The modern approach to garden bird feeding is to use a range of foods that support the specific nutritional requirements of a wide range of species over the course of a year. There is a scientific evidence highlighting the positive effects that the provision of supplementary food can have on birds. For example, the provision of supplementary food has been shown to improve overwinter survival in a number of species.
What foods should I provide?
Many garden birdwatchers provide black sunflower seeds and sunflower hearts as their staple foods. Alongside these, quality peanuts, nyjer seed and high-energy seed mixes are all greatly appreciated. There are other foods, e.g. sultanas (soak in water first) that are good for ground-feeding Blackbirds, while pinhead oats are ideal for fine-billed Dunnocks (but should not be left out in wet weather). Windfall apples and small amounts of finely grated mild cheese can be very useful, particularly in the winter, while peanut cake (a mix of fats and peanut flour) will attract species like Long-tailed Tit. Fat smeared into cracks in tree bark will be found by Treeecreepers and woodpeckers (read summary of recent research into effects of providing fat-based foods). Live foods, such as mealworms, are expensive (though you can grow your own) but are readily taken by Robins, Blackbirds and Wrens.
Black sunflower seeds:
Black sunflower seed was introduced in the early 1990s and revolutionised bird feeding by providing a high energy food in a readily accessible form. Black sunflower seeds have thinner husks than the more traditional striped sunflower seeds and so are easily to split open. Black sunflower seeds are a favourite of Greenfinches and tits, though they may be shunned if sunflower hearts are available nearby. The downside of feeding these seeds is the pile of husks left below the feeder.
Sunflower hearts are more expensive than black sunflower seeds but they have two advantages. First, the birds can feed more quickly because they do not have to remove the husk. Second, the lack of the husk means that there is no unsightly pile of husks left behind on the ground after the birds have had their fill.
Seed mixes come in a vast range, differing in content and quality. Cheap mixes often have a high proportion of cereal. These larger grains are favoured by sparrows and pigeons. Better quality mixes have a lower cereal content and so are particularly suitable for finches and buntings. The best mixes are carefully balanced to cater for a range of species. Some now contain added suet pellets, fruit or pieces of mealworm.
Peanuts are high in oils and proteins and have been used for feeding birds form many decades. Always buy good quality peanuts from a reputable source and avoid any that show any signs of mould. Peanuts are best supplied behind a wire mesh so that a bird cannot take a whole peanut away. Keep you peanuts in a cool and dry environment and buy them in small quantities, so that they do not sit around for too long. Peanuts can be contaminated with a naturally occurring poison called aflatoxin.
Nyger, sometimes seen spelt nyjer or sold as 'thistle' seed, is a relatively new addition to the bird feeding market and it is one that initially found favour with Goldfinches - which seemed to like the small size of these seeds. Because these seeds are so small they have to be supplied in a specially adapted feeder. They are oil rich and ideal for birds with delicate bills. There is some suggestion that Goldfinches now favour sunflower hearts, only moving onto the nyger when competition on other feeders is great. However, this may just be a local effect.
Mealworms are not worms but the larval stage of a beetle. It is the larvae of the Yellow Mealworm Tenebrio molitor that are used widely as food for wild birds, as well as captive birds, reptiles and amphibians. Another less common but similar species, the Dark Mealworm Tenebrio obscura is sometimes used, the larva being somewhat smaller in size. Why not grow your own?
How much to feed and when
Try to balance the amount of food that you provide against the number of birds coming in to feed. In this way you will avoid creating a surplus of food that might go off or attract unwanted visitors, such as rats. Good practice is to clear your bird table down each night, removing uneaten food and any droppings.
Feeding throughout the year is recommended by conservation organisations, as it is not just during the winter that birds are under stress. If you are going away on holiday, then reduce the amount of food provided in the days leading up to your departure so the birds don't find that their favoured resource has suddenly disappeared.