Many of us have observed this by watching wild flocks actions in our own backyards. Pet owners, breeders, or scientists do not know exactly what is a perfect diet for any bird, though many do make claims. What the scientists do know and can share with us are the analysis of birds' stomach contents. The vitamin and mineral content have been estimated from the few examples offered. Observation of different species has also been a help.
Different species choose different foods to eat.
Many species can and will eat seeds, greens, earth and minerals from clay-like mounds. Some prefer a diet of nectar, while some include live insects or nuts to complete their diets. If the bill is long, slender and pointed it may be a nectar eater. These birds need a longer length bill to reach the bottom of a blossom to feed. There is also variety within this bill formation as well - various lengths, widths and thicknesses.