He cautioned, however, that urban forests are in grave danger. For every four trees that die, only one is planted and the average lifespan of a city tree, caused by excessive heat in summer and excessive salt in winter, is only 25 years. Planting native species is one of the best ways to attract a greater diversity of birds, small mammals and insects, such as butterflies to your garden. Native species are more immune to disease and drought, and usually do not require pesticides or herbicides. In Ontario, native tree species include Eastern white cedar, white spruce, maples, oaks and mountain ash.
Naturalists is a great place to start.
The Canadian Wildlife Federation is also working on a plant encyclopedia that will list native species for particular areas of the country. Occasionally, pets, particularly cats, and local wildlife will run into trouble if put too close together. Another suggestion was to spread a carpet of spruce boughs around areas to be protected. Cats dislike stepping on spruce boughs, although they will not harm the pads of their feet. Cats, and some dogs, don't like the smell of citrus fruits, so place orange, lemon or grapefruit rinds around bird feeders or particular shrubs to discourage pets.