Corvus splendens (bird)

Ecology Distribution Management Info Impact Info References and Links Contacts

General Impact Introduced populations of house crows often present major problems to humans and native wildlife (Feare and Mungroo 1990). In addition to the ecological damage, the house crow also inflicted economic damage by predating chicks and eggs (making free-ranging poultry impossible) and eating crops such as maize (Zea mays) and sorghum (Sorghum vulgare) (Archer 2001, in Lim et al. 2003). The house crow is a nuisance to people and presents a real threat to the tourist amenities and industry in some regions. C. splendens is an intestinal carrier of at least eight human enteric diseases (Ash 1984a, in Ryall 1992). 15 % of crows carried serotypes of Salmonella, 8 % Plesiomonas, 4 % enteropathic Escherichia coli, 3 % Shigella and 3 % Aeromonas hydrophila. Please see detailed impacts for more details on the impacts of the house crow.          Location Specific Impacts: Hong Kong   Reduction in native biodiversity: Potentially the greatest ecological concern is related to the recent increase in house crow numbers. Currently, the population is restricted to a limited geographical area and is wholly urban. It is unlikely to be significantly interacting with native wildlife, with most roosts being located in city parks (P.J. Leader pers. com., in Leven and Corlett 2004). These parks are of limited importance for wildlife, though of considerable amenity value. The house crow population is geographically close to the only egretry in the Hong Kong harbour area (Wong 2002, in Leven and Corlett 2004). This is of concern in view of the house crow’s known adverse effects on ardeid colonies elsewhere in the world (Ryall 1992, in Leven and Corlett 2004). Israel   Reduction in native biodiversity: In Israel two bird species (the common myna and the house crow) have been spotted harassing, preying on, or competing with local species of reptiles and birds. Kenya   Competition: The following bird species have been observed being harassed by C. splendens in the Mombasa area: cattle egret (Bulbulcus ibis), woolly-necked stork (Ciconia episcopus), hadada (Bostrychia hagedash), Eurasian marsh harrier (Circus aeruginosus), black-breasted snake eagle (Circaetus pectoralis), little sparrowhawk (Accipiter minullus), Walhberg’s eagle (Aquila wahlbergi), lizard buzzard (Kaupifalco monogrammicus), pale chanting goshawk (Melierax canorus), African fish eagle (Haliaeetus vocifer), black kite (Milvus migrans), black-shouldered kite (Elanus caeruleus), curlew sandpiper (Calidris ferruginea), little stint (Calidris minuta), Sooty gull (Larus hemprichii), black and white cuckoo (Clamator jacobinus), pied kingfisher (Ceryle rudis), mangrove kingfisher (Halcyon senegaloides), Eurasian bee-eater (Merops apiaster), lilac-breasted roller (Coracias caudate), golden oriole (Oriolus oriolus) and the pied crow (Corvus albus). Economic/Livelihoods: In Kenya the damage done by Corvus splendens is economically important in the case of maize, mangoes, pawpaws, poultry and goats. Livestock are threatened by the scavenging behaviour of house crows. In Kenya C. splendens kills large numbers of poultry, new- to attacks, particularly when crow attempt to steal their food. The house crow is also a crop-raider and frequently damages young maize cobs, as well as soft fruits like mangoes, pawpaws and bananas, thus rendering them useless for selling (Ryall 1992). Fruit and other crops are spoiled by house crows in Africa (eg: Kenya), India (Ali 1944, Ali et al. 1982), Aden, Yemen (Ash 1984a) and the Maldives (Ash 1984a) (cited in Ryall 1992).born lambs/goats and calves left unattended. Lesions on dairy cattle may be exacerbated by the birds, eventually leading to the death of the animal. Dogs and cats are often subjected to attacks, particularly in incidents when crows attempt to steal their food. House crows may also present an economic problem by thieving fish from fish farms, either directly from the surface of rearing ponds or from drying area as fish are being sun-dried. In at least one fish farm near Mombasa (Kenya) they are known to frequently grab fish from fish-rearing ponds (R. Waller, pers. comm., in Ryall 1992). Human nuisance: Corvus splendens are extremely noisy and frequently enter dwellings, hotels and restaurants where they steal food from plates and buffets, sometimes defaecating on tables and chairs. In Mombasa, Kenya, they are a serious nuisance in the coast hotels and numerous complaints have been received from tourists and tourist organizations. The authorities there consider them as adversely affecting the tourist industry. They also scatter refuse in public places, foul seats in parks and steal food from street vendors and market stalls. Reduction in native biodiversity: Corvus splendens has been observed preying on the following bird species in and near Mombasa: grey heron, black-headed heron, feral pigeon (Columba livia), yellow-collared lovebirds, speckled moosebird, scarlet-chested sunbird, grosbeak weaver, Zanzibar red bishop , golden palm weaver, black-headed weaver, house sparrow (Passer domesticus), red-cheeked cordon-bleu, bronze manikin. The most affected are the black-headed and golden palm weavers. Colonies of these birds in Mombasa have been displaced and are subject to constant nest-raiding in the breeding season. The spotted morning thrush and the black-backed puffback were once frequent in the gardens on Mombasa Island but declined drastically as the population of C. splendens increased. The native pied crow (Corvus albus) at one time roosted in large trees at Mombasa station gathering every evening in substantial numbers. C. splendens shared this roost in growing numbers until they finally ousted their larger but less aggressive cousins in the 1960s (R. McVicker, pers. comm., in Ryal 1992). C. albus and the black kite (Milvus migrans) were formerly common scavengers in Mombasa but since the proliferation of C. splendens they are only seen occasionally. Some non-avian species have also become prey, including bats, lizards and frogs. Crows are often seen noisily chasing fruit bats which are usually killed and eaten. This has resulted in the disappearance of epauletted fruit bat (Epomophorus wahlbergi) from many of the eaves and palms where it used to roost. Mombasa (Kenya)   Reduction in native biodiversity: The most dramatic effect linked to house crow presence in Mombasa has been the virtual elimination of small native birds such as weavers (Ploceidae) and sunbirds (Nectariniidae) (Ryall and Reid 1987, C.J.F., personal observations in 1985, in Feare and Mungroo 1990) and, locally, the displacement of native pied crows Corvus albus (Britton 1980, in Feare and Mungroo 1990). Malaysia   Agricultural: Potential crop pest (Yap and Sodhi 2004). Competition: Competes with native species (Yap and Sodhi 2004). Human nuisance: Communal roosts annoy residents (Yap and Sodhi 2004). Reduction in native biodiversity: Attacks small birds and eats their eggs (Yap and Sodhi 2004). Corvus splendens is well known as a nest-raider of ploceida and other native birds in its native India (Reid 1881, Ali 1956, Lamba 1976) as well as in much of its introduced range: Malaysia (D.R. Wells pers. comm.), the Seychelles (Ryall 1986), Zanzibar (Alexander 1985) and mainland Tanzania (N. Baker, pers. comm.) (cited in Ryall 1992). Mauritius   Disease transmission: It is reported that at least eight species of animal intestinal parasites are known to be harboured by the Indian house crow while disease-causing organisms can also be transmitted passively via their feet, bills and bodies (Archer Pers. Comm., in Puttoo and Archer 2003). These can be passed to humans by the fouling of water supplies and food sources (Ryall and Reid 1987, in Puttoo and Archer 2003). In Mauritius crows have been observed at market places, slaughter house, public gardens, coastal beaches and also known to visit reservoirs and available water points for bathing and drinking purposes. Human nuisance: The Indian house crow is an incessant cawer and is reported to steal food from market stalls and kitchens. It may also damage TV aerials and electrical lines and fouls buildings and public gardens and roadways (eg: Jardin de la Compagnie). Some incidents of crow attacks in Tombeau Bay and Pointe aux Sables have also been reported. Reduction in native biodiversity: This introduced avian species has no natural predators in Mauritius and this factor coupled with favourable environmental conditions has contributed to its successful colonisation. It has been reported that Indian crow has negative influence on the survival of other indigenous birds species. The effect of the house crow on the small populations of endemic birds and other animals on oceanic islands, such as the Seychelles and Mauritius, could be ecologically catastrophic. Most of the small birds in Mauritius have been introduced, the only common and widespread endemic being the Mascarene grey white-eye (Zosterops borbonicus) (Feare and Mungroo 1990). Surveys carried out in the field in selected areas showed complete absence of the Mauritian grey white eye (Zosterops mauritianus) where the Indian house crow exists in high densities, which confirmed possible predation of eggs and fledglings in their nests. It is unlikely that house crows, tied as they are to human proximity, will threaten the existing populations of the rarer endemic birds which are largely restricted to the small area of indigenous forest on the high ground of the south-west (Diamond 1987, in Feare and Mungroo 1990). However, if current conservation programmes are successful and some of the presently endangered birds, such as the pink pigeon (see Nesoenas mayeri in IUCN Red List of Threatened Species) and Mauritius kestrel (see Falco punctatus in IUCN Red List of Threatened Species), extended their ranges from forest into more disturbed habitats, the ranges of these birds may begin to overlap with that of the crows. In this case the crows could threaten the continued expansion of the endemics (Feare and Mungroo 1990). Qatar   Competition: House crows are suspected to be raiding domestic pigeon nests on Halul Island (Nation et al. 1997, in Ryall 2002). Saudi Arabia   Human nuisance: It is considered to be a pest in parts of Jeddah with reports of attacks on humans appearing in the local press. Seychelles   Economic/Livelihoods: House crows may also present an economic problem by thieving fish from fish farms, either directly from the surface of rearing ponds or from drying area as fish are being sun-dried (eg: in the Seychelles and the Maldives, Ryall 1986, Ash 1984a, in Ryal 1992). Reduction in native biodiversity: Corvus splendens is well known as a nest-raider of ploceida and other native birds in its native India (Reid 1881, Ali 1956, Lamba 1976) as well as in much of its introduced range: Malaysia (D.R. Wells pers. comm.), the Seychelles (Ryall 1986), Zanzibar (Alexander 1985) and mainland Tanzania (N. Baker, pers. comm.) (cited in Ryall 1992). Singapore   Human nuisance: The noise from house crow roosts, and the accumulated droppings, are a nuisance to residents who live nearby. When the crows gather to roost, they often perch on structures and buildings nearby, soiling them and sometimes damaging associated fixtures. During the breeding season, adult nesting crows occasionally attack passers-by (Soh et al. 2002). Reduction in native biodiversity: Although Lim & Gardner (1997, in Lim et al. 2003) speculated that the house crow may be out-competing and causing the decline of the native large-billed crow (Corvus macrorhynchos), it is equally likely that the latter’s decline is caused by a reduction in habitat (e.g. secondary forests, mangroves). Tanzania, United Republic of   Reduction in native biodiversity: Corvus splendens is well known as a nest-raider of ploceida and other native birds in its native India (Reid 1881, Ali 1956, Lamba 1976) as well as in much of its introduced range: Malaysia (D.R. Wells pers. comm.), the Seychelles (Ryall 1986), Zanzibar (Alexander 1985) and mainland Tanzania (N. Baker, pers. comm.) (cited in Ryall 1992). For example, the black kite (Milvus migrans) is being driven out of urban areas in Dar-es-Salaam, Tanzania, by the house crow (C. splendens). Zanzibar (Tanzania, United Republic of)   Reduction in native biodiversity: Corvus splendens is well known as a nest-raider of ploceida and other native birds in its native India (Reid 1881, Ali 1956, Lamba 1976) as well as in much of its introduced range: Malaysia (D.R. Wells pers. comm.), the Seychelles (Ryall 1986), Zanzibar (Alexander 1985) and mainland Tanzania (N. Baker, pers. comm.) (cited in Ryall 1992). For example the native pied crow (Corvus albus) has been displaced by C. splendens in Zanzibar (Pakenham 1979, in Ryall 1992). Yemen   Economic/Livelihoods: The house crow is a crop-raider and frequently damages young maize cobs, as well as soft fruits like mangoes, pawpaws and bananas, thus rendering them useless for selling (Ryall 1992). Fruit and other crops are spoiled by house crows in Africa (eg: Kenya), India (Ali 1944, Ali et al. 1982), Aden, Yemen (Ash 1984a) and the Maldives (Ash 1984a) (cited in Ryall 1992). In Aden, Yemen, Ash (1984a) reported that 2 – 3 % of calves and 10 – 15 % of newborn sheep and goats were killed by C. splendens in the absence of preventive action (cited in Ryall 1992). Dogs and cats are often subjected to attacks, particularly in incidents when crows attempt to steal their food. Aden (Yemen)   Disease transmission: House crows may be related to important public health problems. In one study different members of Enterobacteriaceae including Salmonella, and Shigella serotypes and Proteus strains as well as members of Vibrionaceae and Pseudomonads were isolated from a great proportion of crows. Some of them were found identical to the strains previously isolated from patients suffering from diarrhea in Aden. Giardia lamblia cysts and Hymenolepis nana ova were also recovered from crows. It was concluded that crows may participate in the spread of diarrheal diseases in Aden (al-Sallami 1991). Economic/Livelihoods: House crows have become a major pest in the Aden-Lahej-Abiyan region due to the extremely high density that the house crow population has reached in these areas. These populations have presumably been supported by the highly available refuse, drying fish and market gardens (al-Sallami 1991). Fouling: The house crow pollutes the environment by dropping their faecal material all over the city (al-Sallami 1991).