Saturday, February 9, 2013

House Crow




Description

     The House Crow (Corvus splendens), also known as the 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 relatively 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.In the dry parts of South Asia and Iran the subspecies C. s. zugmayeri is found and this has a very pale neck collar. The nominate race is found in India, Nepal and Bangladesh and has a grey neck collar. In southern India, the Maldives (sometimes separated as maledivicus) and Sri Lanka, the subspecies C. s. protegatus is darker grey. The darkest form however is the Myanmar form C. s. insolens and lacks the grey collar.



Behavior, feeding and habitat

     It has a widespread distribution in southern Asia, being native to NepalBangladeshIndiaPakistanSri LankaMaldives and Laccadive Islands, South West Thailand and coastal southern Iran. It has been introduced to East Africa around Zanzibar (around 1897) and Port Sudan, and arrived in Australia via ship but has up to now been exterminated. Recently it has made its arrival in Europe and has been breeding in the Hook of Holland since 1998. An individual of this species has been present in Cork Harbour on the south coast of Ireland since early September 2010.In the New World, a small population of House Crows is established in the area around St. Petersburg, Florida.It is associated with human settlements in all of its range, from small villages to large cities. In Singapore there was a density of 190 birds/km2 in 2001 with efforts to suppress the population in planning.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.The invasive potential for the species is great all over the tropics. This species is able to make use of resources with great flexibility and appears to be associated with humans, and no populations are known to exist independently of humans.
     



     It feeds largely on refuse around human habitations, small reptiles and other animals such as insects and other small invertebrates, eggs, nestlings, grain and fruits. 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. It is a highly opportunistic bird and given its omnivorous diet, it can survive on nearly anything that is edible. These birds can be seen near marketplaces and garbage dumps, foraging for scraps.At least some trees in the local environment seem to be necessary for its successful breeding although they occasionally nest on telephone towers. It lays 3-6 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 was from April to July. Large trees with big crowns are preferred for nesting.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.The voice is a harsh kaaa-kaaaIt is suspected that paramyxoviruses, such as PMV 1 that causes of Newcastle disease may be spread by Corvus splendens. Outbreaks in India of Newcastle disease were often preceded by mortality in crows. They have also been found to carry Cryptococcus neoformans which can cause cryptococcosis in humans.Crows in Tanzania curiously showed an absence of blood parasites although some species such as Trypanosoma corvi have been first described from this species.



     I have been observing crows, almost every day at our house, and in many places in my city Mangalore. They have a typical way of posing for a camera, as per my personal observation. All the images posted here are full frame images and no cropping has been done on them. I have used a Canon EF 300mm F4L IS USM lens with Tamron 1.4x Extender on my Canon EOS 7D, which has helped me to get closer to this bird, as an experiment of the Tamron Extender. As you can see, my focal length has gone up by 1.4 times with an extender, but the sharpness still remains the same, which is the great advantage of owning a Prime Lens or Fixed Focal Length lens. Crows are friendly to humans, provided we are softer in approaching them. Birds observe humans a lot and I have been luckily getting closer poses of the House Crow. The minute they see me with the camera, they circle me in a group of 6 to 7, flying around me, untill I settle down and click them individually. It has been my personal observation of crows being friendly to humans. They visit our house, atleast 10 times a day, beginning from the morning. I am happy that they have given me some time to spend with them, when I am free at home.



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