They will seek out and eat various insects and moluscs that could otherwise damage plant life.
However! ensure that you manage your garden in the most environmentally way possible.
For example; be as organic as you can, avoid the use of insecticides and other chemicals.
Laying out various bird feeds on bird tables/baths and purpose made feeders suspended from trees and fences is one useful way.
There are many types of bird food that can be purchased from specialist shops and garden centres.
If this is deemed too expensive there are a number of home made alternatives that can be used as seen in the following list:
Commercial seed mixes are readily available; some designed to attract specific bird types.
Finely chopped bacon rind is appreciated by many small birds as is grated cheese, grain, sunflower seed and nuts.
Blocks of fat can be purchased to either be suspended on cords or to fit into feeders.
You can make your own fat blocks by melting suet and pouring into moulds such as coconut shells or logs with holes drilled into them.
Adding commercial seed to the mix can put variety into the feeding process.
Fruit such as apples and raisins can be a useful addition to the menu.
Growing plants that hold onto their fruit/berries/seed during the winter months is another food source for birds.
Form habitats that benefit other forms of wildlife in to your garden.
This can be done by turning your garden into a small scale, bird-friendly nature reserve.
For example: do this by not over tidying the garden, or by forming wild areas such as a wild flower meadow to attract other wildlife in the food chain.
If these are subsequently used by the birds then the young birds will treat your garden as their home from the outset.
The secret is to get the birds into the habit of feeding in your garden all the year round and they will help you in return!