Nest Site Selection by House Crows on Diamond Harbour Road in Kolkata, India

Surveys were conducted in the city of Kolkata to observe the patterns of nest site selection by the bird Corvus splendens (House Crow). The total study was carried out on the Diamond Harbour road of kolkata, West Bengal, India. Accordingly I had the chance to observe total 225 trees in which 196 trees had 105 nests and 29 trees were found without any nest of House Crow. I observed the nests both on the straight main road side and the corner sides of the main road.

The nesting site observations begun in the ending of March. The maximum numbers of nests were observed during the period of April-June. House crows were not always visible near their breeding sites and nests could be easily located by observing them from a certain distance. The data were collected during the breeding seasons from 2006 to 2007. Several features of the nesting sites were measured. The names of the species of all observed nesting trees both in straight main road sides and corner sides of the main road were identified.

Observations and Results

The nests of House crows is a gathering of twigs, usually found high upon a tree firmly lodged between the branching forks of tall trees. The breeding periods in 2006 and 2007 lasted for around 74 days and 81 days respectively. Through my study period House crows did not normally reuse the old nest after one breeding season. But they reused the nest building materials. The height of the nesting trees were ranged from 6m. to 24m.(average 16.82 ± 4.68 m.). The height of the nests above the ground was ranged from 4m to18m.(average 11.76 ± 4.69 m.). During the two years study, among the total 196 trees with nest, 148 trees (75.51%) were found on straight main road side and 48 trees (24.49%) were found at the corner sides of the main road. But, if I consider the total number of 225 observed trees then it will be revealed that out of 172 plants on straight main road side (SMRS) nests were found in 148 trees (86.04%), whereas out of 53 trees on corner sides of the main roads 48 trees (90.56%) were found with nest. So, the nesting density was found higher on the corner place of the road side considering the whole surveyed trees.

It was seen that, on SMRS House crows do not nest when : 1) there are overlapping branches of two trees, 2) one tree is situated at corner and others on SMRS, 3) a chemical factory is situated near a tree, 4) nest/nests other than crow is/are present on a tree, 5) two same trees are present side by side (not in all cases), 6) a bushy branch is present, 7) if the height of the tree is short etc. On corner sides, only a few plants were found without nests, where 1) the overlapping branches are present, 2) bushy branches of trees are present 3) if the height of the tree is short etc.

Sources of foods were found on survey areas involve :

1) Market places (mainly fish/meat market),

2) Dustbins on roads, municipality wastes,

3) Dead animals on roads and on open lands etc.,

4) Hospital wastes (food wastes of patients),

5) Wastes from schools and colleges,

6) Wastes from a home/house after enjoying a party throwing on roads.

Besides the above mentioned sources of food, House crows also wait for a chance of stealing/catching food from kitchen of home/house, market returning people carrying plastic bags with fishes/meats etc.

The names of the different trees where the nests of House Crows were observed on the Diamond Harbour Road of Kolkata, India, are given below :

a) Albezia lebbeck (Local Bengali term : Sirish)

b) Caeselpenia pulcherima (Local Bengali term : Krishnachura)

c) Delonix regia (Local Bengali term : Radhachura)

d) Alstonia scholaris (Local Bengali term : Chatim)

e) Ficus benghalensis (Local Bengali term : Bot)

f) Ficus religiosa (Local Bengali term : Assath)

g) Anthocephalus indicus (Local Bengali term : Kadam)

h) Acacia catechu (Local Bengali term : Khoer)

i) Eukalyptus sp. (Local Bengali term : Eukalyptus)

j) Mimosops elingii (Local Bengali term : Bakul)

k) Polyalthia longifolia (Local Bengali term : Debdaru)

l) Mangifera indica (Local Bengali term : Aam)

m) Terminalia arjuna (Local Bengali term : Arjun)

Discussion

It was revealed from my survey through the Diamond Harbour Road, (in the city of Kolkata, India) that House crows like to establish their nests on the corner sites of the main road, where two, three or more roads are crossed. This is probably due to the convenience of watching the source of food from various ways as well as to watch whether any danger is coming towards their nests because in this city persecution by human also observed by me. Sitting on a corner tree a House crow can watch the various sites of the different roads and it is easier for them to bring foods for young crows.

It was also seen that they like to nest usually on the tall trees to avoid the human persecution on the Diamond Harbour Road as well as to see the food sources from a good height.

Finally, we, the citizens of the different cities must take an oath after understanding the whole text that we must think about the conservation/protection of corner trees, and we should not cut any tree which may be a good house for a House Crow for its parental care to continue the existence of this species.