Trees provide birds with food, cover, nest sites and song posts. Food is available directly in the form of buds, seeds and fruit and indirectly as a result of the insect life that plants support. Some of our native trees such as oak, ash, birch and hawthorn support numbers of insects which in turn are a source of food for many species of birds such as tree creepers, blue tits, wrens and warblers. One in every two Irish insect species is dependent on these woodlands for their homes. Other birds like the blackbird, the thrush and the wood pigeon eat the berries and seeds of trees and shrubs during the winter when other food is scarce.
Trees also offer shelter from harsh weather and cover for nesting birds.
An old decaying tree with a hole or cavity in its trunk may become the home of an owl. Smaller holes may be used as nest sites by blue tits and great tits. Accumulated leaves on woodland floor are an ideal food for many species of insects which in turn are eaten by woodland birds. Well established woodland areas are also inhabited by mammals such as the fox, the red and grey squirrel and the red deer. The squirrel is the mammal most closely associated with trees.