Hole Nest in Trees

Holes in dead or alive trees are a good option for  nesting by birds .Fewer birds like the woodpeckers and Barbets excavate their own holes in trees for nest building.Most tree hole nesters make use of the already existing holes in large or small trees.Most common hole nesters are Parrots, common Starlings, Hornbills, Owls, Indian rollers and some flycatchers.The nest in tree holes has the define advantage of protection from predators and weathers.Birds do modify the tree holes like lining with soft materials or mud plastering  in case of Horn bills. However the disadvantage is that due to warm and humid conditions inside the holes there is more chances of avian pests and nest parasites build up.It is a wonder that The Great Indian Hornbill nearly a meter long in size  likes to nest at 20-45 meters up the tree .This means it can only  nest in trees which have a diameter greater than 1-2 meters at that height. As the large trees are fast decreasing in the forests, the existence of the Great Hornbill is now a concern.

Hole Nest in Ground

Very few birds nest within holes in the ground.Nesting in hole  seems to be a better strategy than nesting in the open.We survey around 100,000 eggs and found that non-hole nesters averaged 48% rearing success while hole nesters averaged 74%.The main reasons seems to be eggs within holes in the ground are better protected against adverse environmental conditions and from predators.The hole nests can be  open onto a cliff edge or a vertical edge of a river bank,Road cuttings and those holes in relatively flat ground.Some birds dig the holes themselves and some uses the already existing holes.Birds making this types of nest are green bee eater and all king fishers.Green bee eaters make almost 1 meter hole in flat ground as well as edges to lay their eggs.