Most insects will feed on a variety of foodstuffs during their lifecycle, but many will feed directly on plant material at some stage. In turn, insects are preyed upon by other insects and at some point in their development, both predator and prey become bird food.
The majority of insects need one or more food plants as larvae, and nectar from plants as adults. The wider the range of plants available, the wider the range will be of insects that inhabit your garden.
A wider range of insects in your garden will attract a greater range of visiting birds to feed on them. Flowers are present at most times of year in gardens, providing food over longer periods than natural habitats, making them a haven for insects. Gardens, with a higher proportion of native plants, such as wild flowers, are likely to attract more insects, as they are more easily recognisable and accessible than exotic species unfamiliar to our native insects.
Some insects eat dead or decaying plant matter, detritus. For this reason it is advisable not to clear away all dead garden material and seed heads as many insects depend on it for food or a place to hibernate during the winter months. A good idea is to leave piles of dead leafs in a heap under a bush instead of throwing them out. This will provide perfect shelter and food for wide variety of different insects.