They provide many and varied habitats for birds and other wildlife, the nest sites and song posts provided being of particular importance to birds. Directly or indirectly trees also offer food for birds. As the longest living organisms in the world, trees are primary producers, their leaves acting like a factory. This process is called photosynthesis and is used by all green plants to produce food. This food then becomes the basis of other food chains.
Trees require a variety of age structures and species for a woodland eco-system to work.
Seeds, saplings, standards, mature, over-mature and dead trees supply valuable food for birds, as well as the habitat which they need to survive. Redpolls and Crossbills . Food is also available indirectly from the insects which live in the trees. The Treecreepre picks insects out of cracks in the bark. Masses of caterpillars which feed on oak leaves in turn provide vital food for Great Tits and Blue Tits feeding their young in May and June.