Wildlife and Trees
Trees, and Plants serve a very important purpose when you take ecosystem into account. Many animals will find sources of food through the trees surrounding you. During the winter wildlife will often find suitable homes, or at least cover from harsh climates due to trees. Evergreens in particular do a fantastic job of this. Pine trees are one of the best examples of trees that provide shelters for birds. Furthermore, any tree with dense foliage, and complex branch networks in the crown will do a wonderful job of protecting life. Its more than simply allowing birds a strong structure to create the nest. Its also about protecting them from predators. Elevation, and food such as insects nearby play a huge role in this.
Often hollow ends of the tree trunk will become homes to woodpeckers, and squirrels. In many cases homeowners will add bird houses to make up for the lack of trunk cavities. A common tip given to property owners, is when landscaping to plant trees of varying heights. This is because trees and plants of different sizes will collect different nutrients at unique levels. Additionally, they will each add something new to the ecosystem.