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.