You can make your garden more attractive to birds, insects and small mammals in a variety of ways. Minor changes such as mowing less frequently can increase the number of non-human visitors to your yard, no matter its size.
A wildlife garden should provide for basic animal needs such as food, shelter and water. Diversity is the key to creating an optimum habitat. A diverse habitat attracts a wider variety of species, offers more choices for forage and shelter and ensures a constant food supply. Ideally, a garden should offer a mixture of meadow, woods and wet areas, but you can create hiding places and feeding areas without drastically changing your yard's character.
Your yard will attract different types of animals as the seasons change. Migratory species have different foraging needs than residential, non-migratory species. Larval stages of insects (such as caterpillars) often feed on completely different plants, or parts of plants, from what the adults prefer.
Watch birds and butterflies in the wild or on untended land to discover their food preferences. Select plants that maximize flowering and fruiting. Nectar-rich wildflowers are more nutritious for wildlife than showy cultivars, which often are sterile. Color attracts hummingbirds and butterflies. Hummingbirds prefer bright red and orange flowers, while butterflies seem to select yellow, purple, blue, pink, and occasionally red flowers. Members of the composite family, such as goldenrods, sunflowers and thistles are good nectar sources for butterflies, and later form seedheads that attract goldfinches and other songbirds.
Be sure to include trees and shrubs with berries to provide winter forage for birds and small mammals. Vines and grasses provide food and nesting materials. Other provisions you can offer residential or transient wildlife include pollen, fungi and sap from native plants or compost.
Try to create a layered effect when planning shelter for wildlife. Wooded areas should include overlapping canopies of trees, shrubs and forbs. The edges of woods are usually rich with wildlife because the cover protects them from predators and the elements.
When designing shelter areas, shrubs may be more important than trees because they grow faster and provide nesting sites for many different species. To provide maximum cover, curb your pruning impulses! Though dense shrubbery, tangled vines and dead-standing trees may contradict your image of an orderly yard, they create ideal nesting and forage sites.
Even in a small yard, a single tree or a few vines can provide shelter for nesting wrens or blackbirds, as well as cover for snails and butterflies. Don't overlook what's underfoot - brush piles, hollow logs, and compost piles offer a host of microhabitats for many organisms.
A significant portion of wildlife activity centers around water. A water source such as a small pond provides a home for amphibians and aquatic insects, a bathtub for birds and drinking water for all kinds of creatures. Many insects have aquatic larval stages, so they need to be near water. Migrating wildlife need convenient water sources along their seasonal routes. On the smallest scale, even a birdbath is a valuable addition to your garden or yard.
Once you allow wildlife into your garden, you must allow nature a bit of freedom in ruling it. As Chris Baines, an innovative British landscaper, notes, the secret of a successful wildlife garden depends on understanding the way in which your various gardening activities will distort the balance. Try to minimize disturbance. Refrain from using herbicides, pesticides, or fungicides, which adversely affect the delicately balanced interactions between organisms and their environment. Allowing your garden more autonomy will leave you plenty of time to observe, enjoy and learn from your creation.