Because natural cover is so important to a successful backyard bird habitat, during deep winter is a good time to take stock of what’s already living in your yard, and what could be planted.
The best approach to this project is to make a rough drawing of the backyard, including all the large trees, small trees, large shrubs, small shrubs, and ground cover that already exist. Then, while looking at the drawing, ask yourself these questions: Are there enough shrubs close to the house, and near bird feeders and bird baths, to allow birds to escape into them should they be attacked by predators? Is there enough ground cover to allow birds that feed on the ground to escape predators? Are there enough large shade trees to provide adequate cover in the canopies for those species that nest and feed at the tops of trees?
Though it takes years for large trees to grow to maturity, any small trees, shrubs or ground cover added to the landscape will instantly improve the habitat for birds.
Ideally, a stadium effect should be created, with the largest trees farthest from the house and the ground cover closest to the house. The stadium effect provides several life zones, attracting a greater variety of birds, visible from the house.
Any plants that give birds both cover and food are the best ones to plant. Some examples are highbush cranberry, mountain ash, hawthorns, any nut producing tree, and trumpet vines.
-- George H. Harrison