Overview
The house crow (Corvus splendens), also known as the Indian, greynecked, Ceylon or Colombo crow, is a common bird of the crow family that is of Asian origin but now found in many parts of the world, where they arrived assisted by shipping. It is between the jackdaw and the carrion crow in size (40 cm in length) but is slimmer than either.
The forehead, crown, throat and upper breast are a richly glossed black, whilst the neck and breast are a lighter grey-brown in colour. The wings, tail and legs are black. There are regional variations in the thickness of the bill and the depth of colour in areas of the plumage.
Distribution and Habitat
The house crow has a widespread distribution in southern Asia, being native to Nepal, Bangladesh, India, Pakistan, Sri Lanka, Maldives and Laccadive Islands, southern Myanmar, south Thailand, and coastal southern Iran. It was introduced to East Africa around Zanzibar (about 1897) and Port Sudan.
A population between 200 and 400 birds has been present in Sham Shui Po, New Kowloon, Hong Kong. In Singapore, there was a density of 190 birds per square kilometer in 2001, with efforts to suppress the population in planning.
Urban Association
It is associated with human settlements throughout its range, from small villages to large cities. Due to a human population explosion in the areas it inhabits, this species has also proportionately multiplied. Being an omnivorous scavenger has enabled it to thrive in such circumstances.
Behaviour and Ecology
Diet
House crows feed largely on refuse around human habitations, small reptiles and mammals, and other animals such as insects and other small invertebrates, eggs, nestlings, grain and fruits. House crows have also been observed swooping down from the air and snatching baby squirrels. Most food is taken from the ground, but also from trees as opportunity arises. They are highly opportunistic birds and given their omnivorous diet, they can survive on nearly anything that is edible.
These birds can be seen near marketplaces and garbage dumps, foraging for scraps. They have also been observed to eat sand after feeding on carcasses.
Nesting
At least some trees in the local environment seem to be necessary for successful breeding although house crows occasionally nest on telephone towers. It lays 3–5 eggs in a typical stick nest, and occasionally there are several nests in the same tree. In South Asia they are parasitized by the Asian koel. Peak breeding in India as well as Peninsular Malaysia is from April to July. Large trees with big crowns are preferred for nesting.
Roosting
House crows roost communally near human habitations and often over busy streets. A study in Singapore found that the preferred roost sites were in well-lit areas with a lot of human activity, close to food sources and in tall trees with dense crowns that were separated from other trees. The roost sites were often enclosed by tall buildings.
Before flying into roost trees, crows make pre-roosting aggregations perched on TV antennas, roof tops, wayside trees, open fields, and feed or preen during this time.
Vocalizations
The voice is a harsh kaaw-kaaw. House crows are known for their distinctive calls and can be quite vocal, especially at dawn and dusk when gathering at roosting sites.
Invasive Species Status
The invasive potential for the species is great all over the tropics. This species can make use of resources with great flexibility and appears to be associated with humans, and no populations are known to exist independently of humans. Based on niche-modelling, it is estimated that it can also persist in some coastal areas in southern and northwestern Europe.
In 2016, house crow was added to the List of Invasive Alien Species of Union concern in the European Union. The breeding population of this species is reported from Netherlands, while individuals were seen in Belgium, Hungary, Poland and Spain.
Relationship to Humans
It is suspected that paramyxoviruses, such as PMV 1 that causes Newcastle disease, may be spread by Corvus splendens. Outbreaks of Newcastle disease in India were often preceded by mortality in crows. They have also been found to carry Cryptococcus neoformans, which can cause cryptococcosis in humans.
In some areas, house crows are viewed as pests due to their large numbers, noise, and aggressive behavior towards other birds. However, they also play a role in waste management by consuming garbage and carrion. The species' high intelligence and adaptability have made it a successful colonizer of urban environments across many regions.
Conservation Status
The house crow is listed as a species of Least Concern by the IUCN due to its large range and population. However, in regions where it is introduced, it is often subject to control measures due to its status as an invasive species and potential pest.