 | 0.0 | 1 | 1.0 | 1 | 0.7 |
| Coracidae | 1 | 2.0 | 1 | 1.0 | 2 | 8.2 |
| Psittaciformes | 9 | 18.4 | 39 | 40.2 | 49 | 33.6 |
| Psittacidae | 1 | 2.0 | 19 | 19.6 | 20 | 13.7 |
| Psittaculidae | 7 | 14.3 | 15 | 15.5 | 22 | 15.1 |
| Cacatuidae | 1 | 2.0 | 2 | 2.1 | 3 | 2.1 |
| Psittrichasidae | 0 | 0.0 | 1 | 1.0 | 1 | 0.7 |
| Strigiformes | 1 | 2.0 | 0 | 0.0 | 1 | 0.7 |
| Tytonidae | 1 | 2.0 | 0 | 0.0 | 1 | 0.7 |
| Passeriformes | 20 | 40.8 | 25 | 25.8 | 44 | 30.1 |
| Alaudidae | 0 | 0.0 | 1 | 1.0 | 1 | 0.7 |
| Corvidae | 0 | 0.0 | 3 | 3.1 | 3 | 2.1 |
| Pycnonotidae | 1 | 2.0 | 0 | 0.0 | 1 | 0.7 |
| Turdidae | 0 | 0.0 | 3 | 3.1 | 3 | 2.1 |
| Sturnidae | 2 | 4.1 | 3 | 3.1 | 5 | 3.4 |
| Passeridae | 2 | 4.1 | 1 | 1.0 | 3 | 2.1 |
| Ploceidae | 4 | 8.2 | 4 | 4.1 | 8 | 5.5 |
| Viduidae | 0 | 0.0 | 2 | 2.1 | 2 | 1.4 |
| Estrildidae | 5 | 10.2 | 4 | 4.1 | 9 | 6.2 |
| Fringillidae | 4 | 8.2 | 0 | 0.0 | 4 | 2.7 |
| Leiothrichidae | 0 | 0.0 | 2 | 2.1 | 2 | 1.4 |
| Thraupidae | 0 | 0.0 | 2 | 2.1 | 2 | 1.4 |
| Total | 49 | 100.0 | 97 | 100.0 | 146 | 100.0 |
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