Trees versus shrubs – Shrubs are often described as having multiple stems while trees have one. However, the line blurs and many woody plants we think of as shrubs are in fact small trees. In some cases they may be better suited for city planting given their relatively small size.
Think native – Although exotic ornamentals are widely planted and can attract wildlife, native species do a better job in the long run. By planting non-native species we always run the risk of these aliens escaping to surrounding habitats and out-competing native species. Common Buckthorn (Rhamnus frangula), Glossy Buckthorn (R. cathartica), and Tartarian Honeysuckle (Lonicera tartarica) have been widely planted in gardens, and are particularly invasive. They now frequently form the dominant shrub communities in many local natural areas. In some urban woodlots, native maples have been almost replaced by Norway Maple, which produces abundant and fast-growing seedlings. Other common invaders from our gardens include Black Locust (Robinia pseudoacacia), Japanese Knotweed (Polygynum cuspidatum), Chinese or Siberian Elm (Ulmus pumila) and Common Barberry (Berberis vulgaris).
Think thickets – Groups of trees and shrubs provide better wildlife habitat; even a small thicket of 3–5 trees underplanted with 3–6 shrubs is better than single trees spaced far apart. Variety is good. Different species provide different roosting and nesting habitats and also supply a greater variety of food, either directly by their fruits or indirectly by attracting a richer cocktail of insects. Thickets of a single species are not as attractive as those of mixed species.
Think hedgerows – Hedgerows, planted with the right mix of shrubs and trees can provide food, cover, nesting sites, and a corridor for safe passage from one habitat to another (Hanrahan 1999). [See also Creating a hedgerow for wildlife]
Many species of birds thrive in “edge” habitats, taking advantage of two types of plant communities. Hedgerows are, in effect, long strips of edge habitat.
Think snags – Where it is safe to do so, leaving standing dead trees (snags or wildlife trees) is one sure way to attract a variety of birds that both feed and nest in them (Hanrahan 1994). [See also Wildlife trees]
Think dual purpose – Trees and shrubs that offer both food and cover (for roosting and nesting) are the best value for you and the birds you want to attract.
Think site conditions – You need to know the conditions in your garden. Is it well-drained? Is it very dry or very damp? Sunny or shady? Is there room for several big trees or will there be potential problems? Suburban gardeners can often get away with planting more and bigger trees than urban dwellers, but this is not a hard and fast rule. All these considerations influence the types of species you can successfully plant.
Species and the birds they attract
I have listed only those species of birds that are likely to be found in urban settings, either because they breed there or are found during migration. Thus birds such as Ruffed Grouse, which feed on the buds of many trees but rarely enter urban areas, are not included. I have not included mammals. In our urbanscape we can take it for granted that squirrels (Grey and Red) will be attracted to many of the same trees that birds are. Cottontail Rabbits are becoming increasingly common in many residential areas of Ottawa and of course we have skunks and raccoons, and various other and sometimes surprising four-legged neighbours.
I’ve noted whether it is seeds, nuts, sap or fruit that primarily attracts birds. An asterisk (*) next to a bird species indicates that the tree/shrub is especially important as a food source. The list has been divided into species that grow best in sun and those that can tolerate shade to partial shade. Soil conditions and average height are also given. Some species can tolerate both dry and moist sites and this is also noted with the preferred conditions given first.
Soil conditions: W = wet, M = moist, D = dry